Agriculture and the plow originated 10–13 millennia ago in the Fertile Crescent of the Near East, mostly along the Tigris, Euphrates, Nile, Indus and Yangtze River valleys, and were introduced into Greece and southeastern Europe ∼8000 years ago. The wooden plow, called an ard, evolved into the “Roman plow”, with an iron plowshare, described by Virgil around 1 ad and was used in Europe until the fifth century. It further evolved into a soil inverting plow during the 8th to 10th century. In the U.S., a moldboard plow was designed by Thomas Jefferson in 1784, patented by Charles Newfold in 1796, and marketed in the 1830s as a cast iron plow by a blacksmith named John Deere. Use of the plow expanded rapidly with the introduction of the “steam horse” in 1910 that led to widespread severe soil erosion and environmental degradation culminating in the Dust Bowl of the 1930s. A transition from moldboard plow to various forms of conservation tillage began with the development of 2,4-D after World War II. No-till is presently practiced on about 95 million hectares globally. No-till technologies are very effective in minimizing soil and crop residue disturbance, controlling soil evaporation, minimizing erosion losses, sequestering C in soil and reducing energy needs. However, no-till is effective only with the use of crop residue as mulch, which has numerous competing uses. No-till farming can reduce yield in poorly drained, clayey soils when springtime is cold and wet. Soil-specific research is needed to enhance applicability of no-till farming by alleviating biophysical, economic, social and cultural constraints. There is a strong need to enhance sustainability of production systems while improving the environmental quality.
Integrated crop–livestock management systems (ICLS) have been increasingly recommended in Brazilian agroecosystems. However, knowledge of their effect on soil organic carbon (SOC) and total nitrogen (TN) concentrations and stocks is still limited. The study was undertaken to evaluate the effects of ICLS under two tillage and fertilization regimes on SOC and TN concentrations and stocks in the 0–30 cm soil layer, in comparison with continuous crops or pasture. The following soil management systems were studied: continuous pasture; continuous crop; 4 years’ crop followed by 4 years’ pasture and vice-versa. The adjacent native Cerrado area was used as a control. Under the rotation and continuous crop systems there were two levels of soil tillage (conventional and no-tillage) and fertility (maintenance and corrective fertility). The stock calculations were done using the equivalent soil mass approach. The land use systems had a significant effect on the concentrations of SOC and TN in the soil, but no effect was observed for the soil tillage and fertilizer regimes. For these two latter, some significant discrepancies appeared in the distribution of SOC and TN concentrations in the 0–30 cm layer. Carbon storage was 60.87 Mg ha−1 under Cerrado, and ranged from 52.21 Mg ha−1 under the ICLS rotation to 59.89 Mg ha−1 with continuous cropping. The decrease in SOC stocks was approximately 8.5 and 7.5 Mg ha−1, or 14 and 12%, for continuous pasture and ICLS respectively. No-tillage for 10 years after the conversion of conventional tillage to no-tillage under the continuous crop system, and 13 years of conventional tillage in continuous cropping did not result in significant changes in SOC stocks. The SOC and TN stocks in surface layers, using the equivalent soil mass approach rather than the equivalent depth, stress the differences induced by the calculation method. As soil compaction is the principal feature of variability of stocks determinations, the thickness should be avoid in these types of studies.
Caesium-137 measurements have been used to document changes in the rate and extent of soil erosion associated with the shift from conventional tillage to a no-till system on a farm in south-central Chile. The study site is located in the Coastal Mountains of the 9th Region (38°37′S 73°04′W), and is characterized by Araucano series Ultisols (Typic Hapludult), a temperate climate and a mean annual precipitation of 1100 mm year−1. A field, which was under conventional tillage until May 1986 and which was subsequently managed using a no-till system, was selected for the study. An approach for using 137Cs measurements to quantify the medium-term erosion and deposition rates associated with the periods of contrasting land management documented previously was employed. This approach involves both a standard method and a simplified method, which permits a larger number of sampling points to be used. In this study, emphasis was placed on application of the simplified method, which has the important advantage of requiring only two 137Cs measurements per sampling point. The results obtained for the study field showed that the implementation of no-till practices, including crop residue management, coincided with a reduction in the net erosion rate by about 87% and the proportion of the study area subject to erosion from 100% to 57%, and therefore significantly decreased soil and nutrient loss. Reduced soil and nutrient loss has important on-site benefits, in terms of sustainable management of the soil resource and maintaining crop productivity, as well as reducing off-site problems associated with the degradation of river water quality.
Distributed erosion and sediment yield models are being increasingly used for predicting soil erosion and sediment yields in agricultural catchments. In most applications, validation of such models has commonly been restricted to comparison of the predicted and measured sediment output from a catchment, because spatially distributed information on rates and patterns of soil redistribution within the catchment has been lacking. However, such spatially distributed data are needed for rigorous model testing, in order to validate the internal functioning of a model and its applicability at different spatial scales. The study reported in this paper uses two approaches to test the performance of the agricultural non-point source pollution (AGNPS) and areal non-point source watershed environmental response simulation (ANSWERS) erosion and sediment yield models in two small catchments in Devon, UK. These involve, firstly, comparison of observed and predicted runoff and sediment output data for individual storm events monitored at the basin outlets and, secondly, information on the spatial pattern of soil redistribution within the catchments derived from measurements. The results obtained indicate that catchment outputs simulated by both models are reasonably consistent with the recorded values, although the AGNPS model appears to provide closer agreement between observed and predicted values. However, the spatial patterns of soil redistribution and the sediment delivery ratios predicted for the two catchments by the AGNPS and ANSWERS models differ significantly. Comparison of the catchment sediment delivery ratios and the pattern of soil redistribution in individual fields predicted by the models with equivalent information derived from measurements indicates that the AGNPS model provides more meaningful predictions of erosion and sediment yield under UK conditions than the ANSWERS model and emphasises the importance of using information on both catchment output and sediment redistribution within the catchment for model validation.
Scientific, political, and social interests have developed recently in the concept of using agricultural soils to sequester carbon. Studies supporting this concept indicate that soil erosion and subsequent redeposition of eroded soils in the same field may establish an ecosystem disequilibrium that promotes the buildup of carbon on agricultural landscapes. The problem is to determine the patterns of soil erosion and redeposition on the landscape and to relate these to soil carbon patterns. Radioactive () can be used to estimate soil erosion patterns and, more importantly, redeposition patterns at the field level. The purpose of this study was to determine the relationship between , soil erosion, and soil carbon patterns on a small agricultural watershed. Profiles of soils from an upland area and soils in an adjacent riparian system were collected in 5 cm increments and the concentrations of and carbon were determined. and carbon were uniformly mixed in the upper 15–20 cm of upland soils. (Bq g−1) and carbon (%) in the upland soils were significantly correlated (r2=0.66). Carbon content of the 0–20 cm layer was higher (1.4±0.3%) in areas of soil deposition than carbon content (1.1±0.3%) in areas of soil erosion as determined by the technique. These data suggest that measurements of in the soils can be useful for understanding carbon distribution patterns in surface soil. Carbon content of the upland soils ranged from 0.5 to 1.9% with an average of 1.2±0.4% in the 0–20 cm layer while carbon below this upper tilled layer (20–30 cm) ranged from 0.2 to 1.5% with an average of 0.5±0.3%. Total carbon was 2.66 and 3.20 kg m−2 in the upper 20 cm and upper 30 cm of the upland soils, respectively. Carbon content of the 0–20 cm layer in the riparian system ranged from 1.1 to 67.0% with an average 11.7±17.1%. Carbon content below 20 cm ranged from 1.8 to 79.3% with an average of 18.3±17.5%. Soil carbon in the upper 20 cm of the riparian profile was 10.1 and 15.0 kg m−2 in the upper 30 cm of the riparian profiles. This is an increase of organic carbon by a factor of 3.8 and 4.7 for the upper 20 cm and upper 30 cm of the riparian profiles, respectively, when compared to the upland soil profiles.
Measured 137Cs losses (Bq m−2) from long-term runoff plots under tropical conditions and correspondent estimated soil erosion rates (Mg ha−1 year−1) were significantly correlated to directly measured soil losses of the same plots, during the same period (1963–2002). A tendency of higher 137Cs activities was observed in soil profiles of the bottom third part of runoff slopes that could be explained by the restricting effect of the collector system on the runoff flow or by tillage translocation. Despite of the very low 137Cs activity found in the soil of the plots, the isotopic technique yielded confident results, comparable to those obtained by the traditional direct measurements.
