No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
No-tillage drill and planter design-small-scale machines
... They offer versatile use and can be adapted as cultivators, planters, weeders, rotavators or attached to a trailer and sued to transport agricultural produce (figure 7.11). Figure 7.11 Accessories used with power tillers (Source: Ribeiro et al, 2006) 7.5 Advantages of conservation tillage Labour saving: The substitution of conventional tillage by conservation agriculture allows a more even distribution of labour over the year, because of the elimination of ploughing and harrowing activities and the use of cover crops and herbicides. ...
... 8 (a) Tined openers for animal-drawn no-till planters (source:Ribeiro et al, 2006) (b) Animal-drawn planter with fertilizer hopper (photo by BancyMati) ...
This Training Manual summarizes the major components of water conservation techniques practiced in rainfed smallholder agriculture. It focuses more on soil moisture retention and soil fertility management. It covers four specific technologies adaptable by smallholder farmers. These are; crop husbandry, vegetative barriers, cover crops, mulches, soil nutrient management, conservation tillage and agroforestry. For each intervention, the salient characteristics of the technology are described, as well as the design, management and maintenance.
... They offer versatile use and can be adapted as cultivators, planters, weeders, rotavators or attached to a trailer and sued to transport agricultural produce (figure 7.11). Figure 7.11 Accessories used with power tillers (Source: Ribeiro et al, 2006) 7.5 Advantages of conservation tillage Labour saving: The substitution of conventional tillage by conservation agriculture allows a more even distribution of labour over the year, because of the elimination of ploughing and harrowing activities and the use of cover crops and herbicides. ...
... 8 (a) Tined openers for animal-drawn no-till planters (source:Ribeiro et al, 2006) (b) Animal-drawn planter with fertilizer hopper (photo by BancyMati) ...
This Training Manual summarizes the major components of water conservation techniques practiced
in rainfed smallholder agriculture. It focuses more on soil moisture retention and soil fertility
management. It covers four specific technologies adaptable by smallholder farmers. These are; crop husbandry, vegetative barriers, cover crops, mulches, soil nutrient
management, conservation tillage and agroforestry. For each intervention, the salient characteristics of the technology are described, as well as the design, management and maintenance.
... The 'Grasshopper ' no-till seed drill design is similar to earlier small-scale prototypes developed in the 1980s by Massey University agricultural engineering researchers for trials in Pakistan and Philippines. The earlier 1980s small-scale no-till prototypes were designed to be drawn by water buffalo or fitted to walk-behind hand tractors (Ribeiro et al. 2006). ...
... Chisel point tines are suitable in low-residue cover situations. Although development of no-till planting machinery is constantly producing improvements and refinements (e.g., the 'Baker boot' inverted-T shaped opener [10]) the designs specifically for low-cost machines aimed at smallholder farmers are generally kept as simple as possible [11]. Manually operated jab planters are suitable for very small holdings and are available with both seed and fertilizer metering. ...
Conservation agriculture (CA) is an increasingly adopted production system to meet the goals of sustainable crop production intensification in feeding a growing world population whilst conserving natural resources. Mechanization (especially power units, seeders, rippers and sprayers) is a key input for CA and smallholder farmers often have difficulties in making the necessary investments. Donors may be able to provide mechanization inputs in the short term, but this is not a sustainable solution as a machinery input supply chain needs to be built up to continue availability after external interventions cease. Local manufacture should be supported, as was the case in Brazil, but this is a slow development process, especially in sub-Saharan Africa. A more immediate solution is to equip and train CA service provision entrepreneurs. With the right equipment, selected for the needs of their local clientele, and the right technical and business management training, such entrepreneurs can make a livelihood by supplying high quality CA and other mechanization services on a fully costed basis. Elements of the required training, based on extensive field experience, are provided. To catalyse the growth of CA providers’ business, the market can be stimulated for an initial period by issuing e-vouchers for services and inputs.
