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Legume Decomposition and Nitrogen Release When Applied as Green Manures to Tropical Vegetable Production Systems


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For legume green manures (GM) to be effective, environmentally sound N sources for horticultural crops in the tropics, their N release must be in synchrony with crop N demand. Decomposition and N release of surface applied (mulch) or incorporated soybean [Glycine max (L.) Merr.] and indigofera (Indigofera tinctoria L.) GM were studied in six field studies conducted at three locations in Taiwan and the Philippines between 1993 and 1995. Litter bags and inorganic N soil samplings were used in order to understand tomato (Lycopersicon esculentum Mill.) crop responses to GM N. Resulting soil N contents were compared with a control (no GM, no fertilizer). The N content of 60 to 74 d soybean GM varied between 110 and 140 kg N ha-L and that of indigofera between 5 and 40 kg N ha(-1). Nitrogen-15-labeled soybean GM was traced in the soil and in organic matter fractions (humic acids, calcium humates, humins) in one of the field studies. Soybean and indigofera decomposed rapidly, losing 30 to 70% of their biomass within 5 wk after application, depending on GM placement, season (wet vs. dry), and location. Soil nitrate contents increased corresponding to GM N release at all locations and seasons, with a maximum increase of 80 to 100 kg NO3-N ha(-1) with incorporated soybean. The peak N release occurred 2 to 6 wk after GM application in two of the three locations, and 5 to 8 wk in the third location. The apparent decline of GM N release at all locations and seasons 8 wk after application was only partly caused by tomato N uptake. At tomato harvest, 30 to 60% of the GM N-15 was found in the soil, and was found mostly in humins. Comparable N release dynamics across seasons and locations suggest a possible N fertilizer substitution by incorporated soybean GM for basal N application and first side dressing to tomato. With respect to season and location, GM N should be supplemented with N fertilizer starting after 8 wk to ensure optimal tomato yields.
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Vallis, I. 1983. Uptake by grass and transfer to soil of nitrogen from
N- of transplanted fresh-market tomatoes as affected by plastic mulch
labeled legume materials applied to a rhodesgrass pasture. Aust. J. and initial nitrogen rate. J. Am. Soc. Hortic. Sci. 112(5):759–
Agric. Res. 34:367–376. 763.
Vasilas, B.L., J.D. Legg, and D.C. Wolf. 1980. Foliar fertilization Yaacob, O., and G.J. Blair. 1980. Mineralization of
N-labeled legume
of soybeans: Absorption and transformation of
N-labeled urea. residues in soils with different nitrogen contents and its uptake by
Agron. J. 72:271–275. Rhodes grass. Plant Soil 57:237–248.
Varco, J.J., W.W. Frye, M.S. Smith, and C.T. MacKown. 1989. Tillage Zebarth, B.J., V. Alder, and R.W. Sheard. 1991. In situ labeling of
effects on nitrogen recovery by corn from a nitrogen-15 labeled legume residues with a foliear application of
N-enriched urea
legume cover crop. Soil Sci. Soc. Am. J. 53:822–827. solution. Commun. Soil. Sci. Plant Anal. 22:437–447.
Wien, H.C., and P.L. Minotti. 1987. Growth, yield and nutrient uptake
Legume Decomposition and Nitrogen Release When Applied as Green Manures
to Tropical Vegetable Production Systems
Carmen Tho
¨nnissen, David J. Midmore, Jagdish K. Ladha, Daniel C. Olk, and Urs Schmidhalter*
ABSTRACT alogy and acidity, biological activity, and the presence
of other nutrients (Myers et al., 1994). In a previous
For legume green manures (GM) to be effective, environmentally
study, 60-d-old soybean [Glycine max (L.) Merr.] and
sound N sources for horticultural crops in the tropics, their N release
indigofera (Indigofera tinctoria L.) plants conformed to
must be in synchrony with crop N demand. Decomposition and N
high-quality litter characteristics (Swift, 1987), releasing
release of surface applied (mulch) or incorporated soybean [Glycine
max (L.) Merr.] and indigofera (Indigofera tinctoria L.) GM were
N quickly to two of the three soils tested (Tho
studied in six field studies conducted at three locations in Taiwan and
Michel, 1996). Legume biomass accumulation and
the Philippines between 1993 and 1995. Litter bags and inorganic N
chemical composition (e.g., C/N, N, lignin, polyphenol,
soil samplings were used in order to understand tomato (Lycopersicon
and tannin) of plants of the same age varied between
esculentum Mill.) crop responses to GM N. Resulting soil N contents
location and growing season (Tho
¨nnissen Michel, 1996),
were compared with a control (no GM, no fertilizer). The N content
making it difficult to predict their decomposition when
of 60 to 74 d soybean GM varied between 110 and 140 kg N ha
grown under different conditions. Residue decomposi-
and that of indigofera between 5 and 40 kg N ha
. Nitrogen-15-
tion can be governed to some extent by GM placement
labeled soybean GM was traced in the soil and in organic matter
on the soil surface (mulch) or incorporation into the
fractions (humic acids, calcium humates, humins) in one of the field
soil (Wilson and Hargrove, 1986). In the southeast of the
studies. Soybean and indigofera decomposed rapidly, losing 30 to 70%
of their biomass within 5 wk after application, depending on GM
USA, the greatest N release from decomposing legumes
placement, season (wet vs. dry), and location. Soil nitrate contents
occurred 2 to 5 wk after cover crop killing in spring
increased corresponding to GM N release at all locations and seasons,
(Sarrantonio and Scott, 1988). Too rapid GM N release
with a maximum increase of 80 to 100 kg NO
–N ha
with incorpo-
(e.g., within 15 d after incorporation of vetch; Varco et
rated soybean. The peak N release occurred 2 to 6 wk after GM
al., 1989), strong N immobilization after GM addition
application in two of the three locations, and 5 to 8 wk in the third
(Mary and Recous, 1994), or early decline of mineral
location. The apparent decline of GM N release at all locations and
N level over the growing season (Ebelhar et al., 1984)
seasons 8 wk after application was only partly caused by tomato N
lead to poor synchronization between N release and
uptake. At tomato harvest, 30 to 60% of the GM
N was found in
crop N demand. Studies evaluating the fate of
N from
the soil, and was found mostly in humins. Comparable N release
legume residues decomposing under field conditions led
dynamics across seasons and locations suggest a possible N fertilizer
substitution by incorporated soybean GM for basal N application and
to the conclusions that 30% of legume N was recov-
first side dressing to tomato. With respect to season and location,
ered by a subsequent nonlegume crop and large
GM N should be supplemented with N fertilizer starting after 8 wk
amounts of legume N were retained in soil, mostly in
to ensure optimal tomato yields.
organic forms (Harris et al., 1994; Ladd et al., 1983;
Mueller and Sundman, 1988). If, however, lower miner-
alization rates of mulched GM (nontillage) are responsi-
or legume green manures (GM) to be considered ble for reduced inorganic N accumulation, then such a
as effective N sources for horticultural crops, they system could better conserve organic N in the long term
must supply sufficient N and their N release must be in (Sarrantonio and Scott, 1988).
synchrony with vegetable N demand. Green manure The objective of this study was to monitor legume GM
decomposition and subsequent N release depend largely decomposition and determine the timing and quantity of
on residue quality and quantity, soil moisture and tem- GM N release in fields grown to tomato crops (Tho
perature, and specific soil factors such as texture, miner- sen Michel, 1996) at three locations and two seasons
(wet season, WS; dry season, DS) in Taiwan and the
Philippines. In the tropical WS in Taiwan, nitrate leach-
C. Tho
¨nnissen and D.J. Midmore, The Asian Vegetable Res. & Dev.
Ctr., P.O. Box 42, Shanhua Tainan, Taiwan ROC; J.K. Ladha and
D.C. Olk, IRRI, P.O. Box 933, Manila 1099, Philippines; U. Schmid-
Abbreviations: AVRDC, Asian Vegetable Research and Develop-
halter, Dep. of Plant Nutrition, Technische Universita
ment Center; BRCI, Bukidnon Resources Corporation, Inc.; DS, dry
Freising-Weihenstephan, D-85350 Germany. Received 12 Aug. 1998.
season; IRRI, International Rice Research Institute; GM, [legume]
*Corresponding author (
green manure; MMSU, Mariano Marcos State University; SOM, soil
organic matter; WS, wet season.Published in Agron. J. 92:253–260 (2000).
