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1.
This study examined the hypothesis that incorporation of Gliricidia sepium (Jacq.) Walp.) (gliricidia), a fast-growing, nitrogen-fixing tree, into agroforestry systems in southern Malawi may be used
to increase the input of organic fertilizer and reduce the need for expensive inorganic fertilizers. The productivity of maize
(Zea mays L.), pigeonpea (Cajanus cajan L.) and gliricidia grown as sole stands or in mixed cropping systems was examined at Makoka Research Station (latitude 15°
30′ S, longitude 35° 15′ E) and a nearby farm site at Nazombe between 1996 and 2000. Treatments included gliricidia intercropped
with maize, with or without pigeonpea, and sole stands of gliricidia, maize and pigeonpea. Trees in the agroforestry systems
were pruned before and during the cropping season to provide green leaf manure. Maize yields and biomass production by each
component were determined and fractional light interception was measured during the reproductive stage of maize. Substantial
quantities of green leaf manure (2.4 to 9.0 Mg ha−1 year−1) were produced from the second or third year after tree establishment. Green leaf manure and fuelwood production were greatest
when gliricidia was grown as unpruned sole woodlots (c. 8.0 and 22 Mg ha−1 year−1 respectively). Improvements in maize yield in the tree-based systems also became significant in the third year, when c. 3.0 Mg ha−1 of grain was obtained. Tree-based cropping systems were most productive and exhibited greater fractional light interception
(c. 0.6 to 0.7) than cropping systems without trees (0.1 to 0.4). No beneficial influence of pigeonpea on maize performance
was apparent either in the presence or absence of gliricidia at either site in most seasons. However, as unpruned gliricidia
provided the greatest interception of incident solar radiation (>0.9), coppicing may be required to reduce shading when gliricidia
is grown together with maize. As pigeonpea production was unaffected by the presence of gliricidia, agroforestry systems containing
gliricidia might be used to replace traditional maize + pigeonpea systems in southern Malawi.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
Nitrogen deficiency is widespread in southern Africa, but inorganic fertilizers are often unaffordable for smallholder farmers. Short-duration leguminous fallows are one possible means of soil fertility restoration. We monitored preseason topsoil (0 to 20 cm) ammonium and nitrate, fallow biomass production and grain yields for three years in a relay cropping trial with sesbania [Sesbania sesban (L.) Merr.] and maize (Zea mays L.). Sesbania seedlings were interplanted with maize during maize sowing at 0, 7400 or 14,800 trees ha–1, in factorial combination with inorganic N fertilizer at 0 or 48 kg N ha–1 (half the recommended rate). After maize harvest, fallows were allowed to grow during the seven-month dry season, and were cleared before sowing the next maize crop. Both sesbania fallows and inorganic N fertilizer resulted in significantly greater (P < 0.01 to 0.05) preseason topsoil nitrate-N than following unfertilized sole maize. In plots receiving no fertilizer N, preseason topsoil inorganic N correlated with maize yield over all three seasons (r
2 = 0.62, P < 0.001). Sesbania fallows gave significantly higher maize yields than unfertilized sole maize in two of three years (P < 0.01 to 0.05). Sesbania biomass yields were extremely variable, were not significantly related to sesbania planting density, and were inconsistently related to soil N fractions and maize yields. Short-duration fallows may offer modest yield increases under conditions where longer duration fallows are not possible. This gain must be considered against the loss of pigeonpea (Cajanus cajan L. Millsp) harvest in the similarly structured maize-pigeonpea intercrop common in the region.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
3.
The study investigated diversity and frequency of occurrence of glomale (Arbuscular- or Vesicular Arbuscular-) mycorrhizal
fungi on three farming systems in a drought prone and nitrogen deficiency site in southern Malawi. The farming systems comprised
of two agroforestry systems of Sesbania sesban (L) Merr intercropped with maize and Sesbania macrantha E Phillips & Hutch. intercropped with maize and a maize monocrop systems without fertilizer, with nitrogen, phosphorus and
a combination of nitrogen and phosphorus. Species diversity and species frequency of occurrence were examined in soil samples
obtained in the dry and wet seasons. Twelve glomale mycorrhizal species were recorded, four species being in the genus Acaulospora, four in Glomus, two in Gigaspora and two in Scutellospora. Species diversity in the two agroforestry systems were not significantly (p ≤ 0.05) different but had lower species diversity than maize monocrop with only Sesbania macrantha intercropped with maize significantly (p ≤ 0.05) lower. Species diversity was significantly increased by the inorganic nitrogen fertilizer. Inorganic phosphorus fertilizer
had no effect. The study shows that the occurrence and persistence of glomale species are influenced by agroforestry combinations,
and that the spores of most species are tolerant to dry conditions. Only four species responded to fertilizer application
with the occurrence of spores of some species high and some low. Management practices have great implication in the persistence
of spore propagules of glomale species.
