Spatial variability and farmer resource allocation in millet production in Niger

The Sahel of West Africa is the agro-ecological zone located between 12 oand 16 oN, with an annual rainfall of between 300 and 1000 mm. Crops are grown in a subsistence type of agriculture during the 75 to 125 days growing period between May and September. Major crops are millet, sorghum, cowpea, and groundnut, sown usually in mixed-cropping. Crop production suffers from frequent droughts and poor soil fertility, which cause low yields and repeated food shortages. Traditional farming, in the western part of Niger, relies on the use of livestock to combat soil nutrient deficiencies, and other risk minimizing strategies, to produce an average 350 kg ha -1year -1of millet grain. This is the context within which this research was conducted in four localities in western Niger in 1995, 1996, and 1997.The overall aim was to investigate soil and crop variability at various scales and the rightness of traditional land management in millet cropping subject to extremely variable weather conditions. The main objectives were:to test and refine the hill scoring technique for characterizing within field soil and crop yield variability in 3 localities of western Nigerto identify soil properties explaining yield variability in space and timeto evaluate the effects on millet yield of site specific management of manure and fallow in a Fulani farmer's fieldto compare management systems used by farmers in four different landscape positionsto describe farmers methods of land evaluation and management options, based on farmers' expert knowledge of the environmentWithin-field soil and crop variability are discussed in chapters 2 and 3. Grain and straw yields varied considerably within-field at each of the three sites, and also between sites and between years. In 1996, grain yields varied from 8-383 kg ha -1, 2-1343 kg ha -1, and 7-815 kg ha -1at the three sites along a 400 km N-S gradient. The coefficient of variation at the three sites was 61, 55, and 53% respectively. Only 5 to 28% of the yield variability could be explained by soil chemical properties. Other factors such as micro-topography and water redistribution also made yields vary over short distances according to several studies in the region. A millet hill scoring method was tested and refined to obtain yield estimates before crop harvest. Scoring studies have remained at the row or plot level as opposed to the individual hill level. The method was simple and was able to explain up to 67% of the yield variation. Yield variation between years was least at the drier northern site with poorer soil and yields. Variation in yields among years was most closely correlated with soil pH and Al in the northern and central sites, whereas P was the best in explaining grain yield differences in the southern site.Chapter 4 deals with land management at the individual household level. Soil and crop management were investigated in two fields owned by a Fulani household. Management practices created man-made variability in the fields. Soil nutrient contents were improved in patches through the use of field corralling of livestock and fallow. Quantities of manure applied at specific sites varied from 1500 to 17000 kg ha -1. Corralling increased yields from 500 to 1100 kg ha -1, but amounts of manure applied were too high in some spots and losses were likely to occur through leaching. Nutrients and pH changes in the soil profile were found to change appreciably over time following the application of manure or of fallow. Based on the results obtained, an improvement in the farmer's management can be achieved by spreading manure to an area 3 to 5 times larger than the area actually used.Chapter 5 focuses on farmers' land management practices according to landscape position. Contrary to common belief, soils on the plateau were richer than soils on other landscape positions, which were cropped continuously and had a sandier texture. Plateaus, however, showed limitations such as low infiltration of rainfall and were located relatively far away from villages. Fields on undulating terraces and valleys had the highest number of different management practices, among which the use of livestock corralling and fallow were the most important.Chapter 6 considers social aspects of soil management, through the use of ethno-pedology by farmers in ordinary cropping activities. Farmers' knowledge of the land, plants and weather is described as well as the use of this knowledge by farmers in millet production. Simple soil descriptors such as texture, color, surface condition and indicator plants have been used by farmers to evaluate the land. Management practices rely on local knowledge regarding variability in soil fertility and water availability as a guide to implement crop management decisions and to design risk reducing strategies. These compensate in part for the lack of external inputs. The value of ethno-pedology for modern research is that it can serve to better identify farmers' needs and, as a result, improve research quality and the effective communication of results obtained. However, limitations in the use of ethno-pedology exist and they include its inability to quantify factors and the confusion between causes and effects for processes not well understood by farmers.</p

Use of a scoring technique to assess the effect of field variability on yield of pearl millet grown on three alfisols in Niger.

