摘要:

The need to increase crop production on sustainable basis is crucial in the tropics because of poor soil fertility as characterised by low nitrogen and phosphorus status. Agroforestry entails inclusion of woody perennials (trees and shrubs) in a diversified and sustainable land-use system. Use of nitrogen-fixing trees and shrubs (NFTs) in agroforestry systems is specifically to conserve the production potential of such systems due to the inherent ability of NFTs to improve the nutrient status of the soil. Appropriate manipulation and management of the micro-symbiont and macro-symbiont enhances biological nitrogen fixation (BNF) in an agroforestry system that incorporates NFTs as tree/shrub components. This paper highlights the technologies available for ensuring optimal exploitation of BNF in the agroforestry context and also points out some of the misconstructions about nitrogen-fixing symbioses.

ISSN:0012-8325    

DOI:10.1080/00128325.1996.11663298

出版商:Taylor & Francis    

年代:1996

数据来源: Taylor

摘要:

The performance of contour hedgerows for soil and water conservation in the drylands was examined in terms of the ‘water cost’ as transpired by the trees and the ‘amount saved’ as reduction in runoff. Analysis of long-term data obtained from Machakos District, Kenya, showed that the water cost of 4-m contour hedgerows exceeded the amount saved by 3–4 times, indicating that research should focus on wider spaced (12–14-m) hedgerows even though narrow hedgerows are more efficient than grass strips in both soil conservation and overall water utilisation. Future research should also include trees which can enhance soil fertility as well as soil conservation, use economically useful tree species, and examine the constraints to farmers' adoption of such technologies.

ISSN:0012-8325    

DOI:10.1080/00128325.1996.11663299

出版商:Taylor & Francis    

年代:1996

数据来源: Taylor

摘要:

This paper suggests that the use of fodder multi-purpose tree (MPT) species is a viable option for protein and mineral supplementation for the small-holder dairy farms. The paper reviews some past and current research on fodder MPTs in Kenya with regard to choice of species, establishment and management and highlights the challenges ahead. Nutrition is the most limiting factor to small-holder dairy production. Napier grass (Pennisetum purpureum), with limited amounts of crop stover and other on-farm roughages, form the basic diet. The quantity, nutritive quality and seasonal distribution, however, do not satisfy the animal requirements, thus necessitating supplementation. Use of commercial supplements and inclusion of herbaceous legumes in Napier grass are possible supplemental options but for a variety of reasons, levels of commercial supplement feeding and the adoption of herbaceous legumes by the small-holder farmers are very low.

ISSN:0012-8325    

DOI:10.1080/00128325.1996.11663300

出版商:Taylor & Francis    

年代:1996

数据来源: Taylor

摘要:

Although the technical advantages in terms of animal production and improved soil fertility of the use of herbaceous legumes have been well demonstrated in Kenya and elsewhere, adoption by small-scale farmers has been disappointing. This has led to increased research into the use of both indigenous and exotic fodder trees. In common with conventional pasture legumes, tree fodders contam high levels of crude protein and minerals and many show high levels of digestibility. They are readily accepted by livestock and because of their deep-root systems, they continue to produce well into the dry season. Anti-nutritive factors can be a problem however, and polyphenolics, toxic amino acids, cyanogenic glycosides and alkaloids are found in many tree species. There are abundant niches on small farms where fodder trees can be grown without affecting crop production. In the Embu region, it has been estimated that 3 kg of fresh fodder ofCalliandra calothyrsushas the same effect on milk production as 1 kg of commercial dairy meal. Up to about 500 trees (250 m of hedgerow) will produce enough fodder to supplement one dairy cow for a complete lactation. The tree fodder can either replace the concentrate without loss of yield, or it can complement it to produce more milk. Calliandra is being enthusiastically adopted by small-scale farmers, many of whom are starting to produce their own seed. Other tree species are now being studied to avoid over-reliance on a single fodder species.

ISSN:0012-8325    

DOI:10.1080/00128325.1996.11663301

出版商:Taylor & Francis    

年代:1996

数据来源: Taylor

摘要:

Three field experiments were carried out to test the response of maize grain yield to the application of green manure from five species of shrubs and one tree species in four sites in Western Kenya. The species tested wereSenna (=Cassia) spectabilis, Lantana camara, Tithonia diversifolia, Calliandra calothrysus, Psidium guajava(guava) andGrevillea robusta.At two of the experimental sites, groups of farmers tested the response of maize to the application of green manure from tithonia and lantana under their own field conditions and management. The rate of green manure application ranged from 5 to 20 t/ha on dry matter basis. The control plot that was adopted in this experiment was a continously cropped plot which did not receive green manure. Tithonia and lantana green manure gave the highest maize grain yields (4–5 t/ha) when applied at the rate of 5 t/ha but there were no yield differences between treatments with the two species when the rate of application of green manure was increased to 10 and 20 t/ha. The residual effect from tithonia and lantana green manure was more pronounced than from treatments with phosphoric fertilisers. Farmers realised comparatively higher maize grain yields from the application of tithonia green manure than from lantana although most them did not apply the prescribed quantitites of the green manure. Tithonia was the more preferred manure spices by farmers.