The spatial variation of soil erosion and deposition rates was studied in a small catchment cultivated by rainfed agriculture, in the Mouriki area, Viotia Greece, using the technique. A 25 m grid was established parallel to the slope and the inventories were defined for the grid points. After establishing the local reference inventory, the soil erosion and deposition rates were estimated using the residuals for individual points on the grid in conjunction with the four conversion (calibration) models described by Walling and He (2001) [Models for converting measurements to estimates of soils redistribution rates on cultivated and uncultivated soils]. The conversion models were validated by means of sensitivity analysis and using local experimental data. The resulting estimates of soil redistribution rates were interpolated by means of kriging, using Surfer Golden software. The magnitude of the soil erosion rates depend on many factors, including the location of the sampling point, the local slope, and the soil properties. The mass balance model 2 (MBM2) and mass balance model incorporating soil movement by tillage (MBM3) conversion models predict soil redistribution rates of the same order of magnitude as the experimental data and are able to take account of Chernobyl fallout. Predicted soil erosion rates for catchment grid varied from 6.71 to 85.55 t ha−1 per year using MBM2 and from 3.54 to 95.78 t ha−1 per year using MBM3. Deposition rates varied from 1.23 to 168.19 t ha−1 per year using MBM2 and from 3.24 to 189.18 t ha−1 per year using MBM3. High correlation was apparent between erosion/deposition rates (MBM2) and soil P (P<0.001), soil K (P<0.001), soil organic matter % (P<0.05), point slope (P<0.05), clay % (P=0.053) and altitude (P=0.057). The total soil losses from the catchment have been estimated at 18.34 t ha−1 per year using MBM2 and 22.12 t ha−1 per year using MBM3.
Studying on spatial and temporal variation in soil organic carbon (SOC) is of great importance because of global environmental concerns. Tillage-induced soil erosion is one of the major processes affecting the redistribution of SOC in fields. However, few direct measurements have been made to investigate the dynamic process of SOC under intensive tillage in the field. Our objective was to test the potential of 137Cs and 210Pbex for directly assessing SOC redistribution on sloping land as affected by tillage. Fifty plowing operations were conducted over a 5-day period using a donkey-drawn moldboard plow on a steep backslope of the Chinese Loess Plateau. Profile variations of SOC, 137Cs and 210Pbex concentrations were measured in the upper, middle and lower positions of the control plot and the plot plowed 50 times. 137Cs concentration did not show variations in the upper 0–30 cm of soil whereas 210Pbex showed a linear decrease (P < 0.05) with soil depth in the upper and middle positions, and an exponential decrease (P < 0.01) at the lower position of the control plot. The amounts of SOC, 137Cs and 210Pbex of sampling soil profiles increased in the following order: lower > middle > upper positions on the control plot. Intensive tillage resulted in a decrease of SOC amounts by 35% in the upper and by 44% in the middle positions for the soil layers of 0–45 cm, and an increase by 21% in the complete soil profile (0–100 cm) at the lower position as compared with control plot. Coefficients of variation (CVs) of SOC in soil profile decreased by 18.2% in the upper, 12.8% in the middle, and 30.9% in the lower slope positions whereas CVs of 137Cs and 210Pbex decreased more than 31% for all slope positions after 50 tillage events. 137Cs and 210Pbex in soil profile were significantly linearly correlated with SOC with R2 of 0.81 and 0.86 (P < 0.01) on the control plot, and with R2 of 0.90 and 0.86 (P < 0.01) on the treatment plot. Our results evidenced that 37Cs and 210Pbex, and SOC moved on the sloping land by the same physical mechanism during tillage operations, indicating that fallout 137Cs and 210Pbex could be used directly for quantifying dynamic SOC redistribution as affected by tillage erosion.
This paper presents the results of using the technique to assess soil erosion rates of both sloping cultivated land and flat terraces in the Upper Yangtze River Basin, China. The study was carried out on eighteen sloping cultivated fields and four flat terrace fields in eight counties and cities over the eastern part of the basin. The -reference inventory ranged from 620.5 to 2573.2 Bq/m2. For the 18 sloping cultivated fields, the average inventory over a field ranged from 204.9 to 1847.7 Bq/m2, which accounts for 15–77% of the local reference inventory, and the average water erosion rate ranged from 758 to 9854 t/km2 per year, with erosion rates of <1000 t/km2 per year in two fields; 1000–5000 t/km2 per year in eight fields; and >5000 t/km2 per year in eight fields. It is apparent that most of the sloping cultivated fields suffer severe or very severe soil erosion. For the four terrace fields under this study, the average inventory over a field ranged between 915.8 and 2675.4 Bq/m2, which accounts for 97–104% of the local reference inventory. However, water erosion is very slight on the terrace fields and little soil is lost from the terraces. The study also indicated that the severity of soil erosion is strongly related to soil texture and slope gradient.
The purpose of this research was to evaluate the applicability of conventional sampling and a simplified approach, for estimating medium-term tillage- and water-induced soil erosion and sedimentation rates on agricultural land in Chile. For this purpose, four study sites under contrasting land use and management were selected in central-south Chile. First, a conventional approach, based on grid sampling was applied, adapting a mass balance conversion model incorporating soil movement by tillage to the site specific conditions of the study region. Secondly, using the same conversion model, the feasibility of estimating soil redistribution rates from measurements of inventories based on composite soil samples taken along contour lines was also tested at all four sites. The redistribution rates associated with tillage and water and the total rates estimated using both methods correlated strongly at all four sites. The conventional method provides more detailed information concerning the redistribution processes operating over the landscape. The simplified method is suitable for assessing soil loss and sediment accumulation in areas exhibiting simple topography and almost similar slopes along the contour lines. Under these conditions, this method permits faster estimation of soil redistribution rates, providing the possibility of estimating soil redistribution rates over larger areas in a shorter time. In order to optimise the costs and benefits of the methods, the sampling and inventory quantification strategy must be selected according to the resolution of the required information, and the scale and complexity of the landscape relief. Higher tillage- and water-induced erosion rates were observed in the annually ploughed cropland sites than in the semi-permanent grassland sites. Subsistence managed crop and grassland sites also show greater erosion effects than the commercially managed sites. The methods used permit discrimination between redistribution rates observed on agricultural land under different land use and management. The technique must be seen as an efficient method for estimating medium-term soil redistribution rates, and for planning soil conservation and sustainable agricultural production under the climatic conditions and the soil type of the region of Chile investigated.
The Savanna region of Central Brazil is currently the most important area for grain production in the country but intensive agricultural activities are related to high losses of soil organic carbon. No-tillage systems were introduced in the mid 1980’s but the use of cover plants in no-tillage systems is poorly studied and there is a demand for selection of suitable species to improve soil organic carbon. This study characterizes the chemical composition of decomposing plant residues of different cover plants (Crotalaria juncea, Canavalia brasiliensis, Cajanus cajan, Mucuna pruriens, Helianthus annuus, Pennisetum glaucum, Raphanus sativus and natural fallow, as a control). Cover plants were used in rotation with maize, under conventional and no-tillage systems. Decomposition rates were estimated using litter bags and residues of C. juncea, C. brasiliensis, M. pruriens and R. sativus were analyzed by CPMAS 13C NMR. The highest decomposition rates were found for C. brasiliensis and C. juncea, while the lowest for M. pruriens, C. cajan and P. glaucum. C. cajan presented the lowest content of polysaccharides and along with M. pruriens, the highest percentage of aromatic C, reflecting the slow decomposition of highly lignified material. The residues of these two species also presented high hydrophobicity, as a consequence of the presence of aromatic groups. Incorporation of plant residues accelerated the decomposition in comparison to no-tillage system. C. cajan, P. glaucum and M. pruriens are more appropriate to increase soil cover due to lower decomposition rates while C. brasiliensis, R. sativus and H. annus, which presented higher decomposition rates, are indicated for an improvement of nutrient availability.
