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1.
The benefit of planted fallow with legume cover crops may be limited on P deficient soil. A trial was conducted at two P deficient
sites in northern Nigeria to test the hypothesis that application of P to legume cover crop fallow can substitute for N application
to subsequent maize. Mainplots consisted of leguminous fallows followed by unfertilized maize, or native (mostly grass) fallows
followed by maize with 0 or 40 kg N ha−1 (Kaduna) and 0, 30 or 60 kg N ha−1 (Bauchi). Three rates of P (0, 9, and 18 kg ha−1) were applied to fallow sub-plots as single superphosphate. In the first year, dry matter accumulation of lablab (Lablab purpureus) responded to P application, while mucuna (Mucuna cochinchinensis) dry matter did not. Lablab mulch dry matter during the dry season was significantly increased by previous season P application
while mucuna was not. Previous fallow vegetation was a significant factor for maize growth in the second year but the interaction
with P applied to the fallow was not significant at P < 0.05. Substantial and similar yield increases were achieved with application of N fertilizer to maize and from application
of 9 kg P ha−1 to previous lablab. Depending on local economic circumstances, a good use of expensive inorganic fertilizer might be to apply
P sources to cover crop legumes to profit from additional N benefits as well as residual effects of applied P.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
Regis Chikowo Paul Mapfumo Peter A. Leffelaar Ken E. Giller 《Nutrient Cycling in Agroecosystems》2006,76(2-3):219-231
The release of mineral-N in soil from plant residues is regulated by their ‘quality’ or chemical composition. Legume materials
used by farmers in southern Africa are often in the form of litter with N concentration <2%. We investigated the decomposition
of Sesbania sesban and Acacia angustissima litter in the field using litterbags, and N mineralization of a range of legume materials using a leaching tube incubation
method in the laboratory. The mass loss of the litter could be described using a modified exponential decay model: Y = (Y
0−Q)e−kt
+ Q. The relative decomposition constants for Sesbania and Acacia litter were 0.053 and 0.039 d−1, respectively. The % N mineralized from fresh Sesbania prunings was 55% compared with only 27% for the Sesbania litter after 120 days of incubation under leaching conditions. During the same period, fresh prunings of Acacia released only 12% of the added N while Acacia litter released 9%. Despite the large differences in N concentration between Acacia prunings and its litter, the total mineralized N was similar, as mineralization from prunings was depressed by the highly
active polyphenols. While N supply may be poor, these slow decomposing litter materials are potentially useful for maintaining
soil organic matter in smallholder farms. In two field experiments with contrasting soil texture, Sesbania, Acacia and Cajanus produced large amounts of biomass (>5 Mg ha−1) and improved N cycling significantly (>150 kg N ha−1) on the clay loam soil, but adapted poorly on the sandier soil. There was a rapid N accumulation in the topsoil at the beginning
of the rains in plots where large amounts of Sesbania or Acacia biomass had been incorporated. Despite the wide differences in resource quality between these two, there was virtually no
difference in N availability in the field as this was, among other factors, confounded by the quantity of N added. A substantial
amount of the nitrate was leached to greater than 0.4 m depth within a three-week period. Also, the incidence of pests in
the first season, and drought in the second season resulted in poor nitrogen use efficiency. Our measurements of gaseous N
losses in the field confirmed that N2O emissions were <0.5 kg N ha−1. As we had measurements of all major N flows, we were able to construct overall N budgets for the improved fallow – maize
rotation systems. These budgets indicated that, in a normal rainfall season with no major pest problems, reducing nitrate
leaching would be the single largest challenge to increased N recovery of added organic N in the light textured soils. 相似文献
3.
In degraded soils, establishment of soil-improving legumes can be problematic and requires investment of labour and other
resources. We investigated various aspects of managing herbaceous legumes in farmers’ fields in Bukoba District, Tanzania.
Biomass and N accumulation by Crotalaria grahamiana was 1.1 Mg ha−1 and 34 kg N ha−1 when established without farmyard manure (FYM) and 3.0 Mg ha−1 and 95 kg N ha−1 when established with 2 Mg FYM ha−1, and incorporation of the biomass gave an increment of 700 kg ha−1 of grain in the subsequent maize crop. Maize grain yield at different application rates of Tephrosia candida residues ranged from 1.4 to 3.3 Mg ha−1 and from 2.0 to 2.8 Mg ha−1 in the high and low rainfall zone, respectively. Application of tephrosia biomass at a rate of 2 Mg ha−1 had no significant effect on maize yield whereas rates of 4, 6 and 8 Mg ha−1 gave comparable yields. Apparent N recovery efficiencies at all rates of tephrosia residues were maximally 27 and 13% for
the high and low rainfall zones, respectively. Mulching with Mucuna pruriens suppressed weeds by 49 and 68% and increased maize yield by 57 and 103% compared with the weedy fallow in the respective
zones. Incorporated residues had a weaker effect on suppressing weeds and poor labour productivity (2 l and 36 kg grain person-day−1) compared with mulched residues (32 and 52 kg grain person-day−1) in the high and low rainfall zone, respectively. These results indicate that if well managed, legume residues have the potential
to increase yields of subsequent maize crops on degraded soils. 相似文献
4.