42, 62 and 75 d after GM application, at AVRDC DS 0, 7,
ing losses were estimated in tomato plots amended with
21, 35, 56, 98 d after GM application, and at MMSU 0, 5, 21,
GM and N fertilizer. To trace the fate of GM N at one
36, 58, 77, 113 d after GM application. On each date two
of the three locations,
N-labeled GM was traced in soil
randomly chosen bags per treatment were retrieved, oven-
and labile fractions of soil organic matter.
dried at 60C for 48 h, and weighed. Samples were ashed by dry
combustion in a muffle furnace (500C) for 8 h to determine
original ash-free dry weight remaining (Aber et al., 1990).
Biomass loss data for soybean and indigofera were fitted into
Field Trials
the first-order single exponential model M
for litter decomposition by Wieder and Lang (1982). The
Legume GM decomposition and subsequent N release to higher the k-value (decomposition rate), the faster the decom-
soil grown to tomato (Lycopersicon esculentum Mill.) crops position of the organic matter. Decomposition rates were cal-
was monitored in six field experiments during 1993 to 1995 culated for a period of 77 d in the WS and 94 d in the DS at
conducted at the Asian Vegetable Research and Development AVRDC and 113 d at MMSU.
Center (AVRDC) in central Taiwan, the Mariano Marcos
State University (MMSU) in northern Luzon in the Philip-
Inorganic Nitrogen
pines, and the Bukidnon Resources Co., Inc. (BRCI), in north-
ern Mindanao in the Philippines. Experiments were run simul- The effects of legume species and GM placement treatments
taneously on two fields, each with different bed systems: raised on the quantity and the timing of N release to soil were evalu-
or low beds. The raised beds were 45 cm high and 2 m wide, ated in all six field experiments. Inorganic N in the soil was
with 2-m furrows between the beds. The furrows were sown monitored in plots planted to tomato in five treatments; con-
with rice (Oryza sativa L.) and were permanently flooded. trol (Ck0), soybean incorporation (Si), soybean mulch (Sm),
The low beds were 20 cm high and 2 m wide, with 50-cm-wide and either indigofera incorporation (Ii) and indigofera mulch
irrigation furrows between beds. Both experiments (raised (Im) (at AVRDC and MMSU) or mungbean incorporation
and low beds) were adjacent, such that the soil type, the (Mi) and mungbean mulch (Mm) (at BRCI). These plots were
cropping history, and meteorological conditions were the sampled on the dates listed above for litterbag sampling and
same. Soil types were a silt-loamy, mixed, hyperthermic Fluva- also at 0, 14, 28, 42, 56, 70, 84, 96, 110 d after GM application
quentic Entochrept (AVRDC); a clayey, kaolinitic, isohyper- at BRCI. Soil samples were collected with a 5-cm-diameter
thermic Ultisol (BRCI); and a clayey, mixed, isohyperthermic auger at the 0- to 30-cm depth from the five treatments in all
Fluvaquentic Ustropept (MMSU). A randomized complete four blocks. Each sample was a mixed composite collected
block design with four replicates was used at all three locations. from four locations in each plot. Soil samples were passed
Treatments at each location were two legume species, two through a 10-mm sieve and extracted with 1 MKCl (1:1.5 soil/
methods of GM application to the soil, and four N treatments water); inorganic N (NH
–N and NO
–N) was determined with
(0, 30, 60, and 120 kg N ha
) applied to tomato. Legumes an ammonia gas sensing electrode (Siegel, 1980). At MMSU,
were grown for 2 mo, cut at the root level, chopped, and additional soil samples from the 30- to 60-cm soil depth were
applied to the soil. The legumes were soybean and indigofera taken at 74 (legume seeding), 1, and 113 d after GM appli-
at AVRDC and MMSU, and soybean and mungbean [Vigna cation.
radiata (L.) Wilcz.] at BRCI. Once GM was applied to the To study the effect of living plants on N mineralization, the
soil, tomato crops were transplanted on the same location and five treatment plots in Blocks I, II, and III were split into
grown up to harvest (2–3 mo) (Tho
¨nnissen Michel, 1996). three subplot treatments after GM application: (i) unplanted,
Leguminous green manures (60 d old at AVRDC; 70 d old (ii) planted with tomato, and (iii) planted with cabbage (Bras-
at MMSU) were incorporated by soil tillage down to the 10- sica oleracea var. capitata L.) in the DS at AVRDC; and (i)
to 15-cm soil depth or left as mulch on the soil surface (no unplanted, (ii) planted with tomato 1 d after GM application,
soil tillage). The amounts of legume biomass and N present as and (iii) planted with tomato 2 wk after GM application at
GM varied across locations and seasons. For example, soybean MMSU. Nitrogen mineralization was monitored in all three
GM contained between 110 and 140 kg N ha
, indigofera subplot treatments.
between 5 and 40 kg N ha
, and mungbean 26 kg N ha
¨nnissen Michel, 1996). Tomato seedlings were trans-
Estimation of Potential Nitrate Leaching
planted immediately after GM application and remained in
the field until fruit harvest. Nitrate leaching in the WS at AVRDC was estimated by
the NaCl method (Cameron and Wild, 1982). Fifty grams of
NaCl was broadcast on 1 m
in the tomato plots in the treat-
Environmental Monitoring
ments Si, Sm, Ck0, and 120 kg N ha
(Ck120) in four replica-
Soil moisture was monitored with tensiometers placed in tions in two bed systems, low or raised beds (Tho
GM and control treatments, at the 15-, 30- and 45-cm depths Michel, 1996). Sodium chloride was applied on the respective
following tomato transplanting at AVRDC and MMSU. plots after soybean incorporation and mulch on 23 June 1993.
Soil samples were taken on 21 June, 23 July, and 30 August
from the 0- to 50-cm layer in the raised beds and from the 0-
Decomposition Study
to 30-cm layer in the low beds. In each, the soil core was
Nylon bags (mesh size 1 mm) containing 15 g fresh plant separated into 10-cm sublayers. Soil samples were air-dried
material (4.7–5.5 g dry wt.) were used to determine biomass and extracted (1:2 soil/water). Chloride in the water extracts
breakdown of incorporated or mulched soybean and in- was determined with a chloride analyzer (Chloride Analyzer
digofera GM at AVRDC in both the WS and the DS and at 926, Coramed AG, Dietlikon, Switzerland).
MMSU in the DS only. Bags were filled with root and shoot
material on the same day as GM application. Mulch treat-
Nitrogen-15 Experiment
ments contained shoot material only. At the time of GM
application, all bags were either buried 10 cm deep for incorpo- Tomato N response to GM was low in the DS at AVRDC
¨nnissen Michel, 1996). To understand the fate of GM N,ration treatments or left on the surface for the mulch treat-
ments. Litter bags were sampled at the same dates as soil soybean GM was labeled with
N (Tho
¨nnissen Michel, 1996)
for a
N microplot experiment at MMSU. Microplots (metalsampling for inorganic N: at AVRDC WS 0, 2, 5, 8, 14, 29,
Fig. 1. Decomposition of soybean and indigofera residues when used as mulch or incorporated into the soil in the low and raised bed systems
and in the wet and dry seasons at AVRDC, Taiwan, and in the dry season at MMSU, Philippines (1993–1995). Error bars indicate LSD (0.05).
frames 0.8 by 0.8 by 0.3 m, length by width by height, pushed
species at AVRDC, while soybean and indigofera de-
into the soil to a depth of 25 cm) were amended with
composed differently at MMSU. Great differences in
labeled soybean GM. The GM was incorporated manually
decomposition between incorporated and mulched indi-
down to the 10- to 15-cm soil depth. Two tomato seedlings
gofera occurred during the early decomposition stages
were transplanted into each microplot. Green manure
(up to 6 wk) at MMSU (Fig. 1). With the exception of
recovery in tomato was determined (Tho
¨nnissen Michel,
incorporated indigofera, GM at MMSU decomposed at
1996). Soil was sampled for organic matter extraction and
reduced rates compared with those at AVRDC.
N determination in control and soybean incorporation
treatment plots at 1 and 113 d after GM application. Nitrogen-
15 determination was conducted on mobile humic acids
Soil Moisture and Nitrogen Release
(MHA) and calcium humates (CaHA), which were considered
Frequent irrigation precluded significant changes in
as C pools representing early and later stages of the humifica-
soil moisture due to GM placement during the tomato
tion process (Olk et al., 1995).
growing season in the DS at AVRDC and at MMSU.