Long-term field experiments are among the best means to predict soil management impacts on soil carbon storage. Soil organic carbon (SOC) and natural abundance 13C (δ13C) were sensitive to tillage, stover harvest, and nitrogen (N) management during 13 years of continuous corn (Zea mays L.), grown on a Haplic Chernozem soil in Minnesota. Contents of SOC in the 0–15 cm layer in the annually-tilled [moldboard (MB) and chisel (CH)] plots decreased slightly with years of corn after a low input mixture of alfalfa (Medicago sativum L.) and oat (Avena sativa L.) for pasture; stover harvest had no effect. Storage of SOC in no-till (NT) plots with stover harvested remained nearly unchanged at 55 Mg ha−1 with time, while that with stover returned increased about 14%. The measured δ13C increased steadily with years of corn cropping in all treatments; the NT with stover return had the highest increase. The N fertilization effects on SOC and δ13C were most evident when stover was returned to NT plots. In the 15–30 cm depth, SOC storage decreased and δ13C values increased with years of corn cropping under NT, especially when stover was harvested. There was no consistent temporal trend in SOC storage and δ13C values in the 15–30 cm depth when plots received annual MB or CH tillage. The amount of available corn residue that was retained in SOC storage was influenced by all three management factors. Corn-derived SOC in the 0–15 cm and the 15–30 cm layers of the NT system combined was largest with 200 kg N ha−1 and no stover harvest. The MB and CH tillage systems did not influence soil storage of corn-derived SOC in either the 0–15 or 15–30 cm layers. The corn-derived SOC as a fraction of SOC after 13 years fell into three ranges: 0.05 for the NT with stover harvested, 0.15 for the NT with no stover harvest, and 0.09–0.10 for treatments with annual tillage; N rate had no effect on this fraction. Corn-derived SOC expressed as a fraction of C returned was positively biased when C returned in the roots was estimated from recovery of root biomass. The half-life for decomposition of the original or relic SOC was longer when stover was returned, shortened when stover was harvested and N applied, and sharply lengthened when stover was not harvested and N was partially mixed with the stover. Separating SOC storage into relic and current crop sources has significantly improved our understanding of the main and interacting effects of tillage, crop residue, and N fertilization for managing SOC accumulation in soil.
This study illustrated how crop residue-derived carbon interacts with non-residue carbon (e.g., native soil carbon) in agroecosystems and how carbon is allocated to soil organisms and respiration under different tillage regimes. The carbon dynamics in crop residue, soil microorganisms, nematodes and respiration were monitored using 14C-labeled corn residue. In addition, the carbon budget was estimated for both conventional tillage (CT) and no-till (NT) agricultural ecosystems during the short period after residue application. A laboratory and a field study were conducted separately to assess the above objectives. The results illustrated that the general patterns of carbon allocation were similar in both laboratory and field studies but at a lower magnitude in the field. Most 14C input to soil was released into air through soil respiration (93–98%) under both CT and NT regimes, with only a small portion bound in microbial (1.8–6.5%) and nematode biomass (0.01–0.12%). However, more 14C was retained in microbial and nematode biomass under CT than under NT, while the 14C distributed in soil respiration was similar under both tillage regimes. The 14C specific activities of soil microorganisms, nematodes and respiration were significantly higher under CT than under NT. The higher 14C specific activities of soil microorganisms and nematodes, and more 14C retained in the biomass of soil microorganisms and nematodes under CT, suggested that soil organisms might use C more efficiently under CT than under NT. During the short-term experiments, cumulative soil respiration was significantly higher but residue-derived carbon contributed less to soil respiration under NT than under CT. Consequently, more non-residue carbon (e.g., native soil carbon) was decomposed and respired by soil organisms under NT than under CT after 40 days of the residue application. It is suggested that residue application might cause a net loss of soil carbon in agroecosystems possibly because of the priming effect of crop residue, particularly under NT regime under the short term.
Returning crop residues to soil helps to maintain soil C stocks. Organic C stocks and microbial biomass are important factors controlling the decomposition or retention of crop residues in soil and the formation of aggregates. Little is known about the specific contribution of crop residues to soil aggregate size fractions in the framework of long-term fertilization. This study investigated the effects of long-term fertilization on the decomposition of 14C-labelled plant residues and their incorporation into soil organic matter (SOM) of different aggregate size fractions. Soils were collected from 0–10 cm in the Ap horizon of a long-term (since 1988) field experiment at Grossbeeren (Germany). The following four fertilization treatments were used: 1) without fertilization or manuring (Control), 2) nitrogen applied by mineral fertilizer (N), and 3) manure with low (M) and 4) high (2 M) application doses. Soils were incubated for 100 days at 20 °C, with or without 14C-labelled plant residue. The incorporation of 14C into three aggregate size fractions–large macroaggregates (2–1 mm), small macroaggregates (1–0.25) and microaggregates (<0.25 mm)–was analyzed.After 15 days of incubation, 44–57% of plant residue was mineralized in the order: M > N > control soil > 2 M. Adding plant residues increased soil β-glucosidase activity and microbial biomass C. On day 16 of incubation, more residue 14C was retained in small and large macroaggregates than in microaggregates in the control soil. In contrast, in fertilized soils the reverse was measured. Additionally, N, M and 2 M soils showed significant differences by incorporation of 14C in microbial biomass and β-glucosidase activity in different aggregate size fractions. The results imply that long-term fertilization significantly increased the residue 14C retention in microaggregate size fractions and its decomposition in soils.
Changes in some soil chemical, including 15N values, and biochemical properties (microbial C, FDA hydrolysis, glucosidase and urease activities) due to two tillage systems, conventional tillage (CT) and no-tillage (NT), were evaluated in an acid soil from temperate humid zone (NW of Spain) and compared with values obtained for a reference forest soil. The results showed that in the surface layer (0–5 cm depth) tillage tended to increase soil pH and to decrease organic matter levels and microbial biomass and activity values. The data also indicated that 8 years of NT, compared to CT, resulted in greater organic matter content and increased microbial biomass and activity, the changes being more pronounced for the microbial properties. Adoption of NT resulted in an increase of soil C storage of 1.24 Mg C ha−1 year−1 with regard to CT. The suitability of 15N as a potential tracer of land-use in this acid soil was also confirmed.
Zero-tillage (ZT) farming systems offer the potential of reducing soil erosion and conserving soil moisture on the semi-arid regions of the Canadian prairie. Since changes in soil tillage may alter the soil condition and environment, field experiments were conducted to assess the effect of ZT on spring wheat growth and 15N urea utilization and recovery. The study compared ZT and conventional shallow tillage (ST, 10 cm) systems, of 2–16-year duration, situated on a range of Chernozemic soils. Generally, ZT produced similar grain and straw yields as the ST; incidences of reduced yield under ZT were associated with poor seedling establishment. Characteristic lower soil temperature (1–4°C in seed row at 5-cm depth) under ZT was not related to crop yield, except for reduced early growth at one site. Soil moisture (to 120 cm) was similar between tillage systems, although moisture variations at the soil surface (0–5 cm), associated with differences in surface mulch, were apparent. Plant uptake of P and K was similar between tillage systems. Differences in N concentration, plant uptake of soil and fertilizer N and indices of available soil N between tillage systems over the growing season, tended to be small and did not differ substantially, although site or location differences were evident. Overall N yield was mainly related to the ability of the plant to utilize N for growth and plant yield. Recovery of the fertilizer N in the soil-plant system was not related to differences in soil tillage.
Soil organic matter is an ecosystem component with agronomic and environmental functions and is affected by soil management. The objectives of this study were to evaluate (i) soil organic C and N losses during a period of conventional cultivation (1969–1983) that followed on native grassland and (ii) the potential of four long-term (17 years) no-till cereal- and legume-based cropping systems (bare soil, oat (Avena strigosa Schreb.)/maize (Zea mays L.), lablab (Lablab purpureum L. Sweet) + maize and pigeon pea (Cajanus cajan L. Millsp.)+maize) with different N fertilisation levels (0 and 180 kg N ha−1 year−1) to increase the C and N stocks of a southern Brazilian Acrisol. Samples were taken from 0 to 107.5 cm depth, in 10 soil layers. The C content in the 0–17.5 cm layer of grassland decreased by 22% (8.6 Mg C ha−1) during the period of conventional cultivation. Meanwhile, N decreased by 14% (0.44 Mg N ha−1). Additional C and N losses occurred after the establishment of bare soil and oat/maize (no N). With N fertilisation, the C and N stocks of oat/maize were steady with time. Legume-based cropping systems (lablab + maize and pigeon pea + maize) increased C and N stocks due to the higher residue input. Although the major soil management effects were found in the 0–17.5 cm layer, up to 24% of the overall C losses and up to 63% of the gains of the whole 0–107.5 cm layer occurred below the 17.5 cm depth, reinforcing the importance of subsoil as a C source or sink. The average C sequestration rate of legume-based cropping systems (with N) was 0.83 Mg C ha−1 year−1 in the top 0–17.5 cm layer and 1.42 Mg C ha−1 year−1 in the whole 0–107.5 cm layer, indicating the remarkable potential of legume cover crops and N fertilisation under no-tillage to improve SOM stocks and thus, soil and environmental quality in humid subtropical regions.
