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31.
K. Aihou N. Sanginga B. Vanlauwe O. Lyasse J. Diels R. Merckx 《Agroforestry Systems》1998,42(3):213-227
The potential of alley cropping systems supplied with a limited amount of fertilizer to restore crop productivity on a degraded
site and to maintain crop productivity on a recently cleared, non-degraded site on ‘terre de barre‘ soils in Southern Bénin
was investigated from 1994 to 1996. Leucaena leucocephala, Senna siamea and Gliricidia sepium were used as hedgerow species.
Maize yields of the no-tree control plots dropped from the initial (1990) 401 kg ha−1 and 2181 kg ha−1 on the degraded and
non-degraded sites, respectively, to 109 kg ha−1 and 1346 kg ha−1 in 1996, even with application of a minimal amount of mineral
fertilizer. The alley cropping systems produced on average (mean of three treatments and three years) 107% more grain than
the initial 1990 values on the degraded site and 11% less grain than the initial 1990 values on the non-degraded site. Especially
the Senna and to a lesser degree the Leucaena treatment yielded consistently more grain than the control. The Senna trees
contained a larger amount of N and produced more wood during the first pruning on the degraded site (155 kg N ha−1 and 14.0
ton fresh wood ha−1) than on the non-degraded site (49 kg N ha−1 and 6.6 ton fresh wood ha−1) most likely because of differences
in subsoil fertility, as indicated by the higher clay, exchangeable bases, and N content between 60 and 125 cm cm. N accumulation
and wood production by the Leucaena and Gliricidia trees was similar in both sites (82 and 36 kg N ha−1 and 4.6 and 9.3 ton
fresh wood ha−1, respectively). When a limited amount of fertilizer is available, Senna appears to be the best choice as hedgerow
species on sites with a relatively fertile subsoil. For other soils, a N2-fixing species may be a better choice.
This revised version was published online in June 2006 with corrections to the Cover Date.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
32.
Populations of plant parasitic nematodes and their effects on symbiotic nitrogen (N) fixation in herbaceous legumes and on
some selected characteristics of other plant species associated with such cover crops were studied. Two legume species [mucuna,
Mucuna pruriens (L) DC. var. utilis (Wright) Bruck and lablab, Lablab purpureus L. Sweet], one grass/weed species [imperata, Imperata cylindrica (L.) Rauschel] and a cereal (maize, Zea mays L.) were used. There were three soil treatments (fumigation, fumigation plus inoculation with Meloidogyne species, and an untreated control). Plant parasitic nematode populations in soil, roots and nodules were determined at 4,
8 and 12 weeks after planting. The response of the phytoparasitic nematodes to soil treatments varied according to the plant
species present. The predominant nematodes in soils, roots and nodules of legumes were of the genus Meloidogyne, whereas other genera of parasitic nematodes dominated the fauna in soils and roots of maize and imperata. Biomass yield
of mucuna was not significantly affected by either Meloidogyne spp. or the other genera of phytoparasitic nematodes. In contrast, the dry matter yield of lablab measured at 12 weeks was
reduced by 16% in inoculated compared with fumigated soils. Similarly, the biomass yields of maize and imperata were reduced
by 10% and 29%, respectively, in unfumigated rather than fumigated soils. The amounts of N accumulated in mucuna, maize and
imperata were not significantly affected by the two groups of plant parasitic nematodes. However, at 12 weeks, lablab grown
on inoculated soils accumulated only 69% of the N found in plants grown on fumigated soils. Inoculation of soil with Meloidogyne spp. significantly increased the number of nodules on lablab roots compared with the non-inoculated treatments, whereas nodulation
in mucuna was not affected by soil treatment. After 12 weeks, the quantity of N2 derived from symbiotic fixation in mucuna was not significantly affected by soil treatments whereas the amount of fixed N
in lablab was 32% lower in inoculated than in fumigated soils. Possible mechanisms for the non-suppressive effect of plant
parasitic nematodes on mucuna are discussed.
Received: 12 March 1999 相似文献
33.