An optimal water supply for tomato plants was ensured
Statistical Analysis
by maintaining soil matric potentials between 0.02 and
Data were analyzed by ANOVA procedure using JMP Ver-
0.06 MPa. With the exception of typhoons that hit
sion 2 (SAS Inst., 1989) and SAS version 6.03 (SAS Inst., 1991).
southern Taiwan irregularly and subsequently flooded
the low beds, soil matric potentials ranged between
0.01 and 0.08 MPa in the WS. Daily rainfall led to
soil moisture contents near field capacity during the
At all locations and seasons, incorporated GM de-
tomato growing season at the BRCI location.
composed significantly faster than mulched GM (Fig.
Nitrate was the dominant form of inorganic N in the
1). Biomass loss patterns and decomposition rates of
soil soon after legume application at all three locations.
both legume species and GM management practices
Soil NH
–N contents remained low (5kgNH
–N ha
were comparable across bed systems at AVRDC (Table
at AVRDC and MMSU; 20 kg NH
–N ha
at BRCI)
1). Soybean decomposed slightly faster than indigofera
and were comparable to those of the control (data not
in the WS, but slower than indigofera in the DS at
shown). Green manure application increased soil
AVRDC. Differences in biomass breakdown between
–N contents significantly by 10 to 15 kg NH
–N ha
GM placement (mulch vs. incorporation) at AVRDC
at AVRDC, 5 kg NH
–N ha
at MMSU, and 30 kg
were larger in the DS than in the WS. While decomposi-
–N ha
at BRCI in the first week after GM applica-
tion rates of incorporated GM were similar across sea-
tion, but NH
–N declined rapidly within 3 wk. With the
sons at AVRDC, those of mulched soybean GM in the
exception of an increase in soil NH
–N by 1 to 8 kg
DS were only half those of the WS, and slightly greater
–N ha
in the low beds in the DS at AVRDC,
than those of the WS for indigofera. The effect of GM
placement on biomass loss was similar across legume NH
–N contents did not differ between planted and
Table 1. Decomposition rate, k, of legume green manures (soybean, indigofera) incorporated into the soil or left as mulch on the soil
surface in field experiments at AVRDC, Taiwan (1993–1994) and at MMSU, Philippines (1994–1995). Decomposition rates were
calculated using the single exponential model for decomposition (Wieder and Lang, 1982), for a period of 77 d in the wet season
(WS) and 94 d in the dry season (DS) at AVRDC and 113 d at MMSU.
Species Plant age d† Application Location Season Bed system k‡d
Soybean 68 incorporation AVRDC WS raised 0.0272a 0.89***
low 0.0361a 0.88***
60 DS raised 0.0236c 0.95***
low 0.0251c 0.80*
74 MMSU DS low 0.0099e 0.96***
68 mulch AVRDC WS raised 0.0175b 0.91***
low 0.0144b 0.90***
60 DS raised 0.0094d 0.89**
low 0.0071d 0.95***
74 MMSU DS low 0.0065f 0.64*
Indigofera 68 incorporation AVRDC WS raised 0.0266g 0.88***
low 0.0262g 0.93***
60 DS raised 0.0313i 0.94**
low 0.0350i 0.97***
74 MMSU DS low 0.0259k 0.67*
68 mulch AVRDC WS raised 0.0098h 0.75**
low 0.0111h 0.91***
60 DS raised 0.0162j 0.98***
low 0.0147j 0.95**
74 MMSU DS low 0.0059l 0.52NS
† d, days after sowing.
k-values within the same season, location, and bed system were compared using a pairwise t-test for slopes. K-values with different letters are significantly
different at P0.05.
§ *,**,***, NS, Regressions are significant at P0.05, 0.01, 0.001, or nonsignificant, respectively.
unplanted plots in the raised beds at AVRDC and at the end of the experiment. At tomato harvest, less soil
was found in planted than in unplanted plots, butMMSU.
At all three locations, N release in soil peaked at 80 differences were not significant. Green manure applica-
tion did not affect NH
contents at the 30- to 60-cmto 120 kg NO
–N ha
with soybean GM (Fig. 2). This
peak N release occurred 2 to 6 wk after GM application soil depth.
in both seasons at AVRDC and at BRCI. At MMSU,
Nitrate Leaching
GM N release peaks were delayed relative to the two
other locations, occurring after 5 to 8 wk. Nitrate con- The potential for nitrate leaching estimated from the
tents declined after 5 to 8 wk at all locations. More movement of chloride followed similar patterns in con-
–N was released with incorporated GM than trol, 120 kg N ha
, soybean mulch and incorporation
mulched GM at AVRDC and MMSU. Far more N was treatments. Therefore, chloride loss (%) data of these
released with soybean than indigofera in the WS at four treatments were averaged for each sampling date
AVRDC; in the DS, however, differences in N release and bed system (Table 2). The background Cl-concen-
between legume species were small. Nitrate released tration (21 June) in the 10- to 50-cm soil depth was
with soybean GM was comparable to that released with rather low. Of the applied chloride, 42 and 50%, had
been lost by 23 July 1993 from a soil depth of 30 and
mungbean GM at BRCI. Basal N mineralization
50 cm, respectively, in the raised bed only 1 mo after
–N) in control treatment plots was low in the WS application. The greatest net loss occurred at the 0- to
at AVRDC and at MMSU, but high in the DS at 10-cm soil depth, whereas chloride accumulation oc-
AVRDC and at BRCI. curred at soil depths of 10 to 20 cm and 20 to 30 cm.
From 10 to 50 kg ha
less of NO
–N was measured Chloride did not accumulate at the 30- to 50-cm depth
in planted than in unplanted plots between 3 and 8 wk in the raised beds.
after GM application in the DS at AVRDC (data not
shown). Nitrogen uptake by tomato or cabbage, mea-
Green Manure Nitrogen-15 Recovery in Soil
sured by the difference of NO
in the soil in planted
vs. unplanted plots, generally started 1 to 3 wk after Total soil C and N contents increased by about 5%
between the time of soybean incorporation and tomatotransplanting. Cabbage was apparently a strongerN sink
than tomato, for less soil NO
was found in cabbage harvest (Table 3). Although mobile humic acid (MHA)
C increased and calcium humate (CaHA) C and N de-than tomato plots. At MMSU, soil NO
–N contents in
early-transplanted tomato plots remained lower than in creased from the first to the second sampling, the effect
of GM application on these parameters is not cleareither later-transplanted plots or in the unplanted con-
trol plots (data not shown). No significant differences because these parameters changed similarly in the con-
trol plot between soil NO
–N content between GM and control plots
were evident at the 30- to 60-cm soil depth at MMSU. The MHA and CaHA did not seem to be more active
in short-term N cycling than the bulk soil organic matterHowever, nitrate contents at the 30- to 60-cm soil depth
in GM treatments tended to be lower than the control (SOM), as the two fractions combined contained only
4.5% of the total soil
N in the soybean plot at tomatobefore GM application and higher than the control at
Fig. 2. Nitrate contents in soil (0–30 cm) after application of green manure (soybean, indigofera at AVRDC, Taiwan, and at MMSU, Philippines;
soybean and mungbean at BRCI, Philippines) in raised (R) and low (L) beds, 1993–1995. Error bars indicate LSD (0.05); asterisk indicates
significance at the 0.1 probability level.
harvest. Most of the
N was recovered in the humin
(unextracted organic matter). Moreover, the ratios of
Factors Affecting Green Manure Decomposition
N to total N were similar for the MHA and CaHA as
and Mineralization
for the bulk soil, further suggesting that preferential
Decomposition rates of incorporated GM differed
accumulation of recently added
N did not occur in the
less between seasons and locations than for mulched
extracted MHA and CaHA. The MHA and CaHA had
GM. Incorporated residues are in a generally more fa-
comparable amounts of
N in the soybean plots at final
vorable environment for microbial decomposition (e.g.,
tomato harvest. Nitrogen-15 in total soil was not fully
close soil contact, adequate soil moisture, etc.) (Wilson
recovered in the MHA, CaHA, and humin, which may
and Hargrove, 1986). Fast initial decomposition of soy-
be due to losses of
N during extraction as fulvic acids.
bean in both seasons at AVRDC matches findings of
At tomato harvest, estimations of N losses were
greater calculated with
N than with total N (Table 4), Broder and Wagner (1988), where incorporated soy-
due to lower N recoveries of
N in both tomato and soil. bean residues lost 68% of their total biomass within 32 d.