This Training Manual summarizes the major structural soil and water conservation technologies and practices especially for cropland protection. It covers four specific technologies adaptable by smallholder farmers. These are diversion ditches, terracing, artificial waterways and gully control. For each technology, the salient characteristics of the technology are described, as well as the planning, design, construction, management operation and maintenance. This manual is meant to improve the skills of engineers, technicians, extension workers, managers and practitioners engaged in soil and water management, especially those working in smallholder agriculture in Africa. It is meant to inform, educate, enhance knowledge and practice targeting smallholder agricultural livelihoods.
A field experiment was carried out during the agricultural season (2012-2013) in Moderate Rainfall Area-MRA /Nineveh governorate. Italian Gaspardo Sc250 Seeder modified to ZT farming system used in the cultivation of bread wheat. The experiment included three factors: the first factor was Press wheels with two levels, gang press wheel and mutual press wheel, the second factor was the Opener types with two levels, Hoe (Tine) Opener and inverted (T) Opener, the third one was the seeding depths with two levels (3-4 cm) and (4.1-5 cm). This experiment was implemented with split split plot under randomized complete block design with three replicates where the press wheels represented the main plot while the Openers within subplot and seeding depths were under sub sub plot. The mechanization Traits studied were: (slippage percentage, fuel consumption, field efficiency, power requirements).The results showed a significant effect of gang press wheel in enhanced these mechanization traits: (slippage percentage, fuel consumption, field efficiency, power requirements) compared with mutual press wheel. The results also indicated the less significant value of the Hoe opener. The results again showed the significant effect of (3-4 cm) seeding depth in improving the fallowing traits: (slippage percentage, fuel consumption, field efficiency, power requirements) compared with the depth (4.1-5 cm). The interaction between the two types of press wheels and opener types had a significant effect in mechanization traits. The interaction between gang press wheel with seeding depth (3-4 & 4.1-5 cm) had a significant effect in enhancing mechanical characteristics (Slippage percentage, Fuel consumption, Field efficiency, Power requirement). The dual interaction between the Hoe tine with seeding depth (3-4 cm) recorded the best results for the following traits (Slippage percentage, Fuel consumption, Power requirements) and high field efficiency compared with other treatments. Triple interaction between gang press wheel with Hoe tine and seeding depth (3-4 cm) had best values for the studied traits (Slippage percentage, Fuel consumption, Field efficiency, Power requirements) compared with other treatments.
The Nepalese government's policies concerning mechanisation of agriculture generally warn that it could lead to large rural unemployment and therefore only labour intensive technologies should be promoted. This policy has led to only a few mechanisation projects in the public sector while the fairly active private sector moves forward in introducing whatever technologies they felt were marketable. This has resulted, writes in Nepal following a "western" pattern of mechanisation that looks more like that of the Punjab rather than the "AT" pattern of Bangladesh.
Greenhouse gas emissions from soil depend on land use, cropping systems, and tillage methods. The impact of 30 years of continuous corn (Zea mays L.) with moldboard plow tillage was evaluated from four treatments and a control: silage removal versus grain removal, each with low [83 kg N ha-1 (74 lb N ac-1)] and high [166 kg N ha-1 (148 lb N ac-1)] fertility, and no added fertilizer with grain removal. Soil organic carbon (SOC) changes over a 30-yr period were measured, as well as tillage-induced CO2 loss immediately after moldboard plowing, in the spring of 1996. The 24 h cumulative tillage-induced CO2 loss was not significantly different among treatments (excluding the control). Total C, total N, and C:N ratio in the soil remained virtually unchanged after 30 yr in fertilized treatments. All four treatments produced the same SOC content [21.9 g kg-1 (2.2%)] in the 0·20 cm (0·8 in) depth. The cumulative total input of 241 Mg ha-1 (107 t ac-1) of aboveground stover from the high fertility grain treatment, compared to none from the high fertility silage treatment, yielded no differences in SOC. Fertilizer N rates of 83 and 166 kg ha-1 (74 and 148 lb ac-1) produced no difference in SOC or associated C:N ratios. Moldboard plow tillage caused rapid soil degassing that masked fertilizer and stover removal and/or return effects on SOC. This uncontrolled SOC decline agreed with other studies in this region, indicating that the soils were sources of CO2 regardless of other agronomic practices, as long as moldboard plow tillage was used.