Gilbert C. Sigua Samuel W. Coleman Joseph Albano Mimi Williams 《Nutrient Cycling in Agroecosystems》2011,89(1):59-70
Characterizing and assessing spatial distribution of soil phosphorus and herbage mass in relation to landscape properties,
land use, or landscape positions is important for understanding how pasture sustainability can be managed and improved properly.
Our reason for conducting this study was to determine the effects of different slope aspects and slope positions on spatial
distribution of soil phosphorus and herbage mass in subtropical pastures. Soil and forage samples were collected from contiguous
south-, north-, east-, and west-facing slopes across different landscape positions (top slope, middle slope, and bottom slope)
in 100 ha of bahiagrass (Paspalum notatum)-based pastures from 2003 to 2006 in subtropical region of southeastern USA. Averaged across years, soils on the north-facing
slope contained the greatest amount of soil phosphorus (12.4 ± 2.7 mg kg−1) when compared with other slope aspects. Slope aspect may be acting as an important topographic factor influencing local
site microclimate mainly because it determines the amount of solar radiation received. The greatest herbage mass (averaged
across year) of 2,967 ± 980 kg ha−1 and the highest phosphorus accumulation of 7.7 ± 3.0 kg ha−1 for bahiagrass were from the top slope position. There was a significant (P ≤ 0.05) decrease in the average herbage mass and phosphorus accumulation with decreasing slope (top to middle slope). Between
the top slope and the bottom slope, herbage mass declined from 2,967 ± 980 to 1,805 ± 370 kg ha−1 while phosphorus accumulation was reduced by approximately 40% (7.7–4.6 kg ha−1). Results of our study may increase awareness on how the arrangement of food, water, and shelter and their interactions with
topographic and landscape features can significantly influence the movement of animals and utilization of different pastures’
resources. While our study supports our hypothesis that slope aspect and slope position could be of relative importance in
controlling spatial distribution of soil phosphorus and herbage mass, broad knowledge of cattle movement in pasture situations
is as critical to understanding their impact on agro-ecosystems. 相似文献
5.
Soil organic carbon dynamics of improved fallow-maize rotation systems under conventional and no-tillage in Central Zimbabwe 总被引:1,自引:0,他引:1
George Nyamadzawo Regis Chikowo Philip Nyamugafata Justice Nyamangara Ken E. Giller 《Nutrient Cycling in Agroecosystems》2008,81(1):85-93
Fallowing increases soil organic carbon (SOC) during the fallowing phase. However, this benefit is lost quickly during the
cropping phase. The objective of this study was to evaluate SOC dynamics of an improved fallow-maize rotation under no-tillage
(NT) and conventional tillage (CT) from time of fallow termination, through the next two cropping seasons. The treatments
studied were improved fallows of Acacia angustissima (A. angustissima) and Sesbania sesban (S. sesban), natural fallow and continuous maize. Our hypothesis is that fallowing maintained higher SOC and lower soil bulk densities
through the cropping phase when compared with continuous maize system and that NT maintained higher SOC when compared with
CT. Soil organic carbon was significantly greater under fallows than under continuous maize from fallow termination to the
end of the second cropping season. Soil organic carbon for the 0–5 cm depths was 11.0, 10.0, 9.4 and 6.6 g kg−1 for A. angustissima, S. sesban, natural fallow and continuous maize, respectively at fallow termination. After two cropping seasons SOC for the same depth
was 8.0, 7.0, 6.1, 5.9 g kg−1 under CT and 9.1, 9.0, 8.0, 6.0 g kg−1 under NT for A. angustissima, S. sesban, natural fallow and continuous maize, respectively. Total SOC stocks were also higher under fallows when compared with continuous
maize at fallow termination and after two cropping seasons. Soil bulk densities were lower under fallows when compared with
continuous maize during the period of study. We concluded that fallows maintained greater SOC and NT sequestered more SOC
than CT. Acacia angustissima was the better tree legume fallow for SOC sequestration when compared with S. sesban or natural fallow because it maintained higher SOC and lower bulk densities after two seasons of maize cropping. 相似文献
6.
