Ckk Gachene

Effects of soil management practices and tillage systems on soil moisture conservation and maize yield on a sandy loam in semiarid Kenya

ABSTRACT Maize is an important crop in the high and medium rainfall areas of Kenya and thus, there is a need for additional information on the effect of tillage and soil management practices on water conservation and yield of maize. The objective of this study was to determine the effects of seven soil management practices: bare with conventional tillage (BC), bare with minimum tillage (BM), incorporated mulch with conventional tillage (IMuC), manure with conventional tillage (MaC), manure with minimum tillage (MaM), surface mulch with conventional tillage (SMuC), and surface mulch with minimum tillage (SMuM) on water conservation and yield of maize. Soil water content was greater in minimum tilled plots than in the conventionally tilled (hand hoeing) plots during the study period. This was demonstrated by the manure with minimum tilled treatment, which had the highest soil moisture (7.6% and 8.3%) both at 0-7 cm and 7-23 cm depth. However, when organic matter additions were analyzed separately, it was observed that manure irrespective of tillage had the highest soil moisture in both depths (7.6% and 8.1%). The differences within the treatments occurred when soil water contents were highest shortly after the rains. When the amount of soil water for each management practice was averaged for all the seasons, a significant difference was found at P = 0.0001. Manure (Ma) and surface mulched (Smu) treatments had significantly higher soil moisture content than the other treatments. The higher moisture content found under these treatments was attributed to higher infiltration rates, better cover that reduced the rainfall kinetic energy, and to better structural stability contributed to by higher organic carbon. Compared with the traditional form of hand hoeing, minimum tillage increased available soil water content drastically and crop performance was improved. Grain yields were greatest in manure and lowest in bare treatments. There were significant differences in grain yield in all treatments.

Assessment of erosion damage in Ndome and Ghazi, Taita Taveta, Kenya: Towards an integrated erosion management approach

Aerial photograph interpretation on erosion trends from 1961 to 1998 showed that by 1998, approximately 17 and 50% of agricultural land in Ndome and Ghazi respectively had been permanently lost due to the combined effect of rill, inter-rill, and gully erosion, and sand deposition. Although abnormally heavy rains received between 1996–98 caused much of the present land damage, the severity of the damage was enhanced by inappropriate and persistent human perturbations in the land-system notably through vegetative degradation and destruction of soil structure through inappropriate tillage practices. With soil organic matter contents of 1.6 and 1.9%, and clay ratios of 10.1 and 10.6 for Ndome and Ghazi, respectively, the areas inherent erodibility was considered as high thus pointing to the need for careful use and management of the soil resource. That farmers appreciated only land quality indicators that were visible to the naked eye and that directly affected their subsistence, revealed a knowledge gap that saw damages from intrinsic processes like rill and inter-rill erosion proceed unnoticed. This paper argues that the spread of erosion damage in rural agro-ecosystems is survival-driven. And as a remedy to this problem, there is need for the diversification of livelihood endeavours to alternative off-farm income sources to reduce pressure on the already fragile land resource. Further, being the ultimate implementers of conservation technologies and by virtue of the multiplicity and inter-relation of rural household needs, adoption of an integrated erosion management approach with food security as paramount presents the most practical entry point for sustainable land management in such rural agro-ecosystems.

Green manure/cover crop technology in eastern and central Uganda: development and dissemination.

In 1992, Ugandan National Agricultural Research Organization along with International Center for Tropical Agriculture researchers from Kawanda Agricultural Research Institute initiated collaborative research with farmers in Uganda. Five villages in the vicinity of the Ikulwe District Farmers Institute in Iganga district of eastern Uganda were included. This area represents the traditional banana (Musa sp. L.)-coffee (Coffea L.)-based systems of the Lake Victoria Crescent agro-ecological zone. It has a mean annual rainfall of 1255 mm in a bimodal distribution and soils that are variable but typically have low total soil N as well as low P availability in Ikulwe. Banana, bean (Phaseolus vulgaris L.), sweet potato (Ipomoea batatas [L.] Lam.), cassava (Manihot esculenta Crantz), groundnuts (Arachis hypogaea L.) and maize (Zea mays L.) are important food crops. The approach was participatory, systems oriented and interdisciplinary. Research activities on green manure/cover crops (GMCCs) consisted of some designed by farmers and researchers, and some farmers’ own experimentation. Farmer-researcher trials indicated that yields of the GMCC species were reduced 40–70% when intercropped with a food crop as compared to sole crop production and that yields of food crops were reduced 61–87% when intercropped with Crotalaria ochroleuca G. Don. In contrast, maize grain yield response in the first season following sole-crop GMCC production ranged from 0 to 240%. These trials also indicated that Mucuna pruriens (L.) DC. and Lablab purpureus (L) Sweet were best for weed suppression and for control of soil erosion, that tillage and weeding requirements can be much less following GMCCs and that maize can often be planted directly in the holes left from uprooting Mucuna and Lablab, reducing labour requirements the following season. Land productivity was not improved with alley cropping. Farmers initiated trials on their own, such as on Tephrosia vogelii Hook. f. to control mole rats, which indicated effective control and resulted in significant adoption by neighbouring farmers. Other farmer experimentation focused on intercropping GMCCs with coffee, banana with Canavalia ensiformis (L.) DC., cassava and sweet potato, and Mucuna with maize.