Soil organic carbon (SOC) makes up about two-thirds of the C pool in the terrestrial biosphere; annual C deposition and decomposition to release carbon dioxide (CO2) into the atmospheric constitutes about 4% of this SOC pool. Cropland is an important, highly managed component of the biosphere. Among the many managed components of cropland are the production of crop residue, use of tillage systems to control crop residue placement/disturbance, and residue decomposition. An accumulation of SOC is a C sink (a net gain from atmospheric CO2) whereas a net loss of SOC is a C source to atmospheric CO2. A simple three components model was developed to determine whether or not conservation tillage systems were changing cropland from a C source to a C sink. Grain/oil seed yields and harvest indices have indicated a steadily increasing supply of crop residue since 1940, and long term field experiments indicate SOC storage in no-tillage > non moldboard tillage > moldboard tillage systems. According to adoption surveys, moldboard tillage dominated until about 1970, but non moldboard systems are now used nationally on at least 92% of planted wheat, corn, soybean, and sorghum. Consequently, since about 1980, cropland agriculture has become a C sink. Moldboard plow systems had prevented a C sink response to increases in crop residue production that had occurred between 1940 and 1970. The model has not only facilitated a qualitative conclusion about SOC but it has also been used to project production, as well as soil and water conservation benefits, when a C credit or payment to farmers is associated with the C sink in cropland agriculture.
Frozen soil is a major cause of runoff and erosion on many watersheds. Tillage and crop residue management greatly affect soil freezing but their effects have been nearly impossible to predict. A detailed, physically-based model is presented which integrates detailed representations for the interrelated heat, water and solute transfer through snow, crop residue and soil. Measured or estimated hourly weather data are used to predict soil freezing depths, evaporation and profiles of temperature, moisture, ice and solutes.
A Simultaneous Heat And Water (SHAW) model to provide this predictability by simulating the interrelated heat, water and solute transfer through snow, crop residue and soil was presented in a companion paper. Detailed climatic, soil temperature, water content and frost depth data were collected for six diverse tillage-residue conditions during two winters to verify the model predictions. When compared to measured values, simulated soil temperatures were excellent, simulated frost depths were quite good, and simulated soil water profiles were good. Minimal calibration was necessary because the model uses fundamental equations for heat and water transfer with readily definable site parameters.
A single sequence of conventional tillage operations, consisting of mouldboard plough, tandem disc (double pass) and C-tine cultivator, translocated 90 kg soil m-1 slope width when tillage was conducted upslope, and 142 kg m-1 when conducted downslope. Net downslope translocation resulting from one upslope tillage sequence and one downslope, was 52 kg m-1. Assuming one sequence of tillage operations occurs per yr and is conducted upslope and downslope equally often, the rate of net downslope translocation would be 26 kg m-1 yr-1. The estimated rate of soil loss from this area was in excess of 5.4 kg m-2 yr-1 (54 t ha-1 yr-1). Tillage erosion accounted for at least 70% of the total soil loss from natural and tillage erosion as estimated by resident 137Cs. -from Authors
The potential to mitigate greenhouse gas emissions and global climate change is one factor driving agricultural policy development of programs that might pay farmers for practices with a high potential to sequester carbon. With chapters by economists, policy makers, farmers, land managers, energy company representatives, and soil scientists, Agricultural Practices and Policies for Carbon Sequestration in Soil explores a broad range of topics. It examines topics such as the effects of soil tillage and mulch rate, soil monitoring and assessment, soil fertility management, policy options, and the economic issues associated with carbon sequestration. This volume caps a "series" of books from leading researchers on carbon sequestration in soils by integrating the science with the economic and policy issues surrounding it. It provides agricultural scientists, farmers, and policy makers with innovative and environmentally friendly practices for improved land management and crop production. Agricultural Practices and Policies for Carbon Sequestration in Soil helps to identify strategies that can lead to widespread adoption of management practices that will enhance productivity, the soil carbon pool, and the overall environment.