ISSN:0012-8325    

DOI:10.1080/00128325.1996.11663302

出版商:Taylor & Francis    

年代:1996

数据来源: Taylor

摘要:

This experiment assessed the feasibility of using leaf prunings ofCalliandra calothyrsusandLeucaena leucocephalafor soil fertility improvement in alley cropping and sole cropping systems. The experiment, conducted at the National Agroforestry Research site at the Kenya Agricultural Research Institutes's (KARI's) Regional Research Centre, Embu, was a randomised block design with four alley cropping treatments namely: (1)C. calothyrsuswith primings incorporated; (2)L. leucocephalawith prunings incorporated; (3)C. calothyrsuswith prunings removed to (5); (4)L. leucocephalawith prunings removed to (6); and six sole cropped treatments namely (5)C. calothyrsusprunings imported from (3); (6)L. leucocephalaprunings imported from (4); (7)C. calothyrsusprunings plus fertilizer 25 kg N and P/ha; (8)L. leucocephalaprunings plus fertilizer at 25 kg N and P/ha; (9) Fertilizer at 50 kg N and P/ha, and (10) Control-no fertilizer and no prunings. Biomass production decreased from an average of 6.5 t/ha during the 1993 Long Rainy season (first cutting) to an average of 1.7 t/ha during the 1994 Long Rainy season. This resulted to small amounts of nutrients supplied to the soil by incorporated leaf prunings and could have limited crop growth thus giving low crop yields during 1994 LR. Alley cropped treatments yielded less maize and bean grain than sole cropped treatments during the 1993/94 Short Rainy season; thus was attributed to competition for growth resources. Improvement of crop yields in alley cropping systems through green manuring may be limited by low biomass production and competition. In a sole cropping system, use of green manure to boost crop yields seems feasible with high biomass applications or fertiliser supplementation.

ISSN:0012-8325    

DOI:10.1080/00128325.1996.11663303

出版商:Taylor & Francis    

年代:1996

数据来源: Taylor

摘要:

Monitoring of an existing leucaena crop for the arrival of the psyllid began at Muguga in Kiambu District, Central Province of Kenya late in 1992. An infestation was noted by December the same year and a psyllid population monitoring programme began. This paper presents the findings of a 3-year study of the psyllid population monitored weekly throughout this period. The population was observed to build up gradually over the normal period of growth of leucaena foliage but then collapsed during the hot dry weather (February). This pattern of infestation has been repeated over the years but has been gradually shifting towards

ISSN:0012-8325    

DOI:10.1080/00128325.1996.11663304

出版商:Taylor & Francis    

年代:1996

数据来源: Taylor

摘要:

A field experiment was established to study the effect of cutting management on the fodder yields of a mixed crop of calliandra (Calliandra calothyrsus) and Napier grass (Pennisetum purpureum). Seven treatments were laid out as hedgerows in a randomized complete block design with four replications. Dry matter (DM) yields of calliandra increased significantly (P≤0.05) with cutting height. Most nutrients were not affected by this management except calcium and magnesium which declined. Dry matter yields of Napier grass declined with increasing cutting height of calliandra in the mixture. No significant differences in nutrient content were observed.

ISSN:0012-8325    

DOI:10.1080/00128325.1996.11663305

出版商:Taylor & Francis    

年代:1996

数据来源: Taylor

摘要:

The paper highlights the importance of accounting for socio-economic issues in agroforestry extension. It raises questions about how socio-economic issues can be institutionalised into forestry extension approaches. Forestry extension aims to assist people to improve their socio-economic livelihoods and welfare, and forestry opportunities and needs are determined by their socio-economic situations. A socio-economic approach forms the basis of successful forestry extension. Socio-economic issues also concern the environment within which people live and act. People's socio-economic situations depend on such variables as wealth, income, food security, demography, employment, labour, cultural norms and land tenure. Different groups and individuals have different socio-economic attributes and varying needs for forestry. They also have varying abilities to practise it on their, farms. Thus, agroforestry extension must be targeted to its clients' different socio-economic situations and their accompanying needs, problems and opportunities. Clients' participation in the whole forestry process forms a crucial part of this perspective.

ISSN:0012-8325    

DOI:10.1080/00128325.1996.11663306

出版商:Taylor & Francis    

年代:1996

数据来源: Taylor

摘要:

Acacia tortilis, Prosopis julifloraandCasuarina equisetifoliaprovenances were screened to determine their potential for adaptability under P limiting conditions as a strategy to exploit genotypic differences in terms of utilization and uptake efficiencies. The experiment was conducted in the greenhouse at the Kenya Forestry Research Institute using soils taken from the field which are critically low in available phosphorus (P). The experimental treatments comprised of P application at 0 and 60 Kg P205/ha for 11 provenances ofAcacia, 6 Prosopisand 4Casuarinaspp. Trait for adaptability to P deficiency was determined by measuring the growth performance, P uptake and utilization efficiencies at zero and moderate application of P. The results indicated considerable differences in the growth performance and Phosphorus use efficiency (PUE).Acaciaprovenances showed the highest PUE compared withProsopisandCasuarinaspp although “this was not reflected in the total dry matter yield. However, it was observed that P application resulted in an increase in shoot dry matter, height, root collar diameter and root dry matter in case ofCasuarina.Similarly, the highest total P uptake was obtained inCasuarinaandProsopisspp. The results further indicated that P application probably contributed to the reduction in root, dry matter and root:shoot ratios ofAcaciaandProsopisbut not Casuarina spp.

ISSN:0012-8325    

DOI:10.1080/00128325.1996.11663307

出版商:Taylor & Francis    

年代:1996

数据来源: Taylor