The effect of ploughing depths, seedbed preparation and nitrogen fertilisation on a loam soil (fluvaquentic humaquept) were investigated in a factorial field experiment on a loam soil at Ås in southeastern Norway. The experiment was established in the autumn of 1939, reorganised in 1962 and was completed in the autumn of 1990. The working depths for ploughing (12, 18 and 24 cm) and seedbed cultivation (4, 8 and 12 cm) were constant during the whole research period. Different nitrogen application rates (50, 100, 150 kg ha−1) and seedbed preparation implement treatments (S-tine vs. rotary cultivator) were superimposed on the experiment in a factorial configuration in 1962. Since 1962 the main crops have been barley (Hordeum vulgare L.), oats (Avena sativa L.) and ley (timothy (Phleum pratense L.) and red clover (Trifolium pratense L.)).The yield loss for shallow ploughing (12 cm) was most pronounced in years with high weed infestation and at low nitrogen application rate (50 kg ha−1). Shallow harrowing with an S-tine cultivator (4 cm, one pass) significantly reduced cereal yields compared with more intensive and deeper cultivation.The soil structure measured from 1968 to 1987 appeared to be slightly better with regard to plant growth requirements after shallow (12 cm) compared with deep (24 cm) ploughing. Bulk density was lower and the porosity greater in the 7–11 cm layer after shallow compared with deep ploughing. The modulus of rupture increased significantly with ploughing depth. The amount of organic matter at the 0–40 cm depth was not influenced by ploughing depth. However, the content of organic matter in the surface layer was greater after shallow ploughing. Mineralisation of organic matter was estimated to be about 36 kg N ha−1 year−1 greater for a nitrogen application rate of 50 kg ha−1 compared with 150 kg ha−1. In the 0–40 cm layer the amount of organic matter on average decreased by about 1650 kg ha−1 year−1 from 1944 to 1987.
From 1977 to 1984, the influence of tillage and cover crops on soil erosion and yield of main crops was studied on Oxisols in Paraná, Brazil. Tillage systems were no-tillage (NT), minimum tillage with a chisel plough (CP) and conventional tillage with a disc plough (CT). It was found that under NT, as compared to CT and CP, the total pore volume and coarse pore volume were lower, bulk density in the upper soil layer was higher, available moisture was higher, temperature was lower and infiltrability was higher. Percentage of soil cover was the main factor governing infiltration rate. Without soil cover the infiltration rate under NT was the same as under CP and CT. The use of cover crops and crop rotation had a marked positive effect on maize, soya bean and bean yields. Yields of wheat and soya beans were higher under NT and CP. It is concluded that in Paraná no-tillage in combination with adapted cover crops and crop rotations represents a production system which is efficient in reducing water runoff and consequently soil erosion, and in increasing crop yields.
On Oxisols (Latosolo Roxo; LR) and Alfisols (Terra Roxa; TR) in the North of Paraná, current tillage practices have destroyed the natural high structural stability and have caused soil compaction in the lower part of the Ap-horizon, resulting in serious soil erosion. Efficient erosion control can be achieved by cover crops, which increase permeability and water infiltration rates through the biological loosening effect of the root system. Another possibility for efficient erosion control was shown to be the no-tillage technique. Due to a higher soil moisture content, lower soil temperature, especially at sowing, and higher biological activity of the soil, yields of wheat and soybeans were usually higher in the no-tillage system than under conventional tillage, especially in a dry year. At one site, where no-tillage was performed without the use of herbicides, wheat yield was reduced due to weed competition. Some cover crops, direct-drilled into soybean stubble, produced during winter more than 6 t/ha of dry matter.
Commercial potato production in the UK requires considerable traffic associated with primary and secondary cultivations and harvesting with consequent problems of topsoil compaction. The extent of these soil and crop effects were examined for a conventional traffic system and for an experimental zero traffic system which was developed from standard machines modified to have all wheels running on permanent wheeltracks at 2.8 m centres. Three rows of potatoes were grown between the wheeltracks, the central row only being traffic-free, as the edge effects of the wheeltracks influenced the outer rows. Results for three seasons showed that the zero system gave mean increases of 14% and 18% in total and marketable potato yields, respectively, as a result of greater soil air-filled porosity in wet seasons and lower soil strength in dry seasons. During harvest, the conventional system produced 30% more soil clods and, after harvest, required a 70% greater draught force for cultivation. Commercial exploitation of the zero system will depend on the development of an economically viable, wide-track machine.
Soil erosion is a major threat to global economic and environmental sustainability. This study evaluated long-term effects of conservation tillage with poultry litter application on soil erosion estimates in cotton (Gossypium hirsutum L.) plots using RUSLE 2.0 computer model. Treatments consisting of no-till, mulch-till, and conventional tillage systems, winter rye (Secale cereale L.) cover cropping and poultry litter, and ammonium nitrate sources of nitrogen were established at the Alabama Agricultural Experiment Station, Belle Mina, AL (34°41′N, 86°52′W), beginning fall 1996. Soil erosion estimates in cotton plots under conventional tillage system with winter rye cover cropping declined by 36% from 8.0 Mg ha−1 year−1 in 1997 to 5.1 Mg ha−1 year−1 in 2004. This result was largely attributed to cumulative effect of surface residue cover which increased by 17%, from 20% in 1997 to 37% in 2004. In conventional tillage without winter rye cover cropping, soil erosion estimates were 11.0 Mg ha−1 year−1 in 1997 and increased to 12.0 Mg ha−1 year−1 in 2004. In no-till system, soil erosion estimates generally remained stable over the study period, averaging 0.5 and 1.3 Mg ha−1 year−1with and without winter rye cover cropping, respectively. This study shows that cover cropping is critical to reduce soil erosion and to increase the sustainability of cotton production in the southeast U.S. Application of N in the form of ammonium nitrate or poultry litter significantly increased cotton canopy cover and surface root biomass, which are desirable attributes for soil erosion reduction in cotton plots.
Modern no-tillage techniques are being practiced worldwide on more than 100 million hectares of land. Despite proven advantages, reduced tillage (RT) is used only on 25% of agricultural land in Germany and direct seeding (DS) is not at all practised. Therefore, a trial was performed at the Leibniz Centre for Landscape Research (ZALF e. V.) from 2002 to 2005 to compare conventional tillage (CT), RT and DS practices in the following crop rotation: winter rape (Brassica napus L.) – winter wheat (Triticum aestivum L.) – maize (Zea mays L.) – winter wheat – winter barley (Hordeum vulgare L.) (in DS: winter wheat). The study was aimed at determining the profitability (net return) of these methods under on farm conditions.The application of RT proved to be the most competitive system with the highest net return of 111 euro ha−1 recorded at the midpoint of the 4-year trial period. The system of CT in contrast produced −7 euro ha−1 at the midpoint of this trial period, yielding the poorest results. Problems with the establishment of rape and wheat in soil with wheat straw residues in the DS system resulted in high losses in individual cases, so that the profit for DS at the midpoint period was at 55 euros ha−1. The expanded use of reduced-tillage practices would therefore improve the profitability of crop production in Northeast Germany. The introduction of DS systems would, however, require the modification of common crop rotations and the employment of an appropriate seeding technology.
This review examines the effect of tillage on microbial habitat space, and the roles of microbes in influencing N-transformation processes within a heterogeneous soil environment. Literature relating tillage to microbial processes is assessed critically focusing on (a) degrees of physical disruption and N-processes, (b) interactions between organisms and the soil pore network, and (c) the role of soil structure in mediating oxygen movement to sites of microbial activity in soil. Spatial heterogeneity is shown to be a key characteristic of soil structure and N-transformation processes, impacting on predator:prey relations, microbial habitable pore space, and the modelling of the soil system with respect to denitrification. The latter area is discussed with respect to the notion of how a functional appraisal of soil structure may be approached theoretically, at the aggregate and soil profile scale.
The extent and persistence of the effect of soil compaction in a system with annual ploughing were investigated in 21 long-term field experiments in Sweden with a total of 259 location-years. Crop yield, soil physical properties and plant establishment were determined. All experiments had two common treatments: control (no extra traffic) and compacted (350 Mg km ha⁻¹ of experimental traffic in the autumn prior to ploughing), using a tractor and trailer with traditional wheel equipment and an axle load restricted to 4 Mg. During the rest of the year, both treatments were conventionally and equally tilled. The compaction was repeated each autumn for at least 7 years, and the yield was determined each year until 5 years after the termination of the compaction treatment.
