Effects of phosphorus on yield of cowpea cultivars intercropped with pearl millet on Psammentic paleustalf in Niger

Phosphorus (P) is the most limiting soil nutrient in the sandy soils of Niger and farmers rarely use chemical fertilizers in producing pearl millet and cowpea. A 3-yr study was conducted in farmer's fields at two locations in South Western Niger to investigate yield response of six cowpea cultivars to applied P-fertilizer (0, 8, 16 kg ha(-1)) when intercropped with millet. Significant yield differences were found between cultivars for their seed and dry fodder yield at all rates of applied P. Cultivars responded differently to the application of P. Millet grain was more than doubled with the addition of 8 to 16 kg P ha(-1). Cowpea cultivars did not have significant differential effect on millet yields. Cowpea cultivars differed significantly in the accumulation of P in fodder with the highest yielding cultivars taking up more P than the low yielding ones. The results have important implications for breeding and selection of cowpea cultivars that are adapted to a range of fertility levels

Integrated Management of Soil Fertility and Land Resources in Sub-Saharan Africa: Involving Local Communities

The soils of sub-Saharan Africa are characterized by their poverty in nutrients along with low clay and organic carbon content and low exchange capacity. There is high pressure on land resources with the quick growth of population and demand for food. Maintaining the fertility of cultivated soils and land resources is a challenge. Since the paradigm of “external input” in the 1960s and 1970s, to the latest concept of integrated soil fertility management, most of the approaches remain crop oriented or livestock oriented with less attention to local communities (LC), which are at the heart of land resource management. This chapter suggests a new integrated and holistic approach involving LC for land resources management, including cultivated soils and rangelands. A global framework is proposed for development of management options of land resources with LC. It is a dynamic process of participative management of lands as providers of services for the entire community

Rotation and nitrogen fertilizer effects on pearl millet, cowpea and groundnut yield and soil chemical properties in a sandy soil in the semi-arid tropics, West Africa

A 5-year study was conducted from 1988 to 1992 at three sites in Niger to determine the effects of crop rotation of a cereal and legumes and nitrogen fertilizer on chemical properties of the soil (0-20 cm) and yield of pearl millet (Pennisetum glaucum), cowpea (Vigna unguiculata), and groundnut (Arachis hypogaea). Four N levels (0-45 kg N/ha) and rotation treatments including continuous fallow were investigated. Soil samples taken from the top 20 cm depth at the end of the experiment from treatments without nitrogen application which included continuous fallow, fallow-millet rotation, groundnut-millet rotation, cowpea-millet rotation, and continuous millet were analysed for soil pH, organic carbon, total nitrogen and exchangeable bases. Fertilizer N significantly increased yield of pearl millet, cowpea and groundnut. Continuous monocropping of pearl millet resulted in lower yields across N levels compared to legume-millet rotations. Legume yields were also consistently lower in monoculture than when rotated with millet. There was a decline in organic matter under continuous millet, cowpea-millet rotation and groundnut-millet rotation. The fallow-millet rotation supplied more mineral N than the legume-millet rotations. Nitrogen availability was greater in cowpea-millet rotation than continuous millet. Crop rotation was more productive than the continuous monoculture but did not differ in maintaining soil organic matter. The legume-millet rotation at 30 kg/ha N appears to be the most viable for millet production. Research should focus on understanding the effect of legume/cereal intercrops and rotations on soil productivity

Performance evaluation of various agroforestry species used in short duration improved fallows to enhance soil fertility and sorghum yields in Mali

The general soil fertility and crop yield decline constraints have guided the Malian agricultural research institute (Institut d’ Economie Rurale, IER), the Sahel Program of the World Agroforestry Centre (ICRAF) and the International Crops Research Institute for the Semi Arid Tropics (ICRISAT) to join efforts and undertake research activities aimed at mitigating the constraints in Mali. Thus, from the year 2000, 14 different trees and shrubs are being tested in improved fallow systems to find which ones perform best to replenish soils and improve crop yields. The results have (i) identified most suited species for 1 or 2 yr improved fallows, (ii) determined their impact on sorghum grain yields and (iii) documented the remnant effects of their impact on soil fertility and crop yields..