Nitrogen-15 values for whole soils, MHA, and CaHA for In most comparisons, plant chemical composition ap-
all treatments except soybean at tomato harvest were peared to affect the decomposition rate of GM. Faster
too low to allow accurate measurement. decomposition of indigofera at AVRDC was probably
caused by its smaller and more tender leaves and less
Table 2. Percent remaining chloride at different soil depths for
three sampling dates in raised and low beds (AVRDC, Taiwan, Table 3. Organic C and N in total soil and in organic fractions
1993). Chloride was added on 23 June. (mobile humic acids [MHA]; calcium humates [CaHA] imme-
diately after (1 d) and 113 d after green manure application in
control and soybean incorporation plots. Standard deviation
Soil depth 0–10 10–20 20–30 0–30 30–40 40–50 0–50
of laboratory replicates of organic C and N contents of total
soil are given in parentheses, 1994–1995, MMSU, Philippines.
Raised beds
Total soil
Organic matter fraction
21 Jun 78 46241 100 7 151 100
23 Jul 24 61216237514150 MHA CaHa
30 Aug 14 2925125313135
Low beds
21 Jun 86 38361 100 gkg
23 Jul 28 10 19 411258 1
30 Aug 23 116411250 Control 7.11 (0.01) 0.665 (0.01) 0.162 0.0163 0.448 0.0409
Soybean 7.04 (0.03) 0.707 (0.01) 0.218 0.0227 0.369 0.0346
Values shown are means of four treatments: control, Ck 120 kg N ha
soybean incorporation, and mulch, and standard deviation between treat- 113
ment means. Treatments means are means of four replicates. Control 6.85 (0.06) 0.669 (0.02) 0.212 0.0204 0.228 0.0243
† % Cl was calculated by setting the Cl contents (g Cl/m
) to 100% on 21 Soybean 7.39 (0.04) 0.750 (0.02) 0.240 0.0231 0.226 0.0248
June 1993 from 0 to 30 cm (raised and low beads), and additionally 0
to 50 cm for raised beds. † d, days after soybean GM application.
Table 4. Comparison of total N and
N balance after tomato
N-ratio (10.6) and higher initial N content (4.2%) of
harvest in soybean incorporation plots at MMSU, 1995. Values
indigofera may have determined its faster decomposi-
within parentheses indicate standard deviation (n3).
tion compared with soybean (C/N 12.2; N 3.9%). Results
Total N
of this study confirm the complexity of decomposition
% recovery kg N ha
% recovery
processes where the interaction of both resource quality
and microclimate influence the conditions and activity
Input soybean 119.3 0.910
Output tomato 19.5† (10.8) 16.3 0.082 (0.02) 8.9
of decomposer communities and those in turn mediate
left soil 64.0 (20.0) 53.7 0.315 (0.01) 34.6
processes of decomposition and nutrient release (Neely
not found 35.8 30.0 0.513 56.5
et al., 1991; Hunt, 1977).
Calculated by subtracting tomato N in control from tomato N in soy-
High soil temperatures (20–30C) and moisture condi-
bean incorporation.
tions near optimum (0.01 to 0.05 MPa; Cassman
and Munns, 1980) were mainly responsible for the fast
release of NO
following GM application in all locationslignified stems relative to those of soybean. The slower
decomposition of incorporated soybean compared with and seasons. Nitrate-N release at AVRDC mirrored
the initial exponential loss of biomass, evidence for theindigofera at MMSU occurred despite similar plant
chemical compositions (data not shown). Sixty-day-old causal linkage between these two processes. Higher de-
composition rates of indigofera in the DS led to N re-soybean (maturity scale R5 to R6; Fehr et al., 1971) in
both seasons at AVRDC decomposed at rates similar lease in soil comparable to that of soybean, although
far less N (33 vs. 127 kg N ha
, Tho
¨nnissen Michel,to those of incorporated indigofera at MMSU. The phys-
ical nature of older soybean plant material (R6 to R7) 1996) was incorporated with indigofera GM. Reduced
mineralization rates of surface applied residues (mulch)used at MMSU, with hardy stems and pods containing
full size yellow beans, may have been one of the main can be attributed to poor soil–residue contact and dras-
tic temperature and moisture fluctuations at the soilreasons for the large differences in decomposition rates
between soybean decomposition at AVRDC and indi- surface (McCalla and Duley, 1943). Numerous authors
(e.g., Janzen and McGinn, 1991) have stressed the im-gofera at MMSU.
Many investigators have observed that organic resi- portance of volatilization losses when GM is applied as
surface mulch, since drying and decomposing conditionsdues decompose more slowly in soils with higher clay
contents, especially clays having higher exchange capac- enhance volatilization. The volatile loss of labile N from
decomposing GM mulch may appreciably diminish itsities (Lynch and Cotnoir, 1956; Sorensen, 1975). Micro-
bial activity is controlled by soil physical conditions such fertility benefit, whereas NH
losses from incorporated
GM have been reported to be negligible (Janzen andas compaction, temperature and oxygen; by chemical
conditions such as substrate availability; and by biologi- McGinn, 1991). If, however, lower mineralization rates
are the cause of reduced inorganic N accumulation un-cal conditions such as predatory or antagonistic organ-
isms (Grant et al., 1993). Reduced soil aeration or oxy- der no-tillage, then such a system could better conserve
organic N in the long term (Sarrantonio and Scott, 1988).gen in the clayey soil at MMSU compared with the
loamy soil at AVRDC may have further contributed to Slight increases in NO
contents in the soil 10 wk after
GM application in the WS at AVRDC and at BRCIa slower legume residue decomposition rate at MMSU.
The exponential weight loss pattern agrees with previ- (Fig. 2) may indicate remineralization of N that had
been immobilized earlier, even though the process isous assumptions that residues contain labile and recalci-
trant fractions having different degrees of resistance to considered to be relatively slow in temperate soils (Mary
and Recous, 1994). Lowest NO
–N contents in the soilmicrobial degradation. Reinertsen et al. (1984) associ-
ated the more rapid decay immediately after the burial with indigofera mulch were likely due to the NO
uptake of the indigofera (Tho
¨nnissen Michel, 1996).of the residue with the decomposition of water-soluble
organic constituents. Hunt (1977) described differences Although N release dynamics may have been driven
by a combination of location and/or season-specific fac-in decomposition patterns and rates among substrates
as a function of the amount of the labile or rapidly tors, N release patterns across locations and seasons are
similar. High leaching and denitrification losses in thedecomposing fractions (sugars, starches, proteins) and
the recalcitrant or slowly decomposing fraction (cellu- WS at AVRDC may have reduced the amount of GM
N available to tomato plants, although temperature andlose, lignin, fats, tannins, waxes). Decomposition pro-
cesses can be predicted from initial litter chemistry soil moisture were more favorable for N mineralization
than in the DS. Results of an incubation study compar-(Aber et al., 1990; Neely et al., 1991). Seasonal effects
on chemical composition of legumes (i.e., C/N, initial ing N release after addition of dry organic residues to
these three soils (Tho
¨nnissen Michel, 1996) suggestedN, lignin, polyphenol, and tannin contents) have been
shown within the same location (Tho
¨nnissen Michel, that certain soil chemical and physical properties re-
tarded N release in MMSU soil, relative to BRCI and1996). The statistical significance of each chemical com-
ponent to the rate of GM degradation varied widely AVRDC soil. Soil basal N mineralization was higher in
the AVRDC and BRCI soils than in the MMSU soilbetween seasons and locations (Tho
¨nnissen Michel,
1996). The relatively high polyphenol (3.7%) and tannin (Tho
¨nnissen Michel, 1996). Significant amounts of inor-
ganic N were detected in fallow plots lacking GM addi-(1.6%) content of indigofera may have retarded decom-
position compared with soybean (polyphenol 1.7%, tan- tion prior to vegetable crops in the DS at AVRDC
and at BRCI, while leaching losses may have preventednin 0.2%) in the WS, whereas in the DS the lower C/
nitrate accumulation in the WS at AVRDC. The higher
Total Nitrogen and Nitrogen-15 Balance
the soil N supply, the more legumes derive N from The similarities of the ratios of total
N to total N
soil rather than from biological N
fixation. Low NO
for MHA and CaHA fractions compared with humin
contents in legume plots can be explained by the effec- suggest that the two fractions were no more labile than
tiveness of legumes to assimilate NO
derived from soil the rest of the SOM in this soil. Our results are compara-
N mineralization (George et al., 1994; Ladha et al., ble to those of He et al. (1988), in that a significant
1996). proportion of recently added
N in the soil was not
At all locations and seasons, the decline of soil inor- extractable (humin). Humin can be very young and
ganic N at 6 to 8 wk after GM application may result much of it is composed of alkyl compounds and carbohy-
from a combination of the period of greatest N uptake drates as microbial byproducts (He et al., 1988). Domi-
by the tomato plants (Tho
¨nnissen Michel, 1996), lower nation of soil C and N by humin may be especially
rates of N mineralization (Griffiths et al., 1994) and pronounced in a soil where conditions are favorable for
biological N immobilization (Mary and Recous, 1994). degradation. The rapid decomposition of the soybean
The faster decline of soil nitrate in planted compared residues and the small quantities of MHA and CaHA
with unplanted plots suggests vegetable N uptake at extracted from the MMSU soil in relation to other rice
AVRDC and at MMSU. Using
N-labeled residues in soils of the Philippines (Olk et al., 1995) demonstrate
the absence of growing plants, Chotte et al. (1990) found the favorable conditions for degradation in this soil.