Long-term tillage and nitrogen (N) management practices can have a profound impact on soil properties and nutrient availability. A great deal of research evaluating tillage and N applications on soil chemical properties has been conducted with continuous corn (Zea Mays L.) throughout the Midwest, but not on continuous grain sorghum (Sorghum bicolor (L.) Moench). The objective of this experiment was to examine the long-term effects of tillage and nitrogen applications on soil physical and chemical properties at different depths after 23 years of continuous sorghum under no-till (NT) and conventional till (CT) (fall chisel-field cultivation prior to planting) systems. Ammonium nitrate (AN), urea, and a slow release form of urea were surface broadcast at rates of 34, 67, and 135 kg N ha−1. Soil samples were taken to a depth of 15 cm and separated into 2.5 cm increments. As a result of lime applied to the soil surface, soil pH in the NT and CT plots decreased with depth, ranging from 6.9 to 5.7 in the NT plots and from 6.5 to 5.9 in the CT plots. Bray-1 extractable P and NH4OAc extractable K was 20 and 49 mg kg−1 higher, respectively, in the surface 2.5 cm of NT compared to CT. Extractable Ca was not greatly influenced by tillage but extractable Mg was higher for CT compared to NT below 2.5 cm. Organic carbon (OC) under NT was significantly higher in the surface 7.5 cm of soil compared to CT. Averaged across N rates, NT had 2.7 Mg ha−1 more C than CT in the surface 7.5 cm of soil. Bulk density (Δb) of the CT was lower at 1.07 g cm−3 while Δb of NT plots was 1.13 g cm−3. This study demonstrated the effect tillage has on the distribution and concentration of certain chemical soil properties.
A better understanding of tillage and stubble management effects on surface soil structure is vital for the development of effective soil conservation practices for the long-term. Relationships between aspects of soil structure and runoff/soil loss were investigated in 24 year old field experiment on an Oxic Paleustalf, in NSW, Australia. Two tillage/stubble management systems were compared, namely direct drilled/stubble retained (DD/SR) versus conventional tillage/stubble burnt (CC/SB). Tillage and stubble burning significantly increased bulk density and decreased the macro-aggregate stability, mean weight diameter (MWD), geometric mean diameter (GMD) and total porosity, particularly macroporosity (>60 μm). For the 0–5 cm layer, DD/SR had significantly higher water stability of macro-aggregates >2 mm than CC/SB (165 g/kg versus 78 g/kg), and the volume of pore space of diameter >60 μm at 0–5 cm depth was significantly greater (more than 11%) for DD/SR than for CC/SB. Under simulated rainfall (100 mm/h) and the removal of surface stubble, both runoff and soil loss were significantly higher under CC/SB compared to DD/SR. The infiltration rate at the end of the experiment under DD/SR was 3.7 times that of CC/SB (85 mm/h versus 23 mm/h). There were significant correlations between the proportion of soil particles >0.25 mm measured after wetting by rain and both final infiltration rate (P < 0.001) and soil loss (P < 0.001). It was concluded that 24 years of direct drilling and stubble retained practices significantly reduced runoff and soil erosion hazards, due to a fundamental change in soil structure, viz. higher soil aggregate stability and higher macroporosity of the surface soil.
This paper reviews research performed at the Justus-Liebig-University of Giessen, Germany into the impact of different tillage systems on soil properties and quality. The impact of intensive soil tillage treatments on several soil properties was described by means of selected data obtained through long-term interdisciplinary research.The experiments were based on comparative application (long-term, up to 18 years investigations) of the respective tillage options on different soils (e.g. Eutric Cambisol, Eutric Fluvisol) ranging in texture from sand to a silt loam. These soils are located at five field sites with different crop rotations in the central German state of Hesse. Tillage intensity of the systems was considered to decrease in the following sequence: Conventional plough tillage (CT), reduced tillage (RT), and no-tillage (NT).For elucidating the impact of tillage intensity, the tillage extremes CT and NT were compared. Physical conditions of soil as influenced by the application of RT were considered to be intermediate between CT and NT. In general, bulk density in the upper layer of NT soils was increased, resulting in a decrease in the amount of coarse pores, and a lower saturated hydraulic conductivity when compared with the CT and RT soils. Surface cover by crop residues and higher aggregate stability under NT protected soil fertility by avoiding surface sealing and erosion. Lateral losses of herbicides were also reduced under NT conditions, whereas the susceptibility for preferential vertical transport of herbicides needs further evaluation. Accumulation of organic matter and nutrients near the soil surface under NT and RT were favorable consequences of not inverting the soil and by maintaining a mulch layer on the surface. Those improvements were associated with enhanced biological activities in NT and RT topsoils. Increased earthworm activity in NT treatments was associated with a system of continuous macropores which improved water infiltration rates. Earthworms support decomposition and incorporation of straw. Soils which have not been tilled for many years were more resistant to vehicle passage; consequently, the compaction by traffic was lower. Penetration resistance curves indicate that a uniformly stable structure had developed over the years in NT soils.Overall, the results show that RT and NT were beneficial to the investigated soil properties. If crop rotation, machinery, and plant protection are well adapted for the introduction of conservation tillage, these systems may replace conventional ploughing systems in many cases in German agriculture.
Soil structure is very important in agriculture since it affects soil and plant root attributes, such as root system distribution, soil water and nutrient transport, and heat transfer. Degraded soil structures may be repaired by wetting and drying cycles due to changes in the soil pore system. Gamma-ray computed tomography (CT) was used as a tool to evaluate the effect of wetting/drying cycles on soil structure repair, using samples collected in aluminum cylinders. A first-generation tomograph with an 241Am source and a 7.62 cm × 7.62 cm NaI(Tl) scintillation crystal detector coupled to a photomultiplier tube were employed. Image analysis and tomographic unit profiles showed that CT can provide an insight into sample structure in order to evaluate repairs and so improves the use of this tool in relation to the judgement of the quality of measured soil physical properties.
Knowledge of soil shrinkage behavior is needed to improve the understanding and prediction of changes of unsaturated hydraulic properties in non-rigid soils. The heterogeneity and interaction of horizontal and vertical soil shrinkages that produce soil cracks and associated soil subsidence require additional quantification. Vertical shrinkage can be calculated easily by soil height with vernier caliper. However, a quantitative and feasible measurement of horizontal shrinkage has not been developed yet because of the complicated and irregular geometry of soil cracks. This paper introduces a new method to measure soil cracks non-destructively and continuously by digital image analysis. Using Adobe Photoshop and Windows Scion 4.02 image processing, the proposed procedure accurately identifies changes as small as 1.0 mm2 and shows differences even when areas of soil cracks were increased by as little as 1%. Various geometry factor values indicated soil shrinkage in the two dimensions was anisotropic during the whole drying. During initial dehydration from saturation, only subsidence shrinkage could be identified. With the further dehydration, the soil cracks developed and increased in size. These results suggest that the heterogeneity of soil shrinkage in 2D should be taken into account when modeling the total soil shrinkage behavior and associated unsaturated hydraulic properties.
Our research was aimed at analysing the possibilities of using a geophysical method, the electrical resistivity method, to describe the structure of a cultivated loamy soil. Soil electrical resistivity was measured in laboratory conditions on two soil blocks (0.30 m × 0.30 m × 0.20 m) with 2D Wenner configuration using an inter-electrode spacing of 0.015 m. The two soil blocs exhibited different structure: one with a compacted structure (bulk density equal to 1.59 Mg m−3 with a standard deviation of 0.05 Mg m−3) and the second with a porous structure (bulk density equal to 1.39 Mg m−3 with a standard deviation of 0.04 Mg m−3). The electrical resistivity results showed a significant 10 Ω m difference between the compacted block (30 Ω m) and the porous block (40 Ω m) due to the difference in their bulk density. This structural distinction by electrical resistivity needs temperature correction using the Campbell equation. The soil electrical resistivity was also measured in the field with a 2D Wenner configuration using an inter-electrode spacing of 0.10 m along a 3.20 m transect. After the electrical measurements, a pit was dug and the contours of porous and compacted zones in the ploughed layer were identified, the boundaries between the ploughed layer, the plough pan and the pedological horizons were defined. Comparisons between inverted electrical resistivity maps and visual morphological descriptions showed the ability of electrical resistivity to detect wheels tracks. However, electrical surveying in a heterogeneous field after ploughing did not correspond to the visual morphological description, the latter being 2D whereas the electrical resistivity map is a 2D projection of a 3D sensing. As a non-destructive method, the electrical resistivity method could improve the quantitative description of the tilled layer and permit a temporal survey.
A simple photogrammetric method developed for three-dimensional mapping of soil surfaces is described. Tilled soil was photographed in stereo with a hand-held 35 mm camera from about 2 m above the ground. A portable frame with 26 control points was used to level and scale the stereomodel. Ground measurements were captured from film enlargements with a standard digitizing tablet and used to generate a digital elevation model (DEM). Ground measurement accuracy was about 2 mm. Despite systematic errors, the method holds promise for soil scientists with limited training in photogrammetry.
Passes of tractors and agricultural machines during the growing season take place not only over the loose soils but also over the untilled soils in the cultivation of perennial plants. The aim of the investigation, carried out at a depth of 0–30 cm on two soils (Orthic Luvisol developed from loess and Calcic Cambisol developed from chalk formations) was to determine the effect of one pass of a C 360 tractor of 2700 kg over the soil in the third year of alfalfa (Medicago varia Martin) cultivation. The soil physical properties, e.g. bulk density, total porosity, air capacity and air permeability and morphological characteristics were evaluated.The passage of a tractor 3 t in weight did not cause any significant changes in the structure or air-water properties of the soils.