The effect of crop residue and fertilizer use on pearl millet yields in Niger

A field study was conducted over a 4-year period in Niger, West Africa, to determine the effects of crop residue (CR), fertilizer, or a combination of crop residue and fertilizer(CRF) on yields of pearl millet(Pennisetum glaucum[L.] R.Br.). Despite a decline in yields of control plots (initial yields were 280kg grain ha-1 declining to 75 kg grain ha - 1 over 4 years), yield of fertilizer plots were maintained at 800-1,000 kg grain ha-1. Continued application of CR slowly augmented yields to levels similar to those of the fertilized plots. The effects of CR and fertilizer were approximately additive in the CRF plots. Addition of CR and fertilizer increased soil water use over the control by 57 mm to 268 mm in an average season and helped trap wind-blown soil. These plots tended to exhibit slightly higer soil pH and lower A1 saturation than did the fertilized treatments. Return of CR to the soil resulted in significantly reduced export of most plant nutrients, especially Ca, Mg, and

Overview of long term experiments in Africa

The prevailing low food production in sub-Saharan Africa is an issue of great concern especially since Africa south of the Sahara is the only remaining region of the world where per capita food production has remained stagnant. This chapter reviews long-term experiments in Africa in the context of shifting paradigms related to tropical soil fertility management from first external input paradigm right through to the current Integrated Soil Fertility Management (ISFM) approach, which is a culmination of the participatory methods developed along the paradigm shift. Long term experiments (LTE) are an important source of evidence for soil fertility decline and provide crucial datasets for the development of sustainable management practices for tropical land-use systems and the amelioration of global climatic and environmental change impacts. A survey was undertaken to identify some ongoing long-term trials distributed across east, south and western Africa and in different agro-ecological zones. A long-term Experiment was defined as that extending over a period of over 5 years and more. Results from these trials are discussed in detail. Inference has been drawn from these findings and includes the following key findings: a) All long term trials showed yield decline, often with a relatively rapid fall to a low level equilibrium; b) At all sites, there were positive yield responses to one or more nutrients added as mineral fertilizers, which were consistent for the duration of the experiments highlighting the effectiveness of mine­ral fertilizers in increasing yield in arable farming systems in Africa; c) Soil organic matter (SOM) also declines significantly when land is cultivated; d) Prolonged treatments using only inputs of organic matter also showed yield declines, although the positive impact were sustained longer than for inorganic fertilizers alone in most cases; e) Rotational treatments, including sequences with legume crops and fallow periods had lower yield declines than monocultures; f) The best results invariably were those treatments that combined inorganic and organic input

Physiological determinants of cowpea seed yield as affected by phosphorus fertilizer and sowing dates in intercrop with millet

The interaction of cowpea (Vigna unguiculata (L.) Walp.) cultivars with management factors and environments was analyzed in terms of parameters of a simple physiological model. In one set of experiments seven cultivars were sown at three rates of phosphorus (P) fertilizer (0, 8 and 16 kg P ha−1). In another set, five cultivars were sown on two dates relative to sowing of millet (Pennisetum glaucum (L.) R.Br.). All experiments involved factorial combinations of management and cultivar treatments, and were conducted in 1988 and 1989 at two sites in western Niger. Seed yield, shoot dry matter, vegetative (Dv) and reproductive (Dr) durations were determined and crop growth rate (C) and partitioning (p) to seed estimated Application of P increased seed yield by increasing C. As sowing was delayed from 1 to 3 weeks after the millet was sown, there was a reduction in seed yield due to decreases in C, Dv and Dr. Variation in cultivar performance across years was mainly a function of C and partitioning. In both experiments the C of the landrace Sadore Local was greater than that of other cultivars, although the partitioning to seed of this cultivar was unstable due to variable control of insect pest damage It is concluded that the primary causes of G × E interactions were differential canopy development and insect damage effects. Therefore in the development of cowpea cultivars for intercropping with millet, emphasis should focus on light capture capabilities. Improved yields would then seem possible with most cultivars, providing insect damage is controlled

Evaluation of application timing in fertilizer micro-dosing technology on millet production in Niger, West Africa

Micro-dosing technology has been developed by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) and its partners to help subsistence farmers in the Sahel improve inorganic fertilizer application. However, the ICRISAT's recommendations regarding fertilizer application through this technology are only applicable at sowing and do not allow any flexibility in terms of labor and/or capital management. In rural areas, fertilizer cannot always be applied at sowing due to financial and labor constraints. The purpose of this study was to evaluate the effect of the timing of fertilizer application on millet production. A 2-year on-station experiment and a 1-year on-farm field experiment were conducted in the western region of Niger, West Africa. Even under the heterogeneous climatic conditions of the region during our experimental period, the results showed that the trend was the same as observed in previous studies: millet production improved through fertilizer application compared to the control (without fertilizer). The harvest index was also higher compared to that of the control. This increased production was consistently the same for all application timings. The marginal value-cost ratio on the investment calculated using a budgeting analysis for the on-farm experiment showed that - regardless of application timing - millet farmers who fertilized their fields with inorganic fertilizer made more profit than those who did not (control). This was also true for farmers who were unable to fertilize at sowing - delayed application was still the more profitable option relative to the no fertilizer control. Our results indicate that small subsistence farmers can be offered more options for inorganic fertilizer application timing using the micro-dosing technology. Delayed inorganic fertilizer application can help small farmers who are often labor constrained at the sowing period improve their yields as well as their economic return