net immobilization in the organic residues, but net min- Organic molecules resulting from microbial degrada-
eralization occurred when plants were grown in these tion, such as microbial tissues, will be preserved in the
soils. Root exudates of vegetable crops may have been soil only if they are stabilized and thereby are protected
an insignificant energy source for soil microbial growth from further degradation. One such form of protection
(Martens, 1990) in our experiments because of the high is chemical binding to the mineral surface of such
degradability of our soybean and indigofera GM, and strength that the organic material is not extractable and
the favorable soil temperature and moisture conditions. hence considered as humin. The extremely high Ca lev-
Reduction of microbial activity and microbial N immo- els in MMSU soil may also contribute to the humin
bilization after consumption of the labile fractions of constituting a high proportion of total SOM.
the residue in early decomposition stages may have oc- Lower rates of
N recovery could be due to mineral-
curred due to the recalcitrance of the remaining crop ization–immobilization turnover. The
N released from
residue. It is possible that these recalcitrant organic frac- the legume residue into the soil inorganic pool could
tions lead to the formation of soil humus (Wilson and be exchanged for
N in microbial biomass, which could
Hargrove, 1986). If microbial N needs were large, avail- lead to lower
N recovery. Alternatively, lower rates
able soil inorganic N would be rapidly depleted and of
N recovery than total N may result partly from an
the decomposition rate of organic compounds would overestimation of apparent total N recovery and partly
decline (Mary and Recous, 1994), leading to N immobili- from the importance of soil conditions during the rapid
zation (6–8 wk) and delayed N remineralization. In ex- degradation of
N-labeled material. Higher mineraliza-
periments by Broadbent and Tyler (1962), NO
was tion rates of labeled than of unlabeled organic materials
immobilized to a considerable extent when it was the may have contributed to lower rates of N recovery in
only N form available to soil microorganisms. Mary and
N compared with total N balances, in agreement with
Recous (1994) described N immobilization–remin- other authors (Amato and Ladd, 1980; Chichester et
eralization following organic residue incorporation as a al., 1975). Greater loss of
N than total N (57 vs. 30%)
function of the amount and nature of the residues and may reflect volatilization and denitrification at the be-
soil mineral N, whereas basal mineralization was ex- ginning of the crop cycle, as well as the low plant N
plained as a function of soil texture and long-term C uptake at that time. Total N loss would be lower on a
and N inputs. percent basis during this time because of the low basal
It is probable that liming of the soil and the addition rate of SOM-N mineralization. Because labeled soybean
of poultry manure (Gallus sp.) led to a strong soil N was quickly decomposed, the fate of GM
N would be
mineralization in BRCI soil. Decay of plant residues disproportionately determined by soil conditions early
and SOM are accelerated by liming of acid soils (Alex- in the crop cycle. Given the relatively wet yet aerated
ander, 1977). conditions in the MMSU soil, these large amounts of
The great loss of Cl and ostensibly NO
within the
mineralized quickly from plant residues or young
first month of GM and N fertilizer application in the
SOM fractions would be prone to losses via volatiliza-
WS at AVRDC, probably resulted from two rainfall
tion or nitrification–denitrification. This scenario is sup-
events within that period. The soil at 30 cm depth in
ported by the low total soil C and N levels, small quanti-
the raised bed system was permanently submerged due
ties of extracted MHA and CaHA, high losses of
to the standing water in the rice beds (Tho
¨nnissen Mi-
from the system, and the greater relative loss of
N than
chel, 1996), so that Cl may have been leached with rice
total N.
bed irrigation. Improved infiltration rate through soil
Given its low total C and N contents, the MMSU soil
in the raised beds may have also increased leaching
may not have a large capacity to store added N, whether
losses (Shennan, 1992). Our results confirm those of
the N is added in organic or inorganic forms. We con-
Stute and Posner (1995), that potentially leachable soil
–N differed little following GM or N fertilizer. clude that the lack of synchronization between N supply
Ladha, J.K., D.K. Kundu, M.G. Angelo-Van Copenolle, M.B. Peoples,
and demand caused by a single application of GM
V.R. Carangal, and P.T. Dart. 1996. Legume productivity and soil
shortly before vegetable transplanting makes this treat-
nitrogen dynamics in lowland rice-based cropping systems. Soil Sci.
ment less successful than split applications of inorganic
Soc. Am. J. 60:182–192.
N (Tho
¨nnissen Michel, 1996).
Lynch, D.L., and L.J. Cotnoir, Jr. 1956. The influence of clay minerals
on the breakdown of certain organic substrates. Soil Biol. Bio-
chem. 20:367–370.
Martens, R. 1990. Contribution of rhizodeposits to the maintenance
Aber, J.D., J.M. Melillo, and C.A. McClauherty. 1990. Predicting and growth of soil microbial biomass. Soil Biol. Biochem. 22:
long-term patterns of mass loss, nitrogen dynamics, and soil organic 141–147.
matter formation from initial fine litter chemistry in temperate Mary, B., and S. Recous. 1994. Measurement of nitrogen mineraliza-
forest ecosystems. Can. J. Bot. 68:2201–2208. tion and immobilization fluxes in soil as a means of predicting net
Alexander, M. 1977. Mineralization and immobilization of nitrogen. mineralization. Eur. J. Agron. 3(4):291–300.
p. 225–250. In M. Alexander (ed.) Introduction to soil microbiology. McCalla, T.M., and F.L. Duley. 1943. Disintegration of crop residues
Wiley, New York. as influenced by subtillage and plowing. Agron. J. 35:306–315.
Amato, M., and J.N. Ladd. 1980. Studies of nitrogen immobilization Mueller, M.M., and V. Sundman. 1988. The fate of nitrogen (
and mineralization in calcareous soils. V. formation and distribu- released from different plant materials during decomposition under
tion of isotope-labeled biomass during decomposition of
C and field conditions. Plant Soil 105:133–139.
N labeled plant material. Soil Biol. Biochem. 12:405–411. Myers, R.J.K., C.A. Palm, E. Cuevas, I.U.N. Gunatilleke, and Bros-
Broadbent, F.E., and K.B. Tyler. 1962. Laboratory and greenhouse sard. 1994. The synchronization of nutrient mineralization and plant
investigations of nitrogen immobilization. Soil Sci. Soc. Am. nutrient demand. p. 81–116. In P.L. Woomer and M.J. Swift (ed.)
Proc. 26:459–462. The biological management of tropical soil fertility. Wiley-Sayce
Broder, M.W., and G.H. Wagner. 1988. Microbial colonization and Publication, Chichester, UK.
decomposition of corn, wheat and soybean residue. Soil Sci. Soc. Neely, C.L., M.H. Beare, W.L. Hargrove, and D.C. Coleman. 1991.