Cone resistance is an empirical measure of soil strength that can rapidly identify areas where soil depth or soil compaction may be limiting yields. However, large numbers of measurements would be required to describe and assess spatial variability, quite likely at prohibitive costs. It then needs to apply an interpolation method in order to estimate data in unsampled locations.In this paper, cone resistance measurements were made according to a three-dimensional grid in a 30×90 m2 field cropped to rain-fed durum wheat during crop season. At each sampling date, cone resistance data were interpolated using geostatistical techniques to produce three-dimensional maps. Cone resistance showed random variations on the horizontal surface, while in depth revealed the persistence of a quite shallow compacted zone. Late in the crop season, soil strength increased sensitively, reaching values greater than 2.5 MPa even at the surface.Moreover, to summarise cone resistance profile measurements made at different sites within the field, a particular geostatistical technique, called indicator kriging, was applied. The probability map of exceedence of 2.5 MPa through the rooted soil depth showed two wide areas of high impedance in March 2000.This research has confirmed the persistence of soil structure over time and has proved that geostatistical techniques may be used as a powerful tool in understanding and assessing of spatial variability of soils.
Improper cropping and overgrazing have led to land degradation in semi-arid regions, resulting in desertification. During desertification, vegetation changes have been widely observed, and are likely controlled to some extent by soil water. The purpose of this study was to investigate changes in soil physical properties, organic C, and vegetation induced by land-use changes, with special reference to the dynamics of available soil water. We selected four study sites in a typical Mongolian steppe grassland: grassland protected from grazing, grazed grassland, abandoned cropland, and cultivated cropland. Grazing exclusion increased the cover of perennial grass, with little increase in the root weight. Since there was no difference in available water between the grasslands with and without grazing, there appears to be no serious soil compaction due to overgrazing. On the other hand, vegetation cover and the number of species were poor in both abandoned cropland and cultivated cropland. However, the root weight was greater in abandoned cropland. Although the abandonment of cultivation appeared to increase organic C, available water did not differ significantly in comparison with cultivated cropland. The silt contents were significantly lower in abandoned and cultivated cropland than in both grasslands, suggesting the effects of wind erosion. In addition, the silt contents were positively correlated with the volume fraction of storage pores for available water. Therefore, the lower silt contents may constrain the volume of available water in abandoned cropland. Moreover, the unsaturated hydraulic conductivity results indicated that the diameters of storage pores for available water at the present study sites were smaller than those suggested by previous studies. Although the differences in vegetation cover by different land-use types were observed at every site, differences in the volume of available water were observed at between abandoned cropland and cultivated cropland. The reason why the no differences in available water between grazed grassland and grasslands protected from grazing may be short time of grazing exclusion for 2 years for evaluating the effects of exclusion on soil properties.
Soil organic carbon (SOC) and its different labile fractions are important in minimizing negative environmental impacts and improving soil quality. However, very little is known of the dynamics of SOC and its labile fractions after the cultivated wetlands have been abandoned in northeast China. The objectives of this study were (1) to estimate the dynamics of SOC after the abandonment of cultivated soil, (2) to investigate the most sensitive fraction for detecting changes in organic C due to the abandonment of cultivated soil, and (3) to explore the key factors affecting the dynamics of soil C after the abandonment of cultivated soil in the freshwater marsh region of northeast China. Our results showed that the abandonment of cultivated wetlands resulted in an increase in SOC and the availability of C. The SOC content increased to 31, 44, and 107 g kg−1 after these cultivated wetlands were abandoned for 1, 6, and 13 years, respectively, as compared to an SOC content of 28 g kg−1 in the soil that had been cultivated on for 9 years. In northeast China, where a cultivated wetland was abandoned, the initial regeneration of SOC pools was considerably rapid and in accordance with the Boltzmann equation. An analysis of the stepwise regression indicated that the dynamics of SOC (g kg−1) can be quantitatively described by a linear combination of the root density and the mean soil temperature 5 cm underground in the growing season, as expressed by the following relationship: TOC = 0.008 root density −3.264T + 96.044 (R2 = 0.67, n = 9, p < 0.05. T is the mean soil temperature 5 cm underground in the growing season), indicating that approximately 67% of the variability in SOC can be explained by these two parameters. The root biomass was the key factor affecting SOC concentration according to the observation made during the recovery of cultivated soil that was abandoned. Soil temperature indirectly influenced the SOC concentration by affecting soil microbial activity. The abandonment of cultivated wetlands resulted in an increase in the light-fraction organic C (LF-OC), microbial biomass C (MBC), and dissolved organic C (DOC) concentration. The rate of increase in LF-OC was considerably higher than that in SOC and HF-OC. Similarly, the rate of increase in MBC was also considerably higher than that in SOC in cultivated soils abandoned for 4–8 years. However, the rate of increase in DOC was far lower than that in SOC. The R2 value for the correlation between the increments of the LF-OC and SOC was significantly higher than that for the correlation between DOC and MBC (0.99 vs. 0.90), indicating that LF-OC was the most sensitive fraction for detecting changes in organic C due to the abandonment of cultivated soil.
Three field experiments using tomatoes (summer) and cabbages (winter) were conducted to assess practical means of increasing the absorption of water from furrows into beds of red-brown earth soils having a hardsetting and crusting sandy or fine sandy loam A horizon. Treatments were applied to the irrigation furrows, including cultivation before each irrigation, calcium amendment as surface-applied gypsum or calcium chloride dissolved in irrigation water, added wheat straw or oaten-hay mulch, and a sown-oat mulch. Absorption as a consequence of irrigation was determined on several occasions by measuring gravimetric moisture content a day before and after irrigation in a grid between the plant row and furrow edge. Additional measurements in the first experiment included yield, and in the third experiment advance times for irrigation water in furrows and soil characteristics at the end of the season. Cultivation before irrigation and mulching (wheat straw, oaten-hay or sown-oats) significantly increased absorption over the control, particularly near the furrow. However, the soil was restored to field capacity throughout the grid at only one of the irrigations sampled (the cultivation treatment in the first experiment). The level of water absorption under the cultivation treatment declined with time. More soil moisture was retained between irrigations under straw and hay mulch. In tomatoes, the straw and hay mulch treatments had greater water absorption at the second irrigation sampled than the first, presumably because the mulch became better anchored and retarded water flow more. However, all the mulch treatments became less effective as the mulch broke down. Calcium salt applied to the furrow surface or in the irrigation water did not improve absorption. Irrigation water advance was slowest under hay and quickest in the control.
Cropping practices commonly used in conservation tillage can potentially impact on earthworm abundance and distribution. Management practices associated with conservation tillage farming for cereals such as stubble retention and management, greater utilization of herbicides, and soil acidity amelioration were assessed for their influence on earthworm density, age structure, and species abundance at a total of seven sites on Chromic Luvisols in north-eastern Victoria, Australia. Earthworms were sampled from the surface soil (0.1 m2 × 0.1 m deep) at the end of the cool wet season (August–September) when species tend to concentrate at this soil depth. In three six-year experiments, crop management practices that retained stubble as a surface mulch for successive years supported consistently higher densities of earthworms, followed by retained stubble left standing, burning stubble, and incorporation of stubble. The latter reduced earthworm densities by an average of 53%, compared to the mulched system. This trend was consistent across texturally different soils. Autumn application of post-emergent herbicides for two consecutive years, at double recommended rates, was associated with significant increases in earthworm densities (by 10–124%) the following spring, compared to the recommended rate. Herbicide application had no influence on earthworm species richness. Although the effect of increasing soil pH on earthworm numbers was variable, lowering the pH consistently lowered earthworm densities (by 60%). No clear trend was observed in earthworm population age structure at any of the sites. Overall, reduced soil disturbance and increased inputs of crop residue at the soil surface, although having little effect on diversity of species, are conducive to increasing earthworm populations in conservation tillage cropping practices in north-eastern Victoria.
Soil mite abundance were measured during a 2-year period (1984–1986) in experimental agroecosystems subjected to conventional tillage or no-tillage treatments. The experimental site is a humid, subtropical floodplain located in Clarke County, GA, U.S.A. Soil mite abundances were greater in conventional tillage during 1984–1985, but became greater in no-tillage during 1985–1986. Soil mite build-up in no-tillage coincided with a major drought during the summer of 1986, when both Prostigmata and Oribatei showed large increases in numbers. Although the effects of drought conditions cannot be readily separated from other trends (since droughts are unreplicated and lack controls), higher populations under no-tillage conditions are consistent with the water retention properties of conservation tillage agroecosystems.