The order Glomale was revised in 2001 and upgraded to a phylum Glomeromycota. 相似文献
4.
In order to assess the possibility of root competition in agroforestry, the vertical distribution of fine roots (< 2 mm in
diameter) of five tree species in pure two-year-old stands was compared to that of mature maize.Cassia siamea, Eucalyptus tereticornis, Leucaena leucocephala andProsopis chilensis had a rooting pattern similar to that of maize, i.e. a slow decline in fine root mass from 0–100 cm soil depth.Eucalyptus camaldulensis had its roots evenly distributed down to 100 cm. On an average, the fine root biomass of the tree species was roughly twice
as that of the maize. We conclude that the studied tree species are likely to compete with maize and other crops with a similar
rooting pattern for nutrients and water. 相似文献
5.
The homegardens are characterised by an intensive integration of numerous multipurpose trees and shrubs with food crops and animals, simultaneously on the same unit of land.The Chagga are skilled farmers with an intimate knowledge of the crops and their ecological requirements. They have a good idea of functions/uses of the plant species on their farms. The large species diversity provides both subsistence and cash crops. It enables the farmer to keep his management options open and provides insurance against drought, pest and economic risks. 相似文献
6.
The water dynamics of cropping systems containing mixtures of Gliricidia sepium (Jacq.) Walp trees with maize (Zea mays L.) and/or pigeonpea (Cajanus cajan L.) were examined during three consecutive cropping seasons. The trees were pruned before and during each cropping season, but were left unpruned after harvesting the maize; prunings were returned to the cropping area in all agroforestry systems to provide green leaf manure. The hypothesis was that regular severe pruning of the trees would minimise competition with crops for soil moisture and enhance their growth by providing additional nutrients. Neutron probe measurements were used to determine spatial and temporal changes in soil moisture content during the 1997/98, 1998/99 and 1999/00 cropping seasons for various cropping systems. These included gliricidia intercropped with maize, with and without pigeonpea, a maize + pigeonpea intercrop, sole maize, sole pigeonpea and sole gliricidia. Soil water content was measured to a depth of 150 cm in all treatments at 4–6 week intervals during the main cropping season and less frequently at other times. Competition for water was apparently not a critical factor in determining crop performance as rainfall exceeded potential evaporation during the cropping season in all years. The distribution of water in the soil profile was generally comparable in all cropping systems, implying there was no spatial complementarity in water abstraction by tree and crop roots. However, available soil water content at the beginning of the cropping season was generally lower in the tree-based systems, suggesting that the trees continued to deplete available soil water during the dry season. The results show that, under rainfall conditions typical of southern Malawi, the soil profile contains sufficient stored water during the dry season (ca. 75–125 mm) to support the growth of gliricidia and pigeonpea, and that gliricidia trees pruned before and during the cropping season did not deleteriously compete for water with associated crops. Water use efficiency also appeared to be higher in the tree-based systems than in the sole maize and maize + pigeonpea treatments, subject to the proviso that the calculations were based on changes in soil water content rather than absolute measurements of water uptake by the trees and crops. 相似文献
7.