Am. J. 52:112–117. Relationship between fungal and bacterial substrate-induced respi-
Cameron, K.C., and A. Wild. 1982. Comparative rates of leaching of ration (SIR), biomass and plant residue decomposition. Soil Biol.
chloride, nitrate and tritiated water under field conditions. J. Soil Biochem. 23(10):947–954.
Sci. 33:649–657. Olk, D.C., K.G. Cassman, and T.W.M. Fan. 1995. Characterization
Cassman, K.G., and D.N. Munns. 1980. Nitrogen mineralization as of two humic acid fractions from a calcareous vermiculitic soil:
affected by soil moisture, temperature and depth. Soil Sci. Soc. Implications for the humification process. Geoderma 65:195–208.
Am. J. 44:1233–1237. Reinertsen, S.A., L.F. Elliot, V.L. Cochran, and G.S. Campbell. 1984.
Chichester, F.W., J.O. Legg, and G. Stanford. 1975. Relative mineral- Role of available carbon and nitrogen in determining the rate of
ization rates of indigenous and recently incorporated
N-labeled wheat straw decomposition. Soil Biol. Biochem. 16:459–464.
nitrogen. Soil Sci. 120:455–460. Sarrantonio, M., and T.W. Scott. 1988. Tillage effects on availability
Chotte, J.C., J. Louri, J.M. Hetier, C. Castellanat, E. de Guiron, of nitrogen to corn following a winter green manure crop. Soil Sci.
M. Clairon, and M. Mahieu. 1990. Effets de divers pre
´dents Soc. Am. J. 52:1661–1668.
cultutraux sur l’utilisation de l’azote par un maı
ˆs, apport d’urea SAS Institute. 1989. JMP user’s guide. Version 2 ed. SAS Inst.,
N sur quatre types de sols tropicaux (Petites Antilles). Agron. Cary, NC.
Trop. 45:67–73. SAS Institute. 1991. SAS user’s guide. Version 6.03 ed. SAS Inst.,
Ebelhar, S.A., W.W. Frye, and R.L. Blevins. 1984. Nitrogen from Cary, NC.
legume cover crops for no-tillage corn. Agron. J. 76:51–55. Siegel, R.S. 1980. Determination of nitrate and exchangeable ammo-
Fehr, W.R., C.E. Caviness, D.T. Burmood, and J.S. Pennington. 1971. nium in soil extracts by an ammonia electrode. Soil Sci. Soc. Am.
Stage of development descriptions for soybeans, Glycine max (L.) J. 44:943–947.
Merrill. Crop Sci. 11:929–931. Shennan, C. 1992. Cover crops, nitrogen cycling and soil properties
George, T., J.K. Ladha, D.P. Garrity, and R.J. Buresh. 1994. Legumes in semi-irrigated vegetable production systems. HortScience 27(7):
as nitrate catch crops during the dry-to-wet transition in lowland 749–754.
rice cropping systems. Agron. J. 86:267–273. Sorensen, L.H. 1975. The influence of clay on the rate of decay of
Grant, R.F., N.G. Juma, and W.B. McGill. 1993. Simulation of carbon amino acid metabolites synthesized in soil during the decomposi-
and nitrogen transformations in soil: Mineralization. Soil Biol. Bio- tion of cellulose. Z. Pflanzenernaehr. Bodenkd. 7:171–177.
chem. 25(10):1317–1329. Stute, J.K., and J.L. Posner. 1995. Synchrony between legume N re-
Griffiths, B.S., M.M.I. Van Vuuren, and D. Robinson. 1994. Microbial lease and corn demand in the Upper Midwest. Agron. J. 87:
grazer population in a
N labelled organic residue and the uptake 1063–1069.
of residue N by wheat. Eur. J. Agron. 3(4):321–325. Swift, M.J. (ed.) 1987. Tropical soil biology and fertility: Interregional
Harris, G.H., O.B. Hesterman, E.A. Paul, S.E. Peters, and R.R. Janke. research planning workshop. Spec. Issue 13. IUBS, Biology Int.,
1994. Fate of legume and fertilizer nitrogen-15 in a long-term crop- Paris.
ping systems experiment. Agron. J. 86:910–915. Tho
¨nnissen Michel, C. 1996. Nitrogen fertilizer substitution for tomato
He, X.T., F.J. Stevenson, R.L. Mulvaney, and K.R. Kelly. 1988. Incor- by legume green manures in tropical vegetable production systems.
poration of newly immobilized
N into stable organic forms in soil. Thesis ETHZ No. 11626. Swiss Fed. Inst. of Technol., Zurich.
Soil Biol. Biochem. 20(1):75–81. Varco, J.J., W.W. Frye, M.S. Smith, and C.T. MacKown. 1989. Tillage
Hunt, H.W. 1977. A simulation model for decomposition in grasslands. effects on nitrogen recovery by corn from a nitrogen-15 labeled
Ecology 58:469–484. legume cover crop. Soil Sci. Soc. Am. J. 53:822–827.
Janzen, H.H., and S.M. McGinn. 1991. Volatile loss of nitrogen during Wieder, R.K., and G.E. Lang. 1982. A critique of the analytical meth-
decomposition of legume green manure. Soil Biol. Biochem. 23(3): ods used in examining decomposition data obtained from litter
291–297. bags. Ecology 63(6):1636–1642.
Ladd, J.N., M. Amato, R.B. Jackson, and J.H. Butler. 1983. Utilization Wilson, D.O., and W.L. Hargrove. 1986. Release of nitrogen from
by wheat crops of nitrogen from legume residues decomposing in crimson clover residue under two tillage systems. Soil Sci. Soc.
Am. J. 50:1251–1254.soils in the field. Soil Biol. Biochem. 15(3):231–238.
... The variables percentage of decomposition and mineralized N of the field experiment, as well as biomass yield, concentration of N (%) and total N in the wheat biomass harvested in the experiment in pots, were subjected to an analysis of variance and comparison of averages using the Tukey test (0.05), the statistical program Statgraphics Centurión XVII (Statgraphics, 2014) was used. La rápida descomposición del AV en términos de pérdida de biomasa en las primeras semanas de incubación, así como una pérdida de peso lenta y gradual hasta el final del periodo de incubación es consistente con lo reportado por Thönnissen et al. (2000), los cuales mencionan pérdidas de peso del 30 al 70 % en Glicyne max e Indigofera tinctoria después de cinco semanas de incubación. En Brasil las especies Arachis pintoi, Calopogonium muconoides, Stizilobium aterrimum y Stylosantes guianensis fueron evaluadas como AV en plantaciones de café y se reportaron valores de pérdida samplings, the AV weight losses in the Regosol soil varied from 78.93 % in the flowering stage to 84.02 % in the vegetative stage. ...
... The rapid decomposition of VA in terms of biomass loss in the first weeks of incubation, as well as a slow and gradual weight loss until the end of the incubation period is consistent with that reported by Thönnissen et al. (2000), who mention weight losses of 30 to 70 % in Glicyne max and Indigofera tinctoria after five weeks of incubation. In Brazil, the species Arachis pintoi, Calopogonium muconoides, Stizilobium térimum and Stylosdamientos guianensis were evaluated as VA in coffee plantations and biomass loss values of 30 to 60 % were reported in the first 30 days (Matos et al., 2011). ...
... On the other hand, it is possible that the initial chemical composition of the VA, regardless of the phenological stage, was another factor that favored the rapid decomposition and mineralization of N, generally materials with a low C:N ratio and low lignin content (typical of many legumes) tend to decompose and mineralize faster than some organic substrates with high levels (Brunetto et al., 2011), therefore, high N contents in the C:N ratio and lignin limit the growth of decomposing microorganisms, for which is common the presence of recalcitrant compounds whose molecules present bonds more resistant to the degradation of organic materials (Brunetto et al., 2011;Odhiambo, 2010). In this regard, Thönnissen et al. (2000) mentioned that the weight loss pattern is consistent with previous assumptions that residues contain labile and recalcitrant fractions, which have different degrees of resistance to degradation microbial action. In this a descomponerse y mineralizarse más rápido que algunos sustratos orgánicos con niveles altos (Brunetto et al., 2011), por lo tanto, altos contenidos de N en la relación C:N y lignina limitan el crecimiento de los microorganismos descomponedores, por lo cual es común la presencia de compuestos recalcitrantes cuyas moléculas presentan enlaces más resistentes a la degradación de los materiales orgánicos (Brunetto et al., 2011;(Odhiambo, 2010). ...
