Klaij, M.C. and Vachaud G., 1992. Seasonal water balance of a sandy soil in Niger cropped with pearl millet, based on profile moisture measurements. Agric. Water Manage., 21:313-330. In the Sahel, calculation of the field water balance from neutron-probe measurements is often difficult for pearl millet (Pennisetum glaucum (L.) R. Br.), which is due to the rapid drainage (D) of the sandy soils, on which it is typically grown. We present a simple method of calculating D in these soils from weekly neutron-probe data, The method divides the water balance into two phases. In the first, applicable early in the season, water flux across the maximum depth of probe measurement (Zm) is assumed negligible, and evapotranspiration (E) and D are calculated from the change in soil water content (0) between the bottom of the rootzone (Zr) and Zm, thus allowing calculation of unsaturated hydraulic conductivity, K(O), from the flux across Zr. In the second phase, when soil water starts to percolate across Zm, D is calculated from K(O), assuming a hydraulic head gradient of-1. The method is used to calculate a onedimensional water balance of a pearl-millet crop grown in a deep sandy soil at two fertility levels during a season of normal rainfall. Results show that the calculated K(0) functions compare well with those based on laboratory measurements. An acceptable estimate of drainage, and therefore E could be made. Mean cumulative E and D were, respectively, 211 and 207 mm for the unfertilized crop, and 268 and 148 mm for the fertilized crop with 440 mm of rainfall received during the crop cycle. The fertilized millet crop water balance was simulated, which compared to the calculation method resulted in an about 10% higher seasonal E and a 10% lower seasonal D. Our study shows that E can be corrected for D using a simple but accurate method, and consistent with other studies in the region indicates that rainfall is usually not the primary, limiting factor to pearl-millet production.
A bstract A field study was conducted over a 4-year period in Niger, West Africa, to determ ine th e effects of crop residue (CR), fertilizer, or a combination of crop residue and fertilizer (C R F) on yields of pearl millet (Pennisetum glaucum [L.] R. Br.). Despite a decline in yields of control plots (initial yields w ere 280 kg grain ha~J declining to 7 5 k g grain h a-1 over 4 years), yields of fertilizer plots were m aintained at 800-1,000 kg grain h a-1. Continued application of. CR slowly augm ented yields to levels similar to those of the fertilized plots. The effects of CR and fertilizer were approxim ately additive in the C RF plots. Addition of C R 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 higher soil pH and lower A1 saturation than did the fertilized treatm ents. R eturn of C R to the soil resulted in significantly reduced export of most plant nutrients, especially Ca, Mg, and K.
SummaryThe after effects of three years' continuous cropping with sole millet, sole cowpea or a traditional millet/cowpea intercrop were compared using five levels of nitrogen fertilizer. The continuous sole cowpea system had reduced the carbon to nitrogen ratio more than the continuous sole millet or the traditional intercrop. The test crop millet yielded much more, and its uptake of nitrogen and phosphorus was greater, when it followed sole cowpea than when it followed sole millet or the traditional millet/cowpea intercrop. The three years' continuous sole cowpea had an effect equivalent to the application of 205 kg N ha−1 on the test crop of millet. It also caused the greatest reduction in Striga infestation in the test crop. It is therefore recommended that cowpea cultivation be increased in the Sahel.
SummaryPearl millet is a staple cereal cultivated mainly by subsistence farmers on 14 million ha of the West African semi-arid tropics. Increasing pressure on the land has reduced the length of the fallow periods, which are necessary to restore soil fertility, resulting in declining yields. To investigate ways of reversing this decline, three systems combining phosphorus fertilizer application, improved varieties of millet and cowpea, and improved agronomic practices were compared with the traditional millet–cowpea intercrop system in a three year experiment. The most productive system involved the rotation of fertilized millet and cowpea. Pre-sowing tillage increased hay and fodder yields in all the improved systems. The application of fertilizer increased the amount of available phosphorus in the soil. Soil pH declined somewhat in all treatments, although the initially low soil organic matter did not change.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.