摘要:

Conservation tillage covers a wide spectrum of production systems, ranging from zero-tillage systems to reduced tillage systems, using various forms of traction; manual, animal or tractor. Each conservation tillage system forms part of, and interacts with, the prevailing farming system (e.g., mulch-fodder conflicts), which in turn will affect physical and socio-economic parameters on a watershed scale (e.g., upstream/downstream water availability and labour allocation). In this paper results are presented from on-farm conservation tillage experiments in Tanzania. The focus is not only on yield data from different tillage systems but also on the participatory research method used in carrying out the trials. The results indicate a large potential of achieving substantial increases in staple food crop yields and reduced traction needs, by adopting conservation tillage systems designed to fit in prevailing socio-economic and agro-ecological environments.

ISSN:0012-8325    

DOI:10.4314/eaafj.v65i1.1762

出版商:Taylor & Francis    

年代:1999

数据来源: Taylor

摘要:

Deterioration in soil hydraulic properties due to deforestation adversely affects the hydrology of catchments, especially those on mountain slopes. The effects of clearing natural forest (NF) for potato cultivation (PC) and livestock grazing (GL) on the hydraulic properties of an andosol (after 5 to 8 years) were investigated in the northern slopes of Mount Kenya. The two farming activities have resulted in deleterious changes in soil water flow and storage. Results obtained showed that steady infiltration rates were 65.7 in NF, 9.7 in PC and 13.4 cm h−1in GL. Sorptivity decreased by 15% in PC and 22% in GL, while topsoil-saturated hydraulic conductivity decreased by 62% in PC and 76% in GL compared to NF. Both PC and GL topsoil had higher volumetric water content at soil matric potentials (<—25 cm) than NF. Cultivation and grazing in the area have led to compacted topsoil with lower (11%) total porosity and decreased plant available water holding capacity by 16 for PC and 19% for GL.

ISSN:0012-8325    

DOI:10.4314/eaafj.v65i1.1763

出版商:Taylor & Francis    

年代:1999

数据来源: Taylor

摘要:

Field studies were initiated in 1990 to determine the sustainability of traditional and improved management practices. The management practices investigated were cropping density, surface cover (mulch and canopy) and two tillage options involving a conventional, (CT) and a minimum (MT) system. Daily rainfall, runoff, soil loss weekly soil water, mulch cover and seasonal crop yields were measured. Analysis of results of 19 cropping seasons showed that both runoff and soil loss decreased as cover increased. Mulch cover was more effective than the growing crops canopy. Average seasonal runoff declined from 74.4 mm (21.9% of rainfall) in the traditional maize system to 22.3 mm (6.5% of rainfall) in the mulched plots. The effect of low mulch rate was more dramatic in soil loss reduction than in runoff reduction. Crop yield increased with cover, from an average of 1 t ha−1in the traditional maize system to 2.75 t ha−1in the mulched plots. However, this increase was only realised with additional nutrients. CT was superior to MT in terms of runoff and soil erosion reduction. Mean seasonal loss for CT and MT were 30.7 mm and 77.1 mm, respectively, for runoff, and 1.84 t ha−1and 7.78 t ha−1, respectively, for soil erosion. The most sustainable management system consisted of a conventional tillage system, double the traditional farmer maize crop density, retention of approximately 3 t ha−1of maize stubble as mulch and addition of 70 kg ha−1of nitrogen.

ISSN:0012-8325    

DOI:10.4314/eaafj.v65i1.1764

出版商:Taylor & Francis    

年代:1999

数据来源: Taylor

摘要:

The Agricultural Production Systems Simulator (APSIM) model was used to investigate the effects of 40 years of four land management practices. It was calibrated for local conditions using field measurements from 12 runoff plots at Katumani. The model was then validated using the data obtained from treatments conducted over nineteen cropping seasons. The model was initialised using the soil parameters obtained from virgin land, of similar soil type, adjacent to a newly opened farm at the Kathekakai Settlement Scheme.

ISSN:0012-8325    

DOI:10.4314/eaafj.v65i1.1765

出版商:Taylor & Francis    

年代:1999

数据来源: Taylor

摘要:

Landsat Thematic Mapper (TM) and aerial photos were used to assess soil erosion on the western slopes of the Uluguru Mountains in Tanzania. Aerial photos were interpreted using mirror stereoscopes for the classification and production of a land cover map of the sample area. Several attributes were used to categorise the extent of erosion in different land cover classes. These included area under cultivation, slope gradient and presence of erosion features like bare soil, exposed roots of trees and grass tuffs.

ISSN:0012-8325    

DOI:10.4314/eaafj.v65i1.1766

出版商:Taylor & Francis    

年代:1999

数据来源: Taylor

摘要:

Land scarcity is progressively limiting the expansion of agricultural activities in Kenya due to increasing human population. This requires intensification of agricultural production to meet the increasing demand for cash and food (maize). Livestock is an important economic activity for smallholder farmers who produce 80% of marketed milk. However, potential milk production has not been achieved due to continuous feed unavailability both in quantity and quality. Acreage under forages has progressively reduced in preference for food and cash crops. A variety of forages have been developed for smallholder farmers but with limited adoption. The adoption of these forages are influenced by social and economic factors. The objective of this study was to analyse these factors under farmer conditions. The data was collected from on-farm trials carried out in Moiben and Nyatieko. Cost-Benefit analysis using discounted techniques was used to find the profitability of the technologies. The results show benefits accruing from Napier grass and grass leys as viable options. The Net Present Values per hectare at 15% discount rate for Rhodes grass under hay making followed by grazingin situscenario KSh 1,653, Rhodes grass hay making scenario KSh 44,863, Coloured guinea under hay making followed by direct grazing KSh 2,069, Coloured guinea hay making scenario KSh 54,697, Napier grass with 60 kg P2O5ha + 60 kg N ha KSh 37,361, Napier grass 10 t ha−1farm yard manure (FYM) KSh 44 185 and half the rates of inorganic and FYM on Napier grass gave KSh 40,794. These figures show that forage crops economically compete for farm resources when compared to maize crop with an average annual flow of KSh 10,000 giving Net Present Value of KSh 24,360 (for three years) and 31,993 (for five years). Farmer evaluations based on forage persistence and yields rated Rhodes grass and Napier grass as good forages at smallholder level.

ISSN:0012-8325    

DOI:10.4314/eaafj.v65i1.1767

出版商:Taylor & Francis    

年代:1999

数据来源: Taylor

ISSN:0012-8325    

DOI:10.4314/eaafj.v65i1.1751

出版商:Taylor & Francis    

年代:1999

数据来源: Taylor