This study tested the hypothesis that incorporation of green leaf manure (GLM) from leguminous trees into agroforestry systems
may provide a substitute for inorganic N fertilisers to enhance crop growth and yield. Temporal and spatial changes in soil
nitrogen availability and use were monitored for various cropping systems in southern Malawi. These included Gliricidia sepium (Jacq.) Walp. trees intercropped with maize (Zea mays L.), with and without pigeonpea (Cajanus cajan L.), sole maize, sole pigeonpea, sole gliricidia and a maize + pigeonpea intercrop. Soil mineral N was determined before
and during the 1997/1998, 1998/1999 and 1999/2000 cropping seasons. Total soil mineral N content (NO3− + NH4+) was greatest in the agroforestry systems (p<0.01). Pre-season soil mineral N content in the 0–20 cm horizon was greater in treatments containing trees (≤85 kg N ha−1) than in those without (<60 kg ha−1; p<0.01); however, soil mineral N content declined rapidly during the cropping season. Uptake of N was substantially greater
in the agroforestry systems (200–270 kg N ha−1) than in the maize + pigeonpea and sole maize treatments (40–95 kg N ha−1; p<001). Accumulation of N by maize was greater in the agroforestry systems than in sole maize and maize + pigeonpea (p<0.01); grain accounted for 55% of N uptake by maize in the agroforestry systems, compared to 41–47% in sole maize and maize + pigeonpea.
The agroforestry systems enhanced soil fertility because mineralisation of the applied GLM increased pre-season soil mineral
N content. However, this could not be fully utilised as soil N declined rapidly at a time when maize was too small to act
as a major sink for N. Methods for reducing losses of mineral N released from GLM are therefore required to enhance N availability
during the later stages of the season when crop requirements are greatest. Soil mineral N levels and maize yields were similar
in the gliricidia + maize and gliricidia + maize + pigeonpea treatments, implying that addition of pigeonpea to the tree-based
system provided no additional improvement in soil fertility. 相似文献
8.
Domestication and improvement of traditionally used wild indigenous fruit trees hold great promise in agroforestry development. Strychnos cocculoides is a wild indigenous fruit tree that was ranked third by farmers and is one of the priority species chosen for domestication in southern Africa. This study was conducted with the objective of determining the variability in fruit, seed and germination characteristics of four populations of Strychnos cocculoides collected from Zambia. Results showed significant differences (P < 0.05) between and within provenances in fruit, pericarp and pulp weights. Fruits from Kalulushi provenance were heaviest (296 g) whereas the lightest were Petauke provenance fruits (158 g). The pulp content of heavy and light fruits were 52.8% and 47.6% respectively. There was no significant difference (P > 0.05) in the number of seeds per fruit within and between the provenances. In contrast, the seed weight was significantly different (P < 0.05) within and between provenances. The heaviest seeds were found in the heaviest fruits — Kalulushi while the lightest were found in Serenje provenance. Fruit weight was positively correlated with pulp weight (P < 0.001, r = 0.70), pericarp weight (P < 0.001, r = 0.54) and seed weight (P < 0.001, r = 0.76). The provenances differed significantly (P < 0.05) in cumulative germination percentage, ranging from 56 (Kalulushi) to 83 (Kasama).This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
9.
In order to assess the possibility of root competition in agroforestry, the vertical distribution of fine roots (< 2 mm in diameter) of five tree species in pure two-year-old stands was compared to that of mature maize.Cassia siamea, Eucalyptus tereticornis, Leucaena leucocephala andProsopis chilensis had a rooting pattern similar to that of maize, i.e. a slow decline in fine root mass from 0–100 cm soil depth.Eucalyptus camaldulensis had its roots evenly distributed down to 100 cm. On an average, the fine root biomass of the tree species was roughly twice as that of the maize. We conclude that the studied tree species are likely to compete with maize and other crops with a similar rooting pattern for nutrients and water. 相似文献
10.
A. O'kting'ati J. A. Maghembe E. C. M. Fernandes G. H. Weaver 《Agroforestry Systems》1985,2(3):177-186
An inventory of plant species was conducted on farms, farm boundaries and homesteads in the Kilimanjaro agroforestry system. The survey covered 30 farms in 6 villages in Hai District on the slopes of Mount Kilimanjaro, Tanzania. Over 100 plant species spread over 40 families were identified and their uses obtained through interviews with farmers. The species identified include 53 tree species, 29 food crop species, 21 non-woody plants of economic value and 8 weed species. The food crops, trees and other economically useful plants are carefully chosen by the local farmers and intimately intercropped on the same unit of land. In most cases, the plants had two or more uses of which food, fuelwood, medicine, poles, timber and fodder were the most important. 相似文献