Samuel Adjei-Nsiah Thom W. Kuyper Cees Leeuwis Mark K. Abekoe Joseph Cobbinah Owuraku Sakyi-Dawson Ken E. Giller 《Nutrient Cycling in Agroecosystems》2008,80(3):199-209
Cowpea–maize rotations form an important component of the farming systems of smallholder farmers in the forest/savannah transitional
agro-ecological zone of Ghana. We evaluated five cowpea varieties for grain yield, N2-fixation, biomass production, and contribution to productivity of subsequent maize grown in rotation. We further analyzed
the interrelationship between these technical dimensions and the social acceptability of these cowpea varieties for farmers.
Cowpea grain yield ranged between 1.1 and 1.4 t ha−1 with no significant yield differences among the different varieties. Using the 15N natural abundance technique, the average proportion of N2 fixed ranged between 61% for Ayiyi and 77% for Legon prolific. This resulted in average amounts of N2 fixed in above-ground biomass ranging between 32 and 67 kg N ha−1, respectively. Variation in estimates due to differences in δ15N among reference plants were larger than differences between cowpea varieties. The amount of soil-derived N ranged from 15
to 20 kg N ha−1. The above-ground net N contribution of the cowpea varieties to the soil (after adjusting for N export in grains) was highest
for Legon Prolific (31 kg N ha−1) due to high N2-fixation and high leaf biomass production. Maize grain yield after cowpea without application of mineral N fertilizer ranged
between 0.4 t ha−1 with maize after maize to 1.5 t ha−1 with Legon Prolific. The N fertilizer equivalence values for the cowpea varieties ranged between 18 and 60 kg N ha−1. IT810D-1010 was ranked by the farmers as the most preferred cowpea variety due to its white seed type, short-duration, ease
of harvesting and good market value. Despite the high leaf biomass production and high amount of N2 fixed by Legon Prolific, it was generally the least preferred variety due to lower market price, late maturity, least potential
cash income (due to the red mottled seed type) and difficulty in harvesting. Although farmers recognized the contribution
of cowpea to soil fertility and yields of subsequent maize, they did not consider this as an important criterion for varietal
selection. Soil fertility improvement must be considered as an additional benefit rather than a direct selection criterion
when designing more sustainable smallholder farming systems. 相似文献
7.
Soil nitrate-N levels required for high yield maize production in the North China Plain 总被引:4,自引:0,他引:4
Zhenling Cui Fusuo Zhang Yuxin Miao Qinping Sun Fei Li Xinping Chen Junliang Li Youliang Ye Zhiping Yang Qiang Zhang Chunsheng Liu 《Nutrient Cycling in Agroecosystems》2008,82(2):187-196
High profile nitrate-nitrogen (N) accumulation has caused a series of problems, including low N use efficiency and environmental
contamination in intensive agricultural systems. The key objective of this study was to evaluate summer maize (Zea mays L.) yield and N uptake response to soil nitrate-N accumulation, and determine soil nitrate-N levels to meet N demand of high
yield maize production in the North China Plain (NCP). A total of 1,883 farmers’ fields were investigated and data from 458
no-N plots were analyzed in eight key maize production regions of the NCP from 2000 to 2005. High nitrate-N accumulation (≥172 kg N ha−1) was observed in the top (0–90 cm) and deep (90–180 cm) soil layer with farmers’ N practice during maize growing season.
Across all 458 no-N plots, maize grain yield and N uptake response to initial soil nitrate-N content could be simulated by
a linear plus plateau model, and calculated minimal pre-planting soil nitrate-N content for maximum grain yield and N uptake
was 180 and 186 kg N ha−1, respectively, under no-N application conditions. Economically optimum N rate (EONR) decreased linearly with increasing pre-planting
soil nitrate-N content (r
2 = 0.894), and 1 kg soil nitrate-N ha−1 was equivalent to 1.23 kg fertilizer-N ha−1 for maize production. Residual soil nitrate-N content after maize harvest increased exponentially with increasing N fertilizer
rate (P < 0.001), and average residual soil nitrate-N content at the EONR was 87 kg N ha−1 with a range from 66 to 118 kg N ha−1. We conclude that soil nitrate-N content in the top 90 cm of the soil profile should be maintained within the range of 87–180 kg N ha−1 for high yield maize production. The upper limit of these levels would be reduce if N fertilizer was applied during maize
growing season. 相似文献
8.