Rice-wheat is the major cereal cropping system in Bangladesh and the eastern Gangetic Plains of India; however, due to the lateness of the monsoon rice harvest and the traditional tillage operations, sowing of wheat is often quite late, reducing the potential for wheat yields by 1.3% per day sown late. Many alternative tillage options have been tested in Bangladesh by participatory methods with growers, agricultural engineers, economists and agronomists. These include:
Power operated tiller cum seeder behind the Bangladesh Hand Tractor (BHT): There are more than 600,000 BHTs in Bangladesh, and the use of this accessory that prepares a shallow but effective seedbed (~5 cm deep) and sows the wheat in a line and presses the seed in the soil in one pass is very effective.
Surface Seeding
Minimum tillage
All methodologies, experiments, and research findings with economic analyses will be discussed in detail.
A number of techniques are described which sought to characterise the physical effects of coulter passage on the soil beneath and to the side of direct-drilled grooves. Measurements were made of the instantaneous and permanent soil deflection and of the zone of influence of individual coulters. No single measurement was considered to be wholly representative but collectively, data obtained from pressure sensing, bulk density, and penetrometer instruments agreed well. These were also supported by photography and electron-microscopy.
An experimental hydraulic downpressure system was designed and tested on a no-tillage grain drill. Regulated downpressure to individual row units provided centralized downpressure adjustment and unit flotation for improved uniformity of planting depth. The system performed adequately in several years of field use. Passage of the drill over simulated soil undulations produced hydraulic pressure surges which were significantly affected by transmittal distance, field speed, and system pressure. An air damping system reduced the magnitude of the pressure surges for more uniform planting depth. The system could be used to convert existing planters and drills for use in no-tillage conditions.
Drilling, band sowing, broadcast sowing, and precision drilling are dealt with. The uniformity of the sowing depth is described by its standard deviation. It is shown that the field emergence of small grains under average German conditions can be improved distinctly by seeding methods with a small standard deviation of the mean seeding depth. The seed distribution over an area is compared by using the mean distance to the nearest neighboring kernel with a fixed seed rate. This measure takes into account the seed distances in all directions. The evaluation shows that the best seed distribution over an area with bulk-metering methods is obtained by broadcast sowing. However, the result with broadcast sowing can be surpassed by precision drilling provided a small row-spacing is used. The effect of the seed distribution over an area on the yield is considered. Improving the seed distribution over the area with small grains, rape, or field beans results in moderate yield increases.
Ploughing is expensive in energy, particularly as speed increases. Direct drilling is quicker, uses less energy and costs less, both in capital and operating costs. Results with a specially-constructed test rig pointed to the need for a heavy drill and to the superiority of triple-disc coulters to other systems, except on stony soils. Some commercially available machines of various types are described.
Laboratory studies were conducted to characterize the adsorption-desorption and degradation of thiobencarb in soil. Thiobencarb adsorption on soil was correlated with soil organic carbon (r = 0.97) and values (ml g ⁻¹ ) for the following soils were: Pahokee muck 339, Everglades muck 169, and Immokalee sand 14. The adsorption values (ml g ⁻¹ ) per unit of organic carbon were Immokalee sand 1195, Pahokee muck 765, and Everglades muck 539. In desorption studies, thiobencarb K f values increased 80 ml g ⁻¹ from the first to the third desorption step in the muck soils, but were similar in three desorptions from the sand. The half-lives of thiobencarb averaged 16, 18, and 24 days on surface samples of Pahokee muck, Everglades muck, and Immokalee sand, respectively, across the range of 25 to 35 C and 10 to 100 kPa soil water tension. Half-lives were generally longer with water contents equivalent to 100 kPa than 10 kPa soil water tension and incubated at 25 than 35 C. The relative percentages of extractable ¹⁴ C, bound ¹⁴ C, and ¹⁴ CO 2 from ¹⁴ C-thiobencarb-treated soil were dependent on soil type, soil water content, incubation temperature, and time.