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The environmental impact generated by agriculture with excessive use of fertilizers has led to the search for alternatives to improve soil fertility. This study aimed to evaluate the potential of Lupinus exaltatus in terms of decomposition and mineralization of nitrogen (N) when incorporated into the soil as green manure (GM) and its effect on the growth of Triticum aestivum L. seedlings. Litter bags were used, with a total of 216 nylon bags (10 × 5 cm), in each bag were placed 5 g dry base of GM in the vegetative stage and flowering. Subsequently, the GM bags were placed separately Vertisol and Regosol soil at a depth of 5 cm; and every three weeks until the end of the incubation, three bags were recovered per treatment. For evaluation of the effect GM on T. aestivum growth experiment was established in pots with soil Regosol, it consisted of incorporating 50 and 34 g dry base of the GM (equivalent to 10 and 15 t.ha-1). The GM in the vegetative stage lost an average of 83,52 % of its initial weight, while in flowering the loss was 76,49 %, the mineralized N was higher in Regosol soil than in Vertisol with 74,02 % and 70,58 % respectively. The wheat seedlings presented 30 % more dry matter and N with GM than the control treatment. L. exaltatus had a rapid decomposition and mineralization of N in the first stages of incubation.
... Several species of leguminous plants, i.e., Arachis pintoi, Calopogonium mucunoides, Stylosanthes guianensis, and Stizolobium aterrimus, have a great capacity to produce high amounts of biomass and accumulate high nutrient concentrations (Matos et al. 2008), after residue decomposition, it becomes available to crops. Residue quality and quantity decide the decomposition and nutrient release in the ecosystem of higher altitudes; however, residue is defined in relation to its chemical and biochemical composition (Matos et al. 2008) because of chemical and biochemical composition of residue influence the activity of decomposer communities (Thonnissen et al. 2000). Nutrient contents in plant materials are correlated with decomposition rates; if there is high nutrient content plant material, then there will be high decomposition and nutrient release, and it also induces microbial growth and activity (Cobo et al. 2002;Thonnissen et al. 2000). ...
... Residue quality and quantity decide the decomposition and nutrient release in the ecosystem of higher altitudes; however, residue is defined in relation to its chemical and biochemical composition (Matos et al. 2008) because of chemical and biochemical composition of residue influence the activity of decomposer communities (Thonnissen et al. 2000). Nutrient contents in plant materials are correlated with decomposition rates; if there is high nutrient content plant material, then there will be high decomposition and nutrient release, and it also induces microbial growth and activity (Cobo et al. 2002;Thonnissen et al. 2000). ...
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Healthy soil ecosystem is a prerequisite for better agricultural productivity, which is governed by various local abiotic and biotic factors. Agricultural system at higher altitudes has unique characteristics and is entirely distinct from that at the lower altitude. The abiotic and biotic factors are the drivers of the soil ecosystem processes and functioning which improve plant growth and development, ultimately productivity. The key abiotic factors at higher altitudes consist of temperature, precipitation/rainfall pattern, wind profile, light intensity and duration, physiographic, etc.; and the key biotic factors are soil fauna and flora (microbes, fungi, protozoa, nematodes, etc.) influencing the soil ecosystem and agricultural productivity. These major biotic and abiotic factors interact with each other and influence the local agricultural system at higher altitude. The abiotic factors manipulate the microenvironment of soil microbial communities which eventually influence the activity of soil fauna and flora in the soil ecosystem that determines plant growth, resulting in agricultural productivity. Due to the course of these factors, decomposition pattern and rate in the ecosystem are altered, and the decomposition pattern/rate of crop residue has released the nutrients in the soil ecosystem which further are utilized by soil microbes and plants as the source of energy, resulting in increased soil productivity. In this perspective, this chapter explores the mystery of interrelationship of soil ecosystem functioning and various factors that govern the systematic agricultural productivity.
... There was a slight tendency for greater loss of weight in Between weeks 6 and 12, the loss of mass by both species was more gradual, and these losses were minimal between 15 and 18 weeks, probably due to the low recorded rainfall and the accumulation of recalcitrant components, such as lignin and cellulose, which protect cell walls from attack by microorganisms (Thönnissen et al., 2000). In general, our results on the fast initial decomposition of found rapid decomposition (average 30-45% of weight lost after 1 month). ...
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The amount of biomass produced by various native species of genus Lupinus (L.) growing in Mexico ranges from 2.9-8.2 Mg/ha of dry matter, which can add up to 200 kg/ha of N to soil as green manure. However, information is scarce on the decomposition and mineralisation this biomass in the soil. The above-ground decomposition and N mineralisation of Lupinus mexicanus Cerv. ex Lag. and Lupinus rotundiflorus M.E. Jones species from Mexico using fine-mesh litter bags was evaluated. Litter bags containing 5 g of above-ground air-dried biomass at the vegetative and flowering stages were buried at a depth of 20 cm. Were dug up every 3 weeks over the course of 4 months, dried and re-weighed to determine the lost mass and total N by the Kjeldahl method. The largest decrease in residue mass occurred during the first 3 weeks of incubation. However, the lost mass was higher in younger green manure (75 days old) than in older plants (85 days old) after 18 weeks of exposure in the field. It was found that 60-75% of the total N in the plant material was released in the first 6 weeks. In L. rotundiflorus green manure, it was found that 79.14% of the initial N in the vegetative stage and 77.6% of N in the flowering stage was released 18 weeks after litter bag installation, whereas L. mexicanus were 74.6% and 74.7%, respectively. It was found that both decomposition and N mineralisation occurred quickly in the green manures evaluated.
... Este efecto es considerado real si el desarrollo de las raíces y la eficiencia en la absorción fue mayor como resultado de la adición de una fuente nitrogenada, demostrándose la estrecha relación existente entre la mineralización del nitrógeno y su absorción por las plantas (Thönnissen et al. 2000). ...
... Overall, our study showed that the effects of GM residues containing Phi depended on soil type and GM species. Although lower decomposition rates of GM residues were expected in the clay soil (Midmore et al., 2000), no differences between soil types were observed. In fact, decomposition rate of GM residues was mainly influenced by the GM species (Table S1) likely as a result of physico-chemical properties of GM litter (Halvorson and Smith, 1995). ...
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Recycling phosphorus (P) is crucial to meet future P demand for crop production. We investigated the possibility to use calcium phosphite (Ca-Phi) waste, an industrial by-product, as P fertilizer following the oxidation of phosphite (Phi) to phosphate (Pi) during green manure (GM) cropping in order to target P nutrition of subsequent maize crop. In a greenhouse experiment, four GM crops were fertilized (38 kg P ha-1) with Ca-Phi, triple super phosphate (TSP) or without P (Control) in sandy and clay soils. The harvested GM biomass (containing Phi after Ca-Phi fertilization) was incorporated into the soil before maize sowing. Incorporation of GM residues containing Phi slowed down organic carbon mineralization in clay soil and mass loss of GM residues in sandy soil. Microbial enzymatic activities were affected by Ca-Phi and TSP fertilization at the end of maize crop whereas microbial biomass was similarly influenced by TSP and Ca-Phi in both soils. Compared to Control, Ca-Phi and TSP increased similarly the available P (up to 5 mg P kg-1) in sandy soil, whereas in clay soil available P increased only with Ca-Phi (up to 6 mg P kg-1), indicating that Phi oxidation occurred during GM crops. Accordingly, no Phi was found in maize biomass. However, P fertilization did not enhance aboveground maize productivity and P export, likely because soil available P was not limiting. Overall, our results indicate that Ca-Phi might be used as P source for a subsequent crop since Phi undergoes oxidation during the preliminary GM growth.
... In the literature, the results concerning the effects of residues on crop productivity are, however, divergent. Some studies have shown the immediate positive effect of the addition of crop residues on crop productivity [30,36,37]. However, many studies have shown that in the short term, the effects of the contribution of crop residues on crop productivity are low or even negative [38,39]. ...
... Previous 15 N-labelled soybean residue studies in the tropics have indicated the peak of N release occurs during 2-8 weeks after application, depending on residue placement, moisture and temperature (Thönnissen et al. 2000), and the N losses observed in our study over a 16-week period in the subtropics suggest similarly rapid mineralisation of N in soybean residues. Owing to the variation in %N in shoots (Table 1), the C : N in the three fields used for the isotope study ranged from 13 : 1 (field 9) to 16 : 1 (field 5), compared to 9 : 1 for the 15 N-labelled residue applied. ...