Florence Mtambanengwe Paul Mapfumo Bernard Vanlauwe 《Nutrient Cycling in Agroecosystems》2006,76(2-3):271-284
Major challenges for combined use of organic and mineral nutrient sources in smallholder agriculture include variable type
and quality of the resources, their limited availability, timing of their relative application and the proportions at which
the two should be combined. Short-term nutrient supply capacity of five different quality organic resources ranging from high
to low quality, namely Crotalaria juncea, Calliandra calothyrsus, cattle manure, maize stover and Pinus patula sawdust were tested in the field using maize as a test crop. The study was conducted on two contrasting soil types at Makoholi
and Domboshawa, which fall under different agro-ecological regions of Zimbabwe. Makoholi is a semi-arid area (<650 mm yr−1) with predominantly coarse sandy soils containing approximately 90 g kg−1 clay while Domboshawa (>750 mm yr−1) soils are sandy-clay loams with 220 g kg−1 clay. Each organic resource treatment was applied at low (2.5 t C ha−1) and high (7.5 t C ha−1) biomass rates at each site. Each plot was sub-divided into two with one half receiving 120 kg N ha−1 against zero in the other. At Makoholi, there was a nine-fold increase in maize grain yield under high application rates
of C. juncea over the unfertilized control, which yielded only 0.4 t ha−1. Combinations of mineral N fertilizer with the leguminous resources and manure resulted in between 24% and 104% increase
in grain yield against sole fertilizer, implying an increased nutrient recovery by maize under organic–mineral combinations.
Maize biomass measured at 2 weeks after crop emergence already showed treatment differences, with biomass yields increasing
linearly with soil mineral N availability (R
2 = 0.75). This 2-week maize biomass in turn gave a positive linear relationship (R
2 = 0.82) with grain yield suggesting that early season soil mineral N availability largely determined final yield. For low
quality resources of maize stover and sawdust, application of mineral N fertilizer resulted in at least a seven-fold grain
yield increase compared with sole application of the organic resources. Such nutrient combinations resulted in grain harvest
indices of between 44% and 48%, up from a mean of 35% for sole application, suggesting the potential of increasing maize productivity
from combinations of low quality resources with mineral fertilizer under depleted sandy soils. At Domboshawa, grain yields
averaged 7 t ha−1 and did not show any significant treatment differences. This was attributed to relatively high levels of fertility under
the sandy-clay loams during this first year of the trial implementation. Differences in N supply by different resources were
only revealed in grain and stover uptake. Grain N concentration from the high quality leguminous resources averaged 2% against
1.5% from sawdust treatments. We conclude that early season soil mineral N availability is the primary regulatory factor for
maize productivity obtainable under poor sandy soils. Maize biomass at 2 weeks is a potential tool for early season assessment
of potential yields under constrained environments. However, the likely impact on system productivity following repeated application
of high N-containing organic materials on different soil types remains poorly understood. 相似文献
9.
Grain legume rotation benefits to maize in the northern Guinea savanna of Nigeria: fixed-nitrogen versus other rotation effects 总被引:2,自引:0,他引:2
A. A. Yusuf E. N. O. Iwuafor R. C. Abaidoo O. O. Olufajo N. Sanginga 《Nutrient Cycling in Agroecosystems》2009,84(2):129-139
The yield increases often recorded in maize following grain legumes have been attributed to fixed-N and ‘other rotation’ effects,
but these effects have rarely been separated. Field trials were conducted between 2003 and 2005 to measure these effects on
maize following grain legumes in the northern Guinea savanna of Nigeria. Maize was grown on plots previously cultivated to
two genotypes each of soybean (TGx 1448-2E and SAMSOY-2) and cowpea (IT 96D-724 and SAMPEA-7), maize, and natural fallow.
The plots were split into four N fertilizer rates (0, 30, 60 and 90 kg N ha−1) in a split plot design. The total effect was calculated as the yield of maize following a legume minus the yield following
maize, both without added N and the rotation effect was calculated as the difference between rotations at the highest N fertilizer
rate. The legume genotypes fixed between 14 and 51 kg N ha−1 of their total N and had an estimated net N balance ranging from −29.8 to 9.5 kg N ha−1. Positive N balance was obtained only when the nitrogen harvest index was greater than the proportion of N derived from atmosphere.
The results also indicated that the magnitude of the fixed-N and other rotation effects varied widely and were influenced
by the contributions of the grain legumes to the soil N-balance. In general, fixed-N effects ranged from 124 to 279 kg ha−1 while rotation effects ranged between 193 and 513 kg ha−1. On average, maize following legumes had higher grain yield of 1.2 and 1.3-fold compared with maize after fallow or maize
after maize, respectively. 相似文献
10.
P. Ebanyat N. de Ridder A. de Jager R. J. Delve M. A. Bekunda K. E. Giller 《Nutrient Cycling in Agroecosystems》2010,87(2):209-231
Targeting of integrated management practices for smallholder agriculture in sub-Saharan Africa is necessary due to the great
heterogeneity in soil fertility. Experiments were conducted to evaluate the impacts of landscape position and field type on
the biomass yield, N accumulation and N2-fixation by six legumes (cowpea, green gram, groundnut, mucuna, pigeonpea and soyabean) established with and without P during
the short rain season of 2005. Residual effects of the legumes on the productivity of finger millet were assessed for two
subsequent seasons in 2006 in two villages in Pallisa district, eastern Uganda. Legume biomass and N accumulation differed
significantly (P < 0.001) between villages, landscape position, field type and P application rate. Mucuna accumulated the most biomass (4.8–10.9 Mg ha−1) and groundnut the least (1.0–3.4 Mg ha−1) on both good and poor fields in the upper and middle landscape positions. N accumulation and amounts of N2-fixed by the legumes followed a similar trend as biomass, and was increased significantly by application of P. Grain yields
of finger millet were significantly (P < 0.001) higher in the first season after incorporation of legume biomass than in the second season after incorporation.