Agricultural carbon (C) sequestration may be one of the most cost effective ways to slow processes of global warming. Numerous environmental benefits may result from agricultural activities that sequester soil C and contribute to environmental security. As part of no-regret strategies, practices that sequester soil C help reduce soil erosion and improve water quality and are consistent with more sustainable and less chemically dependent agriculture. While we learn more about soil C storage and its central role in direct environmental benefits, we must understand the secondary environmental benefits and what they mean to production agriculture. Increasing soil C storage can increase infiltration, increase fertility and nutrient cycling, decrease wind and water erosion, minimize compaction, enhance water quality, decrease C emissions, impede pesticide movement and generally enhance environmental quality. The sum of each individual benefit adds to a total package with major significance on a global scale. Incorporating C storage in conservation planning demonstrates concern for our global resources and presents a positive role for soil C that will have a major impact on our future quality of life.
An experimental approach was developed in order to study the determinism of superficial structural evolution under rainfall effect. Elementary mechanisms of aggregate breakdown were investigated, analysing the behaviour of different silty soils during immersion under water or wetting by capillarity. A model of superficial structural evolution and crusting is proposed. It is based on the interactions between the initial state, the rainfall characteristics and the soils properties. The aim of this model is to predict the crust formation in relation with the pedologic and climatic characteristics. It can be used like a sub-model of a general model of runoff and erosion. -from Author
Long-term data shows the effect of intensive tillage on soil carbon loss and suggests the need for alternative management strategies. Conservation agriculture with improved tillage methods can aid in carbon sequestration. This work demonstrated that secondary tillage methods decreased the CO2 loss immediately following the moldboard plow. Both the disk harrow and the field cultivator reduced the CO2 flux immediately following the moldboard plow operation by 40 to 50 %. Major soil reconsolidation with one pass of a road packer caused an abrupt decrease in the CO2 flux after primary tillage by moldboard plow, chisel plow, subsoiler, and paraplow. Further small decreases in CO2 fluxes were noted with four passes of the packer. The abrupt decreases in gas exchange were related to increases in soil bulk density following the compaction. These results demonstrate the importance of soil physical properties before and after tillage controlling gas fluxes and soil carbon loss.
For the last 50 years, the consensus view among researchers has been that organic matter (OM) has little or no effect on the available water capacity (AWC) of soil. The historical development of this viewpoint is traced, and it is argued that the literature on this subject has been misconstrued. In addition to a critical review of the literature, published data were evaluated to access the effect of OM content on the AWC of surface soil. In all texture groups, as OM content increased from 0.5 to 3%, AWC of the soil more than doubled. Soil OM is an important determinant of AWC because, on a volume basis, it is a significant soil component. -from Author
The technique is based on the principle that seeds coated with a heavy metal powder (red lead oxide, Pb 3O 4) and X-rayed appear on an X-ray radiograph as white or gray spots on a dark background in the soil. Solder wires placed on the soil sample as reference markers appeared on the radiograph as white lines. Images on the radiograph were shadow representations of true locations in the sample. Thus, a correction procedure was developed based on the geometry of the X-ray equipment to establish the correct position of each image. These corrected seed and reference positions were then used to calculate sowing depth, in-row spacing and width of spread in the row.
Two new prototype conservation seeders and an end-wheel seeder were evaluated in the Pacific Northwest dryland production area for seeding edible green peas. Field tests were conducted in 1989 and 1990 on plots with no tillage or fall chisel plowing plus secondary field cultivations prior to seeding. A strip-till seeder and cross-slot seeder showed good potential for spring seeding peas into chisel plowed and untilled wheat stubble. The end-wheel seeder performed well in tilled plots. There were no significant differences in the amount of soil water lost between seeding and emergence for the three seeders. Regardless of the seeder or prior tillage, when seeds were placed in contact with soil that had between 50 and 150 kPa (0.5 and 1.5 bars) water tension, over 85% of the seeds emerged and established plants.