Transformations and recovery of residue and fertilizer nitrogen-15 in a sandy Lixisol of West Africa
The fate of 15N-labeled plant residues from different cover-cropping systems and labeled inorganic N fertilizer in the organic, soil mineral,
microbial biomass and soil organic matter (SOM) particle-size fractions was investigated in a sandy Lixisol. Plant residues
were from mucuna (legume), lablab (legume), imperata (grass), maize (cereal) and mixtures of mucuna or lablab with imperata
or maize, applied as a surface mulch. Inorganic N fertilizer was applied as 15N-(NH4)2SO4 at two rates (21 and 42 mg N kg–1 soil). Total N release from mucuna or lablab residues was 2–3 times higher than from the other residues, whereas imperata
immobilized N throughout the study period. In contrast, 15N was mineralized from all the plant residues irrespective of the mineralization–immobilization pattern observed for total
N. After 168 days, 69% of soil mineral N in mucuna- or lablab-mulched soils was derived from the added residues, representing
4–8% of residue N, whereas 9–30% of inorganic N was derived from imperata, maize and the mixed residues. At the end of the
study, 4–19% of microbial biomass N was derived from the added residue/fertilizer-N, accounting for 1–3% of added residue-N.
Averaged across treatments, particulate SOM fractions accounted for less than 1% of the total soil by weight but contained
20% of total soil C and 8% of soil N. Soils amended with mucuna or lablab incorporated more N in the 250–2000 μm SOM pool,
whereas soil amended with imperata or the mixed residues incorporated similar proportions of labeled N in the 250–2000 μm
and 53–250 μm fractions. In contrast, in soils receiving the maize or inorganic fertilizer-N treatments, higher proportions
of labeled N were incorporated into the 53–250 μm than the 250–2000 μm fractions. The relationship between these differences
in residue/fertilizer-N partitioning into different SOM particle-size fractions and soil productivity is discussed.
Received: 12 March 1999 相似文献
34.
B. Vanlauwe K. Aihou S. Aman B. K. Tossah J. Diels O. Lyasse S. Hauser N. Sanginga R. Merckx 《Biology and Fertility of Soils》2000,30(5-6):440-449
The impact of land use (unfertilized continuous maize cropping, unfertilized and fertilized alley cropping with maize, Gliricidia sepium tree fallow, natural fallow) on the soil organic matter (SOM) status and general soil fertility characteristics were investigated
for a series of soils representative for the West African moist savanna zone. Three soils from the humid forest zone were
also included. In an associated pot experiment, relationships between maize N and P uptake and SOM and general soil characteristics
were developed. Soils under natural fallow contained the highest amount of organic C (1.72%), total N (0.158%), and had the
highest effective cation exchange capacity (ECEC) [8.9 mEq 100 g–1 dry soil], while the Olsen P content was highest in the fertilized alley cropping plots (13.7 mg kg–1) and lowest under natural fallow (6.3 mg kg–1). The N concentration of the particulate organic matter (POM) was highest in the unfertilized alley cropping plots (2.4%),
while the total POM N content was highest under natural fallow (370 mg N kg–1) and lowest in continuously cropped plots (107 mg N kg–1). After addition of all nutrients except N, a highly significant linear relationship (R
2=0.91) was observed between the total N uptake in the shoots and roots of 7-week-old maize and the POM N content for the savanna
soils. POM in the humid forest soils was presumably protected from decomposition due to its higher silt and clay content.
After addition of all nutrients except P, the total maize P uptake was linearly related to the Olsen P content. R
2 increased from 0.56 to 0.67 in a multiple linear regression analysis including the Olsen P content and clay content (which
explained 11% of the variation in P uptake). Both the SOM status and N availability were shown to be improved in land-use
systems with organic matter additions, while only the addition of P fertilizer could improve P availability.
Received: 9 April 1999 相似文献
35.
There is increasing interest in farmers’ organizations as an effective approach to farmer participatory research (FPR). Using data from an empirical study of farmers’ research groups (FRGs) in Uganda, this paper examines the patterns of participation in groups and answers questions such as: Who participates? What types of participation? How does participation occur? What are the factors determining participation? Results show that there is no single type of participation, but rather that FPR is a dynamic process with types of participation varying at different stages of the process. Farmers’ participation does not follow the normal adoption curve. Rather, it is characterized by high participation at the initial stages, followed by dramatic decrease and dropping-out, and slow increases toward the end. There is usually significantly higher participation among male farmers at the beginning of the process. However, as FRGs evolve, the proportion of men decreases sharply while the relative proportion of women continues to increase until it dominates the group. The findings do not support the common assumption that groups usually exclude women and the poor. On the contrary, we argue that FRGs are an effective mechanism to provide women and the poor with opportunities to participate in research. However, to be effective, this requires moving beyond head counting to promote more proactive gender and equity perspectives for amplifying the benefits of agricultural research to those who tend to be marginalized or excluded by mainstream development initiatives. This will be critical for making agricultural research more client-oriented and demand-driven. 相似文献