Finger millet also produced significantly more grain in good fields (0.62–2.15 Mg ha−1) compared with poor fields (0.29–1.49 Mg ha−1) across the two villages. Participatory evaluation of options showed that farmers preferred growing groundnut and were not
interested in growing pigeonpea and mucuna. They preferentially targeted grain legumes to good fields except for mucuna and
pigeonpea which they said they would grow only in poor fields. Benefit-cost ratios indicated that legume-millet rotations
without P application were only profitable on good fields in both villages. We suggest that green gram, cowpea and soyabean
without P can be targeted to good fields on both upper and middle landscape positions in both villages. All legumes grown
with P fertiliser on poor fields provided larger benefits than continuous cropping of millet. 相似文献
11.
Jens M. Vesterager Niels E. Nielsen Henning Høgh-Jensen 《Nutrient Cycling in Agroecosystems》2008,80(1):61-73
Symbiotic N2-fixation, N uptake efficiency, biomass- and crop production of cowpea and maize as affected by P source, sole- and intercropped,
and introduction of break crops were studied on a farmer’s fields in semi-arid Tanzania. Cowpea fixed around 60% of its N
from the atmosphere amounting to 70 kg N ha−1 under sole and 36 kg N ha−1 under intercropping as estimated by the 15N isotope dilution method around peak biomass production. The amount of N2-fixed was 30–40% higher when P was applied as either TSP or MRP whereas cowpea yield were unaffected. Intercropped maize
with 19,000 plant ha−1 accumulated the same amount of N as 38,000 sole cropped maize plants although intercropping reduced the dry matter accumulation
by 25%. The N uptake efficiency of the applied 15N labelled fertiliser was 26%, which equal a total pool of early available plant N of 158 kg N ha−1. Under the N deficient conditions, P application did not increase the grain yield of maize. The LER indicate that sole cropping
required 18% more area than intercropping in order to produce the same grain yield, and 35% more land when LER was based on
N uptakes. Introduction of break crops in the maize systems, more than doubled accumulation of dry matter and N in the grain
compared to continuous maize cropping. During maturation sole crop cowpea shedded leaves containing 41 kg N ha−1. The current findings underline the importance of crop diversity in Sub Saharan Africa agriculture and emphasise the need
for including all residues, including shedded leaves, in nutrient balance studies. 相似文献
12.
Tonny P. Tauro Hatirarami Nezomba Florence Mtambanengwe Paul Mapfumo 《Nutrient Cycling in Agroecosystems》2010,88(1):91-101
Developing soil fertility management options for increasing productivity of staple food crops is a challenge in most parts
of Sub-Saharan Africa, where soils are constrained by nitrogen (N) and phosphorus (P) deficiencies. A study was conducted
to evaluate the response of indigenous legume populations to mineral P application, and subsequently their benefits to maize
yield. Mineral P was applied at 26 kg P ha−1 before legume species were sown in mixtures at 120 seeds m−2 species−1 and left to grow over two rainy seasons (2 years). Application of P increased overall biomass productivity by 20–60% within
6 months, significantly influencing the composition of non-leguminous species. Dinitrogen fixation, as determined by the
N-difference method, was increased by 43–140% although legume biomass productivity was apparently limited by nutrients other
than P and N. Crotalaria pallida and C. ochroleuca accounted for most of the fixed N. Improved N supply increases the abundance of non-leguminous species, particularly Conyza sumatrensis and Ageratum conyzoides. However, abundance of common weed species, Commelina benghalensis, Richardia scabra and Solanum aculeastrum, declined by up to18%. Application of P did not significantly influence productivity of those legume species that reached
maturity within 3 months. There was increased N2-fixation and biomass productivity of indifallows as influenced by specific legume species responding to P application. Compared
with natural (grass) fallows, indigenous legume fallows (indifallows) increased subsequent maize grain yields by ~40%. Overall,
1- and 2-year indifallows gave maize grain yields of >2 and 3 t ha−1, respectively, against <1 t ha−1 under corresponding natural fallows. Two-year indifallows with P notably increased maize yields, but the second year gave
low yields regardless of P treatment. Because of their low P requirement, indigenous legume fallows have potential to stimulate
maize productivity under some of the most nutrient depleted soils. 相似文献
13.