Society's desire to sequester C in soils, thereby reducing the net loss of CO2 (a greenhouse gas) to the atmosphere, is well known. It is also accepted that the choice of appropriate agricultural management practices adopted by producers will affect this goal. However, quantification of the extent and rate at which it can be achieved is uncertain. A crop rotation experiment that was initiated in 1957 on a thin Black chernozemic clay soil at Indian Head, Saskatchewan, was managed using conventional tillage until changed to zero tillage in 1990. Soil was sampled (0- to 7.5- and 7.5- to 15-cm depths) in May 1987 and 1997 to determine the effects of treatments on soil organic C (SOC) and total N. The rotations were: fallow-wheat (Triticum aestivum L.) (F-W), F-W-W, continuous wheat (Cont W), legume green manure (GM)-W-W, and F-W-W-hay (legume-grass)-hay-hay (F-W-W-H-H-H). The monoculture cereal rotations were either fertilized with N and P based on soil tests or unfertilized, while the legume systems were both unfertilized. There was also a F-W-W (N+P) treatment in which the straw was baled and removed. When the experiment was changed to zero tillage management in 1990, the fertilizer protocol was changed to satisfy the "moist soil" criteria. Consequently, higher rates of N and P were added thereafter to the fallow crop, resulting in a positive yield response of wheat grown on fallow, where before there was no response to fertilizer. Over the 10-yr period (1987-1997) fertilized soil gained C and N, but unfertilized soil did not. For example fertilized F-W, F-W-W and Cont W gained about 4, 5 and 2 Mg C ha-1 in the 10-yr period. During this period, C emissions from manufacture and transportation of N fertilizer was 0.28, 0.53 and 0.90. Mg ha-1 for these three rotations, respectively. These results suggest that without adequate fertility, conversion to zero tillage may not always result in an increase in soil C or N. By 1997, fertilizer increased soil C and N in F-W-W and Cont W, and soil C and N were greater in F-W-W-H-H-H than in GM-W-W and lowest in F-W-W (all unfertilized). Straw removal had no significant effect on C or N. The analysis showed that C inputs from crop residues was the main factor influencing SOC changes.
Tractor-mounted precision seeder, for sowing single grains by means of suction applied tn hypodermic needles, is described.
Surface seeding of crops has long been practiced with mixed results. Interest in this practice recently increased in irrigated agriculture with the development of an attachment for center pivot irrigation systems that applies seeds to the soil. This practice has been labeled seedigation. Mixed results have occurred from field experiments that were conducted to evaluate seedigation. A growth chamber study was conducted to determine the effect of relative humidity, soil water content, and irrigation frequency on the germination and establishment of surface seeded corn. The moisture content of corn seeds during imbibition and the germination rate were measured for seeds sown on a silty clay loam soil maintained at 15 and 25% gravimetric soil water contents. The experiments were conducted in growth chambers where the relative humidity was maintained at 70, 80, and 90% and the temperature at 25°C (77°F). The soil was rewetted either twice daily or every other day to study the effect of irrigation frequency. For the conditions studied, the relative humidity of the air had more effect on the seed moisture content and germination than either the soil water content or the frequency of watering. Germination rates exceeded 90% when the relative humidity was 90%. Germination rates were below 50% when the relative humidity dropped to 80% regardless of the soil water content. Increasing the soil water content from 15-25% improved germination rates and reduced the time required for germination. The frequency of watering had mixed results for these experiments, thus we were unable to show significant differences for watering frequency. The effects of watering frequency were smaller than effects for either humidity or soil water content.
(...) When a soil is compacted, bulk density increases and porosity decreases as larger pores are compressed, producing a soil with a greater proportion of fine pores. The resulting soil has a reduced capacity for the movement of water and air, and offers greater resistance to root penetration. Compaction increases the diffusion rate of nutrients, as soil particles are moved closer together. This effect may, in fact, increase nutrient uptake per unit length of root; however, total plant uptake is generally reduced because the increased root penetration resistance reduces root growth. (...)