Within-field spatial variability of pearl millet (Pennisetum glaucum) was studied at three different sites on Alfisols in Niger. Grain yields in fields on a North-South gradient were 8-383, 2-1343, 7-815 kg/ha, with a coefficient of variation of 61, 55, and 53%, respectively. Variability was explained by soil chemical factors for only 5 to 28%. A simple method of scoring millet growth for individual hills a few weeks before harvest was tested by measuring yield variability in a field as an alternative for expensive soil chemical analyses. The median score value explained 25, 67, and 8% of the variability for the same gradient, respectively. As a verification step, map pattern comparisons of millet grain and straw yields with median score values gave low taxonomic distances (0.01-1.7), indicating significant similarities in variability. The hill scoring method is an appropriate tool to identify millet grain and straw yield variability

Fertility management and landscape position: farmers' use of nutrient sources in western Niger and possible improvements

Poor millet growth and yields in Niger are commonly attributed to rainfall deficits and low soil nutrient content. Land management by local farmers is done as a function of soil types, crops, and available resources. Farmer management practices in millet fields located on four different landscape positions were studied in a village in western Niger located near the 600 mm isohyet. Average distance from homestead to field was 980 m, with fields in the valley bottom much closer (average 225 m) and fields on the plateau much further (average 2300 m). Farmers considered the valley and plateau fields slightly more fertile than the other fields, but rainfall infiltration on plateau fields is often relatively poor. Nitrogen and phosphorus contents in the soil were highest on the less intensively cropped plateaus. More than 50% of the fields did not receive any applied nutrients other than during livestock grazing of leftover stover. Manure application was done through corralling in only four of the fields studied (20%), out of which three were farmed by Fulani using their own herds for manuring. There was no significant effect of landscape unit on yield, though yields in the valley and on the upper slope were slightly higher than average. Millet grain yields, soil carbon and soil phosphorus decreased significantly with distance from the living quarters. This may be because manuring usually takes place close to home (average distance in 1997 <200 m). Manure application increased millet grain production from 126 kg ha−1 to 316 kg ha−1 in 1997. Manuring yielded more than 1000 kg ha−1 in 1996, when rainfall was much more favourable. Fallowed fields yielded an average 143 kg ha−1 of millet grain in 1997, with fallow taking place an average of 1640 m from the homestead. Another soil fertility management practice included use of millet threshing residues in fields adjacent to the village. There was no chemical fertilizer application. Any improvement to the system will require the solution of existing constraints limiting the integration of livestock and crops and/or limiting the input of external sources of nutrients in Niger. These limitations can include lack of land to allow fallowing practices and/or grazing; local non-availability of mineral fertiliser; lack of capital to buy fertiliser, due in part to low millet prices; lack of means of transport for inputs; but also lack of means for pest control and lack of labour for sowing, weeding and thinning. Initial improvements may be made by making more efficient use of the available manure, through much lighter and slightly more frequent manuring of much larger area

Soil measurements during HAPEX-Sahel intensive observation period

This article describes measurements made at each site and for each vegetation cover as part of the soils program for the HAPEX-Sahel regional scale experiment. The measurements were based on an initial sampling scheme and included profile soil water content, surface soil water content, soil water potential, infiltration rates, additional measurements on core samples, and grain size analysis. The measurements were used to categorize the state of the surface and profile soil water regimes during the experiment and to derive functional relationships for the soil water characteristic curve, unsaturated hydraulic conductivity function, and infiltration function. Sample results for different supersites and different vegetation covers are presented showing soil water profiles and total soil water storage on days corresponding to the experimental ‘Golden Days’. Sample results are also presented for spatial and temporal distribution of surface moisture content and infiltration tests. The results demonstrate that the major experimental objective of monitoring the supersites during the most rapid vegetative growth stage with the largest change of the surface energy balance following the rainy season was very nearly achieved. Separation of the effects of probable root activity and drainage of the soil profile is possible. The potential for localized advection between the bare soil and vegetation strips of the tiger bush sites is demonstrate