Green leaf manuring with prunings of Leucaena leucocephala is regarded as a useful source of N to plants but the actual substitution of N fertilizer, release and recovery of N as well
as effects on soil fertility are not adequately studied. The present studies investigated the effect of sole and combined
use of Leucaena prunings and urea N fertilizer in different proportions on productivity, profitability, N uptake and balance in maize (Zea mays)–wheat (Triticum aestivum) cropping system at New Delhi during 2002–2003 and 2003–2004. Varying quantities of Leucaena green leaf biomass containing 3.83–4.25% N (18.2–20.5 C:N ratio) were applied to provide 0, 25, 50, 75 and 100% of recommended
N (120 kg ha−1) to both maize and wheat before sowing. In general, direct application of urea N increased the productivity of both crops
more than Leucaena green leaf manure, but the reverse was true for the residual effect of these sources. The productivity of maize increased
progressively with increasing proportions of N through urea fertilizer and was 2.41–2.52 t ha−1 with 60 kg N ha−1 each applied through Leucaena and urea, which was at par with that obtained with 120 kg N ha−1 through urea alone (2.56–2.74 t ha−1). Similarly, wheat yield was also near maximum (4.46–5.11 t ha−1) when equal amounts of N were substituted through Leucaena and urea. Residual effects were obtained on the following crops and were significant when greater quantity of N (>50%) was
substituted through Leucaena. Nitrogen uptake and recovery were also maximum with urea N alone, and N recovery was higher in maize (33.4–42.1%) than in
wheat (27.3–29.8%). However, recovery of residual N in the following crop was more from Leucaena N alone (8.5–10.3%) than from urea fertilizer (1.7–3.8%). Residual soil fertility in terms of organic C and KMnO4 oxidizable N showed improvement with addition of Leucaena prunings, which led to a positive N balance at the end of second cropping cycle. Net returns were considerably higher with
wheat than with maize, and were comparatively lower with greater proportion of Leucaena because of its higher cost. Nonetheless, it was beneficial to apply Leucaena and urea on equal N basis for higher productivity and sustainability of this cereal-based cropping system. 相似文献
14.
Farm product diversification, shade provision and low access to fertilizers often result in the purposeful integration of
upper canopy trees in cocoa (Theobroma cacao) plantations. Subsequent modification to light and soil conditions presumably affects nutrient availability and cocoa tree
nutrition. However, the level of complementarity between species requires investigation to minimize interspecific competition
and improve resource availability. We hypothesized beneficial effects of upper canopy trees on cocoa biomass, light regulation,
soil fertility and nutrient uptake. We measured cocoa standing biomass and soil nutrient stocks under no shade (monoculture)
and under three structurally and functionally distinct shade trees: Albizia zygia (D.C.) Macbr, a nitrogen fixer; Milicia excelsa (Welw.), a native timber species; and Newbouldia laevis (Seem.), a native small stature species. Vector analysis was employed to diagnosis tree nutrition. Cocoa biomass was higher
under shade (22.8 for sole cocoa versus 41.1 Mg ha−1 for cocoa under Milicia), and declined along a spatial gradient from the shade tree (P < 0.05). Percent canopy openness differed between the three shade species (P = 0.0136), although light infiltration was within the optimal range for cocoa production under all three species. Soil exchangeable
K was increased under Newbouldia, while available P decreased and total N status was unaffected under all shade treatments. Nutrient uptake by cocoa increased
under shade (43–80% and 22–45% for N and P, respectively), with K (96–140%) as the most responsive nutrient in these multistrata
systems. Addition of low-density shade trees positively affected cocoa biomass close to the shade tree, however proper management
of upper stratum trees is required for optimum cocoa productivity and sustainability. 相似文献
15.
A. R. Sharma Ratan Singh S. K. Dhyani R. K. Dube 《Nutrient Cycling in Agroecosystems》2010,87(2):187-197
Mulching with vegetative materials is a highly beneficial and widely-investigated agro-technique in rainfed areas but the
adoption of this practice has been constrained due to non-availability of mulch biomass locally. Live mulching with fast-growing
annual green manure legumes like sunnhemp (Crotalaria juncea) or prunings of Leucaena leucocephala grown as hedge rows can be done for moisture conservation as well as nutrient cycling in the maize–wheat cropping system,
which is predominantly followed in the high rainfall sub-mountainous region of north-western India. A field experiment was
conducted at Selakui, Dehradun during 2000–2004 to study the effect of legume mulching, viz. in situ grown sunnhemp and Leucaena prunings, along with varying N levels, viz. 0, 30, 60 and 90 kg N ha−1 (to maize), and 0, 40 and 80 kg N ha−1 (to wheat) on productivity, soil moisture conservation and soil physico-chemical properties. Intercropped sunnhemp added
0.75–1.45 t dry matter and 21.6–41.3 kg N ha−1 at 30–35 days, while Leucaena twigs added 1.89–4.15 t dry matter and 75.2–161.3 kg N ha−1 at 60–65 days of maize growth. Live mulching with sunnhemp or Leucaena biomass improved soil moisture content at maize harvest (+1.15–1.57%) and crop productivity by 6.8–8.8% over no mulching.