Conflicting reports in the literature on the effects of tillage on earthworms are reviewed in the light of their roles in agro-ecosystem functioning. Tillage can change the abundance (by 2–9 times) as well as the composition (diversity) of earthworm populations. The actual impact is dependent on soil factors, climatic conditions and the tillage operations but hitherto this information was seldom provided in research reports. The declines in earthworm population often reported in conventionally tilled soils are associated with undesirable changes in the soil environmental conditions resulting from excessive tillage. Different species of earthworm respond differently to tillage. While the abundance of the deep burrowing species (anecic) tends to decline under tillage, particularly under deep ploughing, endogeic species can actually increase in number especially when there is increased food supply. Under conservation tillage systems, earthworms can potentially play a more important role than under conventional tillage in the functioning of the farming systems because of their abilities to modify the soil physical environment and nutrient cycling. However, adoption of conservation tillage does not automatically result in an optimal earthworm population in terms of abundance and diversity. There are opportunities to introduce more beneficial species to improve the ecological performance of agro-ecosystems. More research is needed to fully understand the ecology of different earthworm species, their interactions and their potential roles in promoting more sustainable farming systems.
We have studied the impact on arthropod populations of conventional tillage and no-tillage systems in maize. Two different corn–weed control programs were assayed: NT, direct drilling of seed genetically modified to tolerate herbicide plus a combination of two pre-emergence and post-emergence herbicides; CT, conventional drilling with an isogenic corn variety plus a pre-emergence herbicide. Management system affected the soil arthropod community, based on major groups. Lower number of arthropods occurred in CT than in NT. Spider and hymenopteran parasitoids, especially those belonging to the families Lycosidae and Diapriidae were the groups that were most clearly affected. The natural field environment seems to favour the presence of Diapriidae. Spiders, in addition to being abundant, behaved in a similar way during both years of each treatment and might therefore be considered as reliable indicator families of the effects of different soil managements on the arthropod population in corn crops. Management system implies alterations on abundance of arthropods populations and natural enemies present in the crop.
In the humid Pampas of Argentina soybean is cultivated in different soil types, which were changed from conventional- to zero tillage systems in the last decade. Little is known about the response of soybean roots to these different soil physical environments. Pasture, and conventionally- and zero-tilled field lots cropped to soybean (R1 and R2 ontogenic stages) were sampled in February–March 2001 in a sandy clay loam and two silty clay loam Mollisols, and in a clayey Vertisol. In the 0–0.05 m layer of conventionally- and zero-tilled lots soil organic carbon represented 53–72% of that in pasture lots, and showed an incipient recovery after 4–11 years of continuous zero tillage. Soil aggregate stability was 10.1–46.8% lower in conventionally-tilled than in pasture lots, and recovered completely in zero-tilled lots. Soil relative compaction ranged 60.8–83.6%, which was below the threshold limit for crop yields (>90%). In change, soil porosity >50 μm ranged 0.91–5.09% soil volume, well below the minimum critical limit for root aeration and elongation (>10%, v/v). The threshold of soil resistance (about 2–3 MPa) was only over passed in an induced plough pan in the conventionally-tilled Bragado soil (5.9 MPa), and in the conventionally- and zero-tilled Ramallo soils (3.7–4.2 MPa, respectively). However, neither the low macroporosity nor the high soil resistances impeded soybean roots growth in any site. According to a fitted polynomial function, root abundance was negatively related to clay content in the subsoil (R2 = 0.84, P < 0.001). Soybean roots were only abundant in the subsoil of the sandy clay loam Mollisol, which had <350 g kg−1 clay. Results show that subsoil properties, and not tillage systems, were the primary effect of root growth of soybean.
Soil erosion can adversely influence soil quality, especially in tropical soils. Thus, a multi-location field experiment was conducted on eight major agricultural soils with different degrees of erosion, in three eco-regions in Tanzania. The objective was to assess the impact of topsoil depth (TSD) and management on soil properties. Three eco-regions comprising of humid at Kilimanjaro, sub-humid at Tanga and sub-humid/semi-arid at Morogoro were selected. There were a total of eight locations within three eco-regions comprising two at Kilimanjaro (e.g., Kirima Boro and Xeno Helena), two at Tanga (Mlingano 1 and Mlingano 2) and four at Morogoro (Misufini 1, Misufini 2, Misufini 3, and Mindu). The soil management treatments consisted of farmyard manure (FYM), N and P fertilizer, tie-ridging and farmers’ practice. Plant nutrient content was generally lowest on severely eroded and the highest on least eroded soil classes. Soil pH decreased with increasing severity of erosion on soils with higher content of Ca+2 in the sub-surface. In general, there occurred a decline in soil organic carbon (SOC) and P with the decrease in TSD. The SOC content decreased on severely eroded soil class by 0.16%, 0.39% and 0.13% at Misufini 1, Mlingano 1 and Kirima Boro, respectively, compared to slightly or least eroded soil class. Corresponding decline in available P at these sites was 41%, 62% and 61%, respectively. Application of FYM significantly increased soil pH at some sites. Soil content of SOC, N, P, K and Mg were significantly increased by FYM application. Significant effects of N and P fertilizers on SOC and P were observed at most sites. In comparison with farmer’s practice, FYM application increased SOC by 0.55%, N by 0.03%, P by six-fold and K by two-fold. Nitrogen and phosphorus fertilizers had comparable effects for SOC and P only at some sites. The results indicate that FYM is a better soil input than N and P fertilizers in improving soil quality. The data show that SOC, N and P are most adversely affected with accelerated erosion and that FYM fertilizer applications have the potential to improve fertility of eroded soils.
Reliable recommendations for practice are required, to enable farmers themselves to decide whether or not it is acceptable to drive over the soil under the prevailing conditions. To this end, the pressure propagation has to be calculated by means of easily recorded parameters. The TASC program (Tyres/Track And Soil Compaction) makes a contribution to this.The risk of soil compaction may be evaluated with reference to six parameters (tyre size, wheel load, tyre inflation pressure, topsoil stability, soil type and maximum tillage depth).The program uses these parameters to evaluate the soil stress caused by tyres and tracks.The aim of the study is on the basis of field measurements to derive a regression equation for calculation of the q value (as a measurement of soil hardness when calculating the pressure propagation in the soil) as a function of the penetration resistance. The topsoil stability can then be taken into account when calculating the compressive stress. Locations ranging from high (ley on dry clay soil) to very low soil stability (shortly after ploughing) were selected for the purpose of the study. Soil pressure measurements were made at plough pan level at a total of nine sites (cropland and pasture) with light to heavy soils. Different machine weights were used, producing wheel loads varying from the empty slurry tanker (wheel load 1432 daN) to the 6-row sugar beet harvester (wheel load 10,678 daN).The q value is a measure of topsoil stability (penetration resistance). The q value is determined by the compressive stress at a particular depth, by the depth itself, by the contact area and by the wheel load. The so-called equivalent contact pressure can be recalculated on the basis of the compressive stress values measured at a depth of 20 cm. The ratio of the equivalent contact area pressure to the measured contact area pressure (wheel load/measured contact area) gives the q value. This value increases as the soil stability decreases.For the purpose of the regression calculation a logarithmic function was derived for mineral soils from the upper quartiles on the one hand and from the medians of the q value and the medians of the penetration resistance on the other.The coefficient of determination is 0.71. The function applies to mineral soils. First measurements on organic soils indicate that mineral and organic soils react differently to pressure propagation.No direct correlation was found here between penetration resistance and soil moisture.
Hedges are part of the landscape in many regions of the world. Among many important roles, they limit soil translocation. Hedges perpendicular to the slope at the lower end of sloping fields result in the formation of soil terraces. Quantification of fluxes of matter at the landscape scale has shown that terraces cannot be neglected. In this study, we try to quantify and explain the origin of the morphological and geochemical properties of terraces. The morphology of the terraces and corresponding stocks of soil material and chemical elements are assessed through a microtopographic study. The 11-ha study area is located on a rolling landscape in the Massif Central (France). The study is focused on three particular terraces. Two DEMs (2.5-m resolution) were established on the study area. The first DEM (DEM1) represents the actual elevation, using 4600 elevation spots. Elevation cross-sections were computed to determine the extent of the terraces, and a second DEM (DEM2) was then calculated, excluding all the elevation spots located in terraced areas. The thickness of soil material stored in each terrace is given by DEMst = DEM1 − DEM2. It varies between 0 and 0.63 m, representing a soil accumulation of 3–7 m3 m−1 hedge length. One-hundred and seventy-three samples were taken in the topsoil, and the content in some major and trace elements (Ca, Mg, K, Fe, Mn, Cr and Co) measured and mapped using ordinary kriging. The stock of these elements accumulated in the terraces was computed and compared to the stock eroded considering uniform erosion from the upper part of the fields. Results show a difference in stocks exceeding more than 20% for several elements, showing that uniform erosion is not a satisfactory explanation for the accumulations observed in the terraces. A higher contribution of the area located immediately upslope form the terraces results in a better agreement in the stocks comparison for most of the chemical elements studied. Evidence from coarse fragments study, particle size distribution, soil depth in the upslope part of the fields and microtopography show that the formation of the terraces is probably mainly due to redistributions through tillage. The geochemical properties of the terraces are probably exclusively the result of this mechanical redistribution, except for Mn and Co. Indeed, it is likely that since the plantation of the hedges, seasonal waterlogging conditions have significantly affected the mobility of these two elements through geochemical processes that resulted in their leaching downwards as well as perhaps out of the field.
