On-farm spatial and temporal variability of soil and water in pearl milletcultivation

Crust-prone sandy soils of low fertility, combined with unreliable and erra tic rainfall, affect spatial variability of crop growth in the Sahel. We hy pothesized that spatial variability in soil properties and soil water conte nt on a hillslope stale affected pearl millet [Pennisetum glaucum (L.) Br.] yields. We focused on the effects of trust development, micro topography, rill distribution, and soil nutrients on crop yield variability within and between gears (1994-1996) in a farmer's field in semi-arid Niger. Yields in plots of 15 by 6 m varied within a year by a factor of 46 for nonfertilize d millet (27-1249 kg ha-L), and by a factor of 16 (76-1213 kg ha(-1)) for f ertilized millet. Despite this variation, a linear yield gradient was obser ved along the 300-m-long field with a gentle 1 to 3% slope. Grain yields de creased 0.5 kg ha(-1) for nonfertilized millet and 1 kg ha(-1) for fertiliz ed millet per meter along the slope when moving from the bottom to the top of the field. Soil water availability varied greatly, with individual neutr on probe access tubes (36 tubes on an 8-ha field) presenting a percent infi ltration ranging from 15 to 182% of rainfall for individual rainstorms. Ups lope had significantly lower percent infiltration (75%) than both midslope (90%) and downslope (84%). Between years, soil water and nutrients alternat ed in limiting crop growth, depending on rainfall distribution (annual rain fall ranging from 488-596 mm). However, in all three years toposequence rel ated factors dominated yield variability and caused similar yield gradients along the slope.