Combined use of both the mulching materials was more effective in improving the soil moisture content (+2.08–2.29%) and grain
yield (15.1%) over their single application. Response of maize to N fertilizer application was significant up to 90 kg N ha−1, and it was relatively more pronounced under the mulching treatments. Residual effect of mulching on wheat showed an increase
in yield of 10.2% with sunnhemp or Leucaena, and 27.9% with sunnhemp + Leucaena. There was an improvement in organic C and total N status of soil, and a decrease in bulk density associated with an increase
in infiltration rate due to mulching at the end of 4 cropping cycles. It was concluded that legume mulching is a highly beneficial
practice for enhanced moisture and nutrient conservation, leading to increased productivity and soil health of maize–wheat
cropping system under Doon valley conditions of north-western India. 相似文献
16.
Variations in grain nitrogen removal associated
with management practices in maize production 总被引:1,自引:0,他引:1
Information on N removal by maize (Zea mays L.) grain production is not only required for proper soil N management, but also a prerequisite for environmental risk assessment. The objectives of this field study were to (i) assess the variations of maize grain N removal in relation to weather and agronomic practices, and (ii) determine if a common N removal factor can be used for environment risk assessment with the Ontario N index method. Maize grain samples from four field experiments including treatments of hybrids, rotation systems and fertilizer N levels under different environmental conditions were used to determine nitrogen removal factor (grain N in kg ha−1 divided by grain yield in Mg ha−1, i.e. kg N Mg−1). In general, grain N removal averaged 12.0 kg N Mg−1, which is substantially smaller than 16 kg Mg−1 used in the Ontario N Index model. However, large variations (7.1–16.7 kg N Mg−1) in the N removal factor existed among years, rotation systems, hybrids and level of fertilizer N application. Our data indicate that an index using a constant grain N removal factor may not be representative of different growing conditions, hybrids and fertilizer levels. Hence, care must be taken when using a constant grain N removal factor with the N index approach to assess N overloading for nutrient management legislation purposes. 相似文献
17.
A. Mukuralinda J. S. Tenywa L. Verchot J. Obua S. Namirembe 《Nutrient Cycling in Agroecosystems》2009,84(2):155-166
Phosphorus release from decomposing leaf biomass of Calliandra
calothyrsus Meissner, Tithonia diversifolia Hensley A.Gray and Tephrosia vogelii Hook.f. agroforestry species applied alone or combined with triple super phosphate (TSP) was studied at World Agroforestry
Centre (ICRAF) laboratory for 56 days using an incubation method. The effects of above treatments on maize yield were evaluated
in the field at Rubona, southern province of Rwanda between the years 2001 and 2004. The net cumulative phosphorus (P) mineralised
ranged from 16.2 to 212.2 mg P kg−1. The net P mineralisation rates from green manure, TSP applied alone or combined with green manure decreased in the order
green manure > green manure + TSP > TSP > lime > control. The best plant residues quality for predicting P mineralisation
is total P, C, and C:P & C:N ratios. Relative to the control, leaf biomass combined with TSP resulted in six times higher
maize grain yield at the end of the experiment i.e., from 0.9 to 7.1 t ha−1. In the fourth season, application of Tithonia diversifolia Hensley A.Gray green manure combined with TSP at 50 kg P ha−1 resulted in higher maize yield (25% increase) than TSP and Tithonia diversifolia Hensley A.Gray (9% increase) applied alone at the similar rate. Therefore, application of plant residues and TSP alone might
not be sufficient to meet maize plant P requirements and to achieve the yield potential of maize in the Rubona soils unless
supplemented with mineral fertilisers. 相似文献
18.