Soil chemical properties, sunflower growth and yields as affected by double digging, mulch and compost in central Kenya

Double digging as a form of deep tillage and the between late October and late December. The utilisation of compost and mulch for improved crop experiments were conducted on a humic Nitisol production in the densely populated areas of Kenya (FAO-UNESCO, 1988) whose characteristics are is rapidly gaining attention the Kenya Institute of presented in Table I. Organic Farming (KIOF, 1994). The aim of double digging is to loosen the deep soil layers for intensive crop production. Compost is aimed at supplying essential plant nutrients and enhancing soil physical properties through addition of organic matter (FAO, 1977; Pfirter et al., 1981). Organic matter has beneficial effects on soil fertility because it increases nutrient storage capacities (Tisdale et al., 1985; Woomer et al., 1995). Mulch modulates soil diurnal temperature, reduces evaporative soil water loss and improves infiltration (Russell, 1988). All these have positive influences on crop growth.

Using Forage Legumes to Improve Soil Fertility for Enhanced Grassland Productivity of Semi-arid Rangelands of Kajiado District, Kenya

A two-phase study was conducted in the semi-arid rangelands of Kajiado District, Kenya, to determine the effect of forage legumes on soil fertility improvement and grassland productivity of natural pastures. During legume evaluation phase, Neonotonia wightii (Glycine), Macroptilium atropurpureum (Siratro), Lablab purpureus cv. Rongai (Dolichos), Mucuna pruriens (Velvet bean) and Stylosanthes scabra var. seca (Stylo) were screened for adaptability and growth performance. Results of soil analysis showed that soil pH, organic carbon, nitrogen and potassium significantly increased after 2 years of study due to the large amounts of organic residues produced by the legumes (particularly the perennials). The calcium content decreased significantly (which was attributed to plant uptake) while the decrease of phosphorus was not significant. After integration of Glycine, Siratro and Stylo into natural pastures during the second phase of the study, the crude protein content of grasses intercropped with legumes increased from 7.1 to 14.3, 11.9 and 10.2%, respectively. Grasses intercropped with legumes also had higher digestibility contents than grasses in monoculture stands. The study concluded that addition of organic residues by the introduced forage legumes improved the soil fertility status and hence the crude protein and digestibility of grasses.

Promotion of Marejea Cultivation in the Ruvuma Region of Tanzania: Experiences of the Catholic Missionaries at Peramiho Mission Centre

The existing information on marejea (Crotalaria ochroleuca G. Don) work in the Ruvuma region of Tanzania indicates that the crop has the potential to improve soil fertility and control weeds. It can also be used for feeding animals. Although the main purpose of promoting marejea in the region was for improving soil fertility, because of the incentives offered, it rather became an exercise of seed bulking. Farmers were enthusiastic to cultivate marejea as long as incentives were provided. Once they were withdrawn, interest waned. Two workshops, held in 1986 and 1987, were important in creating a forum to discuss a number of issues related to the use and adoption of marejea in the region. However, there was no follow-up after the workshops. The number of farmers currently growing marejea and their reasons for continuing the practice are not known. A study documenting this could be a starting point for efforts to reintroduce the crop in the region.

Field Assessment of the Effect of Cumulative Soil Loss on Soil Productivity

Soil erosion affects physical and chemical soil properties by reducing water infiltration rates, soil water holding capacity, soil fertility and leading to deterioration of soil structure. Research on the relationship between erosion and soil physical and chemical properties has been conducted (Battison et al., 1987; Becher et al., 1985; Frye et al., 1982) but few such studies have been carried out in the tropics (Mbagwu et al., 1984; Yost et al., 1985; Lal, 1985; Belay, 1992; Casanova et al., 1987; Merete, 1992). Results mostly indicate that erosion causes considerable deterioration of soil fertility and reduces rooting depth, causes soil crusting, compaction, loss of soil water storage capacity, diminishes workability and decreases infiltration rates. Crosson, (1985) argued that consequences of eroded soil carried off the farm are not always negative. Some eroded fertile soil may be deposited on less fertile soil, thus enhancing the productivity of the latter. However, the general consensus is that the effect of deposited soil is negative in Kenya (Otieno, 1993; Schneider, 1993).