The effects of tillage frequency (conventional, reduced and zero), primary tillage implement (disc, blade and chisel plough), stubble management (retention and removal), gypsum application and paraplowing were examined with respect to soil water storage, soil nitrate accumulation, seedling establishment, crop growth, yield and grain protein content for four successive years of wheat, grown on a sodic, duplex soil in South West Queensland, Australia.Stubble retention generally resulted in more soil water at sowing but less at harvest, compared with stubble removal. This led to higher grain yields in dry growing seasons and has implications for reducing runoff.Zero tillage with stubble removal had the lowest mean water storage and, in dry growing seasons, the lowest grain yield. This indicates that when stubble is absent or lacking, some tillage is needed, probably to break surface seals and increase surface roughness.Zero tillage with stubble retention accumulated the most soil water but the least soil nitrate. Consequently this treatment outyielded all others in the driest growing season but was outyielded by almost all others in the wettest.Increased frequency and aggressiveness of tillage, and stubble removal, increased the amount of soil NO3-N at 0–60 cm. There were no significant (P<0.05) tillage×stubble interactions. In the wettest growing season, wheat grain yields reflected the different levels of NO3-N in the soil. In the other three years, grain protein contents reflected these levels.Both zero tillage and stubble retention reduced the efficiency of water use, probably because both also reduced nitrogen supply. So despite high yields from zero tillage with stubble retention in the dry growing seasons, the full yield potential of this treatment with respect toits water supply was not realized.Gypsum application at 5 t ha−1 had no commercially useful effect on establishment or grain yield and is not recommended. Similarly, paraplowing had no effect on yield. Reduced or zero tillage is recommended, provided that stubble is present and nitrogen supply is adequate.
Conservation management systems can improve soil organic matter stocks and contribute to atmospheric C mitigation. This study was carried out in a 18-year long-term experiment conducted on a subtropical Acrisol in Southern Brazil to assess the potential of tillage systems [conventional tillage (CT) and no-till (NT)], cropping systems [oat/maize (O/M), vetch/maize (V/M) and oat + vetch/maize + cowpea (OV/MC)] and N fertilization [0 kg N ha−1 year−1 (0 N) and 180 kg N ha−1 year−1 (180 N)] for mitigating atmospheric C. For that, the soil organic carbon (SOC) accumulation and the C equivalent (CE) costs of the investigated management systems were taken into account in comparison to the CT O/M 0 N used as reference system. No-till is known to produce a less oxidative environment than CT and resulted in SOC accumulation, mainly in the 0–5 cm soil layer, at rates related to the addition of crop residues, which were increased by legume cover crops and N fertilization. Considering the reference treatment, the SOC accumulation rates in the 0–20 cm layer varied from 0.09 to 0.34 Mg ha−1 year−1 in CT and from 0.19 to 0.65 Mg ha−1 year−1 in NT. However, the SOC accumulation rates peaked during the first years (5th to 9th) after the adoption of the management practices and decreased exponentially over time, indicating that conservation soil management was a short-term strategy for atmospheric C mitigation. On the other hand, when the CE costs of tillage operations were taken into account, the benefits of NT to C mitigation compared to CT were enhanced. When CE costs related to N-based fertilizers were taken into account, the increases in SOC accumulation due to N did not necessarily improve atmospheric C mitigation, although this does not diminish the agricultural and economic importance of inorganic N fertilization.
Conservation tillage is an accepted method of decreasing soil erosion. However, limited information is available concerning N fertilizer requirements of grain sorghum (Sorghum bicolor L. Moench) grown under reduced-tillage management. Tillage effects on sorghum yield and N accumulation in 1985 and 1986 were studied on a Weswood soil (Fluventic Ustochrept) near College Station, Texas (Latitude 30° 35′ N, Longitude 96° 21′ W). Four N rates (0, 50, 100 and 150 kg N ha−1) were applied to plots managed with no-tillage or conventional tillage. Response of grain yield to N rate was curvilinear while that of stover yield was linear. However, tillage and N interactions also influenced grain and stover yield. At low N rates, conventional tillage produced more stover and grain, but at higher rates tillage differences did not occur. Both tillage systems attained maximum grain yield at 122 kg N ha−1 as determined by regression analysis. Nitrogen accumulation in both stover and panicles was linear with N rate. Lower whole-plant N accumulation with no-tillage at low N rates supported the contention that N was less available in no-tillage soils. Leaf N concentration at anthesis was higher in conventional-tillage treatments. However, a regression of leaf N concentration on N rate predicted a maximum leaf N concentration of 34 g N kg−1 at 164 kg N ha−1 for both tillage treatments. When grain yield was regressed on leaf N concentration for each tillage treatment, maximum yield occurred at leaf N concentrations of 32 and 37 g kg−1 for conventional tillage and no-tillage, respectively. Leaf area index measured at anthesis significantly increased with N rate and was greater in conventional tillage. Leaf N concentration and leaf area index were positively correlated with grain yield. Data from this study suggest that fertilizer N amendments to no-tillage sorghum in excess of that required for maximum conventional-tillage yields are not necessary.
Shallow tillage was assessed over a 4-year period for low-input production of spring cereals in Prince Edward Island. The soil was a Charlottetown fine sandy loam, an Orthic Podzol, which is marginally suitable for direct drilling. The tillage systems consisted of mouldboard ploughing, shallow tillage (rotary harrow, disc harrow) to the 10 cm soil depth, and direct-drilling.Plant populations were similar between tillage systems. Shallow tillage and direct-drilling produced similar grain yields as mouldboard ploughing when environmental conditions were optimum, but wet or very dry growing seasons favoured mouldboard ploughing and direct-drilling, respectively. Rotary harrowing prevented reduced plant growth rates prior to tillering and subsequently reduced accumulation of N in the plant and grain, associated with direct-drilling. Generally, the ability of plants to utilize N for growth was considered to be the main factor influencing N yield differences between tillage systems.In comparison to mouldboard ploughing, shallow tillage reduced machinery costs and energy requirements by 25–48% for seedbed production. In addition, shallow tillage had the advantage of timeliness and increased the potential area which could be prepared for seeding during the limited early spring period. Overall, shallow tillage removed some of the constraints associated with direct-drilling and provides an alternative, in rotational farming systems on fine sandy loams, to mouldboard ploughing.
Many biological processes vary in a curvilinear manner, reaching a maximum rate at an optimum water content. Optimum conditions commonly extend across a range in water contents, and providing there are no soil-related limitations to biological processes, this range can be referred to as the non-limiting water range (NLWR) of a soil. The rate of a biological process would be expected to be similar in soils with different structure when the water content is in the NLWR and soils are under similar environmental conditions. This range potentially is a useful characteristic to describe the quality of soil structures with respect to a biological process—the larger the range the higher the quality. The distinction between optimum and NLWR has received little attention. The objective of this study was to determine if gas exchange rates, biomass accumulation in shoots and roots, root morphology and rate of development of maize (Zea mays L.) vary among soils under optimum soil water contents. Plants were grown to the 12-leaf stage under controlled environment conditions in four soils of different texture, packed to two levels of compaction with two rates of N addition and maintained at three different water contents. The optimum water content, for processes involving both shoots and roots, bracketed an air content of 0.15 for the different soils. The magnitude of the plant responses at optimum water content varied among soils and with relative compaction. Plant responses were largest in the Conestogo (loam soil) and smallest in soils with the highest clay contents. The magnitude of several responses decreased with increasing compaction. In the process of determining the NLWR, it is not appropriate to assume that either shoot or root characteristics are similar in soils of different structure when the water content of each soil is within a range that is optimum for that soil. The largest root and shoot growth that can be achieved at optimum water content across a range of soil conditions must be determined and NLWR determined on soils exhibiting these growth rates. Soils at their optimum water content with root and shoot growth that are less than the largest values imply the existence of soil-related limitations and therefore, by definition, have a value of zero for NLWR.