Legumes including soybeans (Glycine max L.) can provide substantial nitrogen (N) inputs into cropping systems when grown as a part of a rotation. However, in the wet subtropics where land is fallowed for 4–6 months after soybean crops before planting of sugarcane (Saccharum L. spp. hybrids), climatic conditions over winter can be conducive to rapid mineralisation of N from residues with consequent N losses through nitrate leaching or denitrification processes. Using 15N natural abundance methodology, we estimated N2 fixation in 12 summer-grown soybean crops in the Australian wet subtropics, and tracked the fate of soybean residue-N from brown manure crops (residue from plants at late pod-filling left on the soil surface) using 15N-labelled residue in three of these fields over the winter fallow period. Disregarding two poor crops, N2 fixation ranged from 100–290 kg N ha–1 in shoots at mid pod-filling, equating to 170–468 kg N ha–1 including estimated root N contributions. Following the winter fallow, 61 and 68% of soybean residue-N was recovered in clay and peat soils respectively, to 0.9 m depth at one location (Coraki) but only 55% of residue-N could be accounted for to 0.9 m depth in a sandy soil at another location (Ballina). In addition, around 20% of the recovered 15N at this site was located at 0.3–0.6 m depth in the soil profile. Our results indicate that substantial loss of soybean residue-N can occur during winter fallows in the wet subtropics, suggesting that winter cover crops may be necessary to retain N in fields and minimise losses to the environment.
... During mineralization of organic matter, a rapid release of K occurred and followed by slower releases of N, P and Ca [47]. However, the release of N, K and Ca is usually greater in legume litter due to tenderness of legume leaves compared to the slow release from grasses due to their higher lignification [48]. ...
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Purpose: An experiment was conducted at Field Laboratory of the Department of Crop Botany, Bangladesh Agricultural University during April to July 2018 to compare the biomass yield potential, decomposition and nutrients release pattern of different dhaincha genotypes. Research Method: Six dhaincha accessions from three Sesbania species, viz. S. bispinosa (accession #05, 71, 77 and 109), S. cannabina (accession #28) and S. sesbsan (accession #81), were used as experimental materials. Dhaincha was cultivated with standard cultivation procedure following a randomized complete block design with three replications and incorporated with soil at 60 days after sowing. Findings: There are wide variations in biomass yield, crude fibre and crude protein among the accessions. The amount of crude fibre may be used as a descriptor of taxonomic importance. Accession #28 (S. cannabina) produced a significantly higher amount of crude fibre compared to other accessions. Soil organic matter (SOM) and nutrient elements availability increased with the period of time and reached to a peak at 50 days after biomass incorporation (DAI) except K and S. The highest amount of SOM and N was recorded in accession #71 and the lowest in accession #81. The maximum amount of phosphorus and potassium was added by accession #05 and the minimum phosphorus and potassium by accession #28 and #81, respectively. The greatest amount of sulfur showed 5.25 ppm in accession #05 at 20 DAI and the smallest value 2.22 ppm in accession #28 at 60 DAI. Originality/value: It is evident from results that accession #71 can be recommended for cultivation in the farmer’s field for higher biomass yield and the maximum amount of nutrients release.
Green manuring is an arable-farming practice in which undecomposed green material is incorporated (in situ/harvested elsewhere) into soil in order to increase productivity of subsequent crops. Green manure crop is to be turned into the soil at the point of flowering, i.e., about 7–8 weeks from sowing in most crops. The continuous use of green manures enhances the organic matter content and also supplements the nutrient pool of the soil which ultimately improves the soil physical, chemical and biological properties and also suppresses the weeds. It provides nutrient-rich organic matter for the soil microorganisms which easily converts organically bound nutrients in plant residues to easily available nutrient form to the crop. The portion of green manure nitrogen available to a succeeding crop is usually about 40–60% of the total amount contained in the legume and large amounts of legume N retained in soil mostly in organic forms. However, beneficial effects of green manure on succeeding crops depend largely on residue quantity and quality, soil type, soil fertility, soil acidity, biological activity, soil moisture, and temperature.
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The usual methods proposed to predict net mineral N available to crops, i.e. chemical and biological methods and long-term incubations, are analyzed. The failure in the extrapolation of laboratory data and models to predict true N fluxes in situ mainly results from gross mineralization and immobilization. The processes determining gross fluxes are discussed. Many methodological and theoretical problems are posed by the measurements of true N fluxes under field conditions. First estimations of these fluxes in different crop systems show that the net mineralization rate results from high rates of gross mineralization and immobilization.
The aim of this study was to determine the extent and timing of mineral N release from a localized source of decomposing residue (hotspot) and its subsequent uptake by a growing plant, in relation to changes in the populations of microbial-feeding nematodes and protozoa. Dried and ground ryegrass labelled with 15N was used to create a hotspot at a depth of 30 cm in a column of clay-loam soil. Wheat plants grown in the columns were harvested after 10, 16, 22, 28 and 34 days and analyzed for total N and 15N content, along with simultaneous measurements of soil mineral N and microfauna. There was a rapid increase in microfauna and mineral N, indicating rapid mineralization activity. A total of 25 per cent of the N initially in the residue was present in the wheat plants after 34 days. The pattern of residue N uptake was sigmoidal, with 62 per cent of residue N uptake occurring between days 16-22. The importance of synchronization between mineralization and plant N uptake is discussed.
A model has been developed to simulate the dynamics of decomposers and substrates in grasslands. Substrates represented are humic material, feces, and dead plant and animal remains. Except for humic material, substrates are further divided into a rapidly and a slowly decomposing fraction. The proportion of rapidly decomposing material in a substrate is predicted from its initial nitrogen content. The belowground portion of the system is divided into layers because temperature and soil water, the most important driving variables for the model, vary with depth. Decomposition rates are predicted from temperature, water tension, and inorganic nitrogen concentration. Taxonomic groups of decomposers are not distinguished, but a distinction is made between active and inactive states, which differ in both respiration and death rates and in that only active decomposers assimilate substrate. The model’s predictions compare favorably to data on carbon-dioxide evolution and to litter-bag experiments, but not to ATP estimates of active microbial bioass. The model indicates a profound influence of soil depth on decomposition rates and on decomposer biomass dynamics, growth yield, and secondary productivity.
The effect of available C and N on the rate of wheat (Triticum aestivum L.) straw decomposition by microorganisms was determined using electrolytic respirometers under laboratory conditions. Three lots of spring wheat straw containing 1.13, 0.79 and 0.18% N were used. Cold-water soluble C and N were leached from the wheat straw and the respiration from the leached and non-leached straws (1.5 g of each), with and without added N, were compared in a sand system for 881 h. The fraction of soluble C declined as straw N content declined (total soluble C was 14.0, 11.4 and 8.9%, respectively, for the three straws). The fraction of soluble N declined as straw N content declined, but the proportion of total N that was soluble varied with initial straw N content. We postulated from decomposition data for the various treatments that the amount of microbial biomass produced and the overall rate of wheat straw decomposition in the early stages is largely dependent on the size of the soluble C pool and an intermediately-available C pool that is not cold-water soluble but decomposes within the first few days of decay. Our results from this study imply that the amount of N immobilized during wheat straw decomposition is dependent on the amount of available C from both the primary and secondary pools present in the straw. The data also suggest that the soluble C pool and the intermediately-available C pool were metabolized simultaneously.
Decomposition studies were conducted on corn (Zea mays L. ), wheat (Triticum aestivum L. ), and soybean (Glycine max L. ) residue with emphasis on quantitative determination of the microbial populations colonizing the residues and identification of the predominant fungi isolated from the residues. The study was conducted over a 2-yr period in a Mexico silt loam (Udollic Ochraqualf) at Sanborn Field in Columbia, MO. Plant residues were placed in a porous net and buried in the field. At intervals these sacks were exhumed, washed, and the washings were plated on rose bengal and soil extract agars. The residue was dried and weighed to determine decomposition rates. The predominant fungi were isolated and identified. Microbial determinations were conducted on soil samples taken from the same plots.
Determined N release from Trifolium incarnatum residue under no-tillage and conventional tillage conditions. Under humid, subtropical conditions, release of N from both surface and buried residue from winter legumes is sufficiently rapid to be of significant benefit to the summer crop.-from Authors