This chapter discusses the magnitude and dynamics of the soil organic carbon (SOC) and soil inorganic carbon (SIC) pools. The chapter also describes the impact of different land uses and management systems on these pools as sources or sinks of C in relation to the global C cycle and the potential greenhouse effect. The principal objective of the chapter is to collate and synthesize available information on the soil C pool, historic loss of the soil C pool, the impact of land use and management practices that make the soil a source or sink for C, and the potential of world cropland soils to sequester C and mitigate the accelerated greenhouse effect. The strategy of soil C sequestration is a short-term, a partial solution to the potential risk of the accelerated greenhouse effect. Soil C sinks, as a major component of the net biome productivity, are important over short periods of time, but are not enough on a long-term basis to offset fossil-fuel emissions.
T HIS guideline contains descriptions of machines used for planting in conservation-tillage conditions and of soil-engaging components for those machines. The functions of available components are discussed relative to soil and crop residue conditions that may be encountered with conservation tillage. The guideline aids in determining planting machine specifications by identifying components that will work best under specific anticipated conditions. The user can then match those specifications with available commercial machines or modify existing machines by adding the desired components. INTRODUCTION Conservation-tillage planting conditions require the use of special "conservation-seeders," such as special row-crop planters, drills, or air-type seeders. Conservation-seeders are machine which have been designed or modified to be different machines or to have different machine components than those which have been designed for planting into residue-free tilled seedbeds. Farmers, as well as action-agency personnel, consultants, and other farm advisors need to be aware of the machine requirements for conservation-tillage planting. Because many machines have been developed and marketed in specific regions, local advisors and farmers are not necessarily familiar with the availability and performance capabilities of special machines and component options.
Six techniques of sowing seed in an untilled seedbed, which subsequently became wet, were compared in the presence and absence of earthworms and surface residue. In the absence of earthworms, surface broadcasting produced the highest seedling emergence (89%), followed by a 100-mm-wide power-till opener (42%). All other openers produced poor seedling emergence (mean 20%). Where earthworms were present, however, a winged opener under residue produced high seedling counts equivalent to surface broadcasting (mean 82%). Power-till and hoe openers also performed reasonably well (63%), but triple-disc and corer openers failed (19%). Surface broadcasting was not considered practical because of its reliance on regular rain for a long period.Surface residues in the presence of earthworms had beneficial effects on most of the openers which performed well and which separated the seed from the residue, but little effect on the other treatments, including the power-till opener. High seedling-emergence counts were associated with high numbers and activity of earthworms close to the sown groove, high soil oxygen diffusion rate regimes, low soil bulk densities and high root and shoot weights.
An experimental zero-traffic system was compared with a conventional-traffic system over four seasons in Scotland for both ploughed and direct-drilled winter barley seedbeds. A mouldboard plough was used for primary cultivation in both zero- and conventional-traffic plots in the first season, but a chisel plough was used in the ploughed treatments in subsequent seasons. After mouldboard ploughing in the first season, all wheels of both zero-traffic systems were restricted to permanent wheel tracks and all crops were sown in the bed between them. The crop yield for the ploughed zero-traffic system was never exceeded, although in the second season all yields were similar. Overall mean yield decreased with increasing rainfall in the spring and with decreasing soil permeability to air close to the soil surface. Soil compaction by wheels depressed plant populations under direct drilling in wet autumns, especially below wheel tracks in the direct-drilled conventional traffic system. Compaction also occurred in the absence of traffic under direct drilling. Vertical migration of earthworms was assumed to be responsible for some soil structural improvement at depth and, hence, successful direct drilling for both traffic systems, but after wet seasons crop establishment may also require shallow cultivation prior to drilling. After the fourth harvest, the draught force for primary cultivation averaged 17% more for each conventional-traffic system than for the corresponding zero system.