Crop productivity and nutrient use efficiency as affected by long-term fertilisation in North China Plain 总被引:3,自引:0,他引:3
Yingchun Wang Enli Wang Daolong Wang Shaomin Huang Yibing Ma Chris J. Smith Ligang Wang 《Nutrient Cycling in Agroecosystems》2010,86(1):105-119
Nutrient inputs into crop production systems through fertilisation have come under increased scrutiny in recent years because
of reduced nutrient use efficiency and increased environmental impact. Fifteen years of experimental data on dynamics of N,
P and K in soil, crop yield and nutrient uptake from nine fertilisation treatments at Zhengzhou, North China Plain, were used
to analyse the contribution of different fertilisation treatments to crop yield, nutrient use efficiency and accumulation
of nutrients in soil. The results showed that both N and P were limiting factors for crop growth. Without additional N and
P fertilisation, only a very low yield level (ca 2 t ha−1 for wheat and 3 t ha−1 for maize) could be maintained. To achieve the potential productivity (i.e. yield level free of water and nutrient stresses)
of wheat (6.9 t ha−1) and maize (8.3 t ha−1), wheat would need, on average, 170 kg N ha−1, 32 kg P ha−1 and 130 kg K ha−1, while maize would need 189 kg N ha−1, 34 kg P ha−1 and 212 kg K ha−1. The N and P demands correspond well to the N and P levels supplied in one of the fertilisation treatments (NPK), while K
deficiency could occur in the future if no crop residues were returned or no extra K was applied. On average under this NPK
treatment, 80% of N and 71% of P could be recovered by the wheat–maize system. Treatments with nutrient inputs higher than
the NPK treatment and treatments without combination of N and P have led to accumulation of N and P in the soil profile. The
input levels of N and P in the NPK treatment are recommended in fertiliser management, with additional K to avoid future soil
K deficiency. 相似文献
19.
B. Ncube J. P. Dimes S. J. Twomlow W. Mupangwa K. E. Giller 《Nutrient Cycling in Agroecosystems》2007,77(1):53-67
Participatory on-farm trials were conducted for three seasons to assess the benefits of small rates of manure and nitrogen
fertilizer on maize grain yield in semi-arid Tsholotsho, Zimbabwe. Two farmer resource groups conducted trials based on available
amounts of manure, 3 t ha−1 (low resource group) and 6 t ha−1 (high resource group). Maize yields varied between 0.15 t ha−1 and 4.28 t ha−1 and both absolute yields and response to manure were strongly related to rainfall received across seasons (P < 0.001). The first two seasons were dry while the third season received above average rainfall. Maize yields within the
seasons were strongly related to N applied (R
2 = 0.77 in season 1, and R
2 = 0.88 and 0.83 in season 3) and other beneficial effects of manure, possibly availability of cations and P. In the 2001–2002
season (total rainfall 478 mm), application of 3 and 6 t ha−1 of manure in combination with N fertilizer increased grain yield by about 0.14 and 0.18 t ha−1, respectively. The trend was similar for the high resource group in 2002–2003 although the season was very dry (334 mm).
In 2003–2004, with good rainfall (672 mm), grain yields were high even for the control plots (average 1.2 and 2.7 t ha−1). Maize yields due to manure applications at 3 and 6 t ha−1 were 1.96 and 3.44 t ha−1, respectively. Application of 8.5 kg N ha−1 increased yields to 2.5 t ha−1 with 3 t ha−1 of manure, and to 4.28 t ha−1 with 6 t ha−1 of manure. In this area farmers do not traditionally use either manure or fertilizer on their crops, but they actively participated
in this research during three consecutive seasons and were positive about using the outcomes of the research in future. The
results showed that there is potential to improve livelihoods of smallholder farmers through the use of small rates of manure
and N under semi-arid conditions. 相似文献
20.
Chun Song Enli Wang Xiaozeng Han Richard Stirzaker 《Nutrient Cycling in Agroecosystems》2011,89(3):363-374
A 19-year field experiment on a Mollisol agroecosystem was carried out to study the productivity of a wheat-maize-soybean
rotation and the changes in soil carbon and nutrient status in response to different fertiliser applications in Northeast
China. The experiment consisted of seven fertiliser treatments: (1) unfertilised control, (2) annual application of P and
K fertilisers, (3) N and K fertilisers, (4) N and P fertilisers, (5) N, P and K fertilisers, (6) N, K and second level P fertilisers,
and (7) N, P and second level K fertilisers. Without fertiliser, the Mollisols could support an average yield of 1.88 t ha−1 for wheat, 3.89 t ha−1 for maize and 2.12 t ha−1 for soybean, compared to yields of 3.20, 9.30 and 2.45 t ha−1 respectively for wheat, maize and soybean if the crop nutrient demands were met. At the potential yield level, the N, P and
K removal by wheat are 79 kg N ha−1, 15 kg P ha−1, and 53 kg K ha−1, by maize are 207 kg N ha−1, 47 kg P ha−1, and 180 kg K ha−1, by soybean are 174 kg N ha−1, 18 kg P ha−1, and 55 kg K ha−1. Crop yield, change in soil organic carbon (SOC), and the total and available nutrient status were used to evaluate the fertility
of this soil over different time periods. This study showed that a fertiliser strategy that was able to maintain yields in
the short term (19 years) would not maintain the long term fertility of these soils. Although organic carbon levels did not
rise to the level of virgin soil in any treatment, a combination of N, P and K fertiliser that approximated crop export was
required to stabilise SOC and prevent a decline in the total store of soil nutrients. 相似文献