Strategies to optimize allocation of limited nutrients to sandy soils of the Sahel: a case study from Niger, West Africa

Soils used for rainfed cereal production in Niger are sandy, deficient in major nutrients (N and P), and also low in organic matter content. Scarce rainfall with an unpredictable distribution in space and time makes crop and nutrient management difficult. Observations were made in 1996 and 1997 on management by a Fulani tribal household, based on manure application through corralling and on use of fallow. Field corralling of cattle left between 1.5 and 17 Mg ha(-1) of manure on limited areas of the fields. Millet grain yields were increased from 500 kg ha(-1) in areas manured 6 or more years ago to 1100 kg ha(-1) in recently manured areas. Drought during the growing season of 1997 limited the effects of manure application on grain and straw yields. Soil carbon and nitrogen levels were higher at depths below 0.20 m in sites where manure was applied 4-5 years ago (W), while pH and P were higher in 0-0.10 m of the soil profile in practices where manure was applied the same year (M0). Nutrient management in 1997 could have been improved by reducing the locally very high manure rates in order to fertilize a two or three times larger area and consequently improve yields over a larger area and reduce risks of nutrient leaching and crop damage from droughts. (C) 2002 Elsevier Science B.V. All rights reserved

Strategies to optimize allocation of limited nutrients to sandy soils of the Sahel: a case study from Niger, West Africa

Soils used for rainfed cereal production in Niger are sandy, deficient in major nutrients (N and P), and also low in organic matter content. Scarce rainfall with an unpredictable distribution in space and time makes crop and nutrient management difficult. Observations were made in 1996 and 1997 on management by a Fulani tribal household, based on manure application through corralling and on use of fallow. Field corralling of cattle left between 1.5 and 17 Mg ha(-1) of manure on limited areas of the fields. Millet grain yields were increased from 500 kg ha(-1) in areas manured 6 or more years ago to 1100 kg ha(-1) in recently manured areas. Drought during the growing season of 1997 limited the effects of manure application on grain and straw yields. Soil carbon and nitrogen levels were higher at depths below 0.20 m in sites where manure was applied 4-5 years ago (W), while pH and P were higher in 0-0.10 m of the soil profile in practices where manure was applied the same year (M0). Nutrient management in 1997 could have been improved by reducing the locally very high manure rates in order to fertilize a two or three times larger area and consequently improve yields over a larger area and reduce risks of nutrient leaching and crop damage from droughts. (C) 2002 Elsevier Science B.V. All rights reserved

Fertility management and landscape position: farmers' use of nutrient sources in western Niger and possible improvements

Poor millet growth and yields in Niger are commonly attributed to rainfall deficits and low soil nutrient content. Land management by local farmers is done as a function of soil types, crops, and available resources. Farmer management practices in millet fields located on four different landscape positions were studied in a village in western Niger located near the 600 mm isohyet. Average distance from homestead to field was 980 m, with fields in the valley bottom much closer ( average 225 m) and fields on the plateau much further ( average 2300 m). Farmers considered the valley and plateau fields slightly more fertile than the other fields, but rainfall infiltration on plateau fields is often relatively poor. Nitrogen and phosphorus contents in the soil were highest on the less intensively cropped plateaus. More than 50% of the fields did not receive any applied nutrients other than during livestock grazing of leftover stover. Manure application was done through corralling in only four of the fields studied (20%), out of which three were farmed by Fulani using their own herds for manuring. There was no significant effect of landscape unit on yield, though yields in the valley and on the upper slope were slightly higher than average. Millet grain yields, soil carbon and soil phosphorus decreased significantly with distance from the living quarters. This may be because manuring usually takes place close to home ( average distance in 199