Core Ideas Pearl millet and cowpea intercrop production is important in the Sahel. Inadequate nutrient supply constrains crop growth. Pearl millet sole crop nutrient response information is applicable for intercropping. Application of N and P to intercrop compared to sole crop has more profit potential. In the Sahel, crop production is dominated by pearl millet [Pennisetum glaucum (L.) R. Br.] cropping systems including intercropping with cowpea [Vigna unguiculata (L.) Walp]. The research objectives were to determine pearl millet sole crop (PMSC) and intercrop nutrient response functions, profit opportunities from fertilizer use, and a means of relating intercrop to PMSC response. Pearl millet–cowpea trials were conducted in Niger and Mali. The treatment structure was an incomplete factorial with five, four, and four levels of P, N, and K, respectively. Response functions were determined for intercropping with cowpea yield converted to a pearl millet grain yield equivalent for ratios of cowpea to pearl millet grain value (CpPm) ranging from 1 to 5 kg kg−1. Response functions were also determined in consideration of fodder value. A method of adjusting PMSC response coefficients with CpPm as the independent variable was developed for determination of intercrop response functions. Yields and responses to nutrients were low but adequate for profitable N and P use. Value of intercrop production ranged from 50 to 125% more compared with PMSC for CpPm of 2 and 4, and the respective response to 10 kg ha−1 P was 28 and 135% more with intercrop. Consideration of fodder added 23% to the yield value. Application of N and P for intercrop compared with PMSC production has much more profit potential. The ability to apply PMSC functions in determination of pearl millet–cowpea responses to applied nutrients offers a means to improve fertilizer use for the intercrop.
This chapter explores alternatives of nutrient supply and management for high nutrient use efficiency. It establishes that fertilizer use optimization is within the framework of integrated soil fertility management with recommended fertilizer rates adjusted according to soil property information and the use of complementary practices in sub-Sahara Africa.
Core Ideas Applying N for maize production in semi‐arid west Africa can be profitable.The profit potential of N application is great for maize–groundnut intercrop.Application of P and K has low and inconsistent profit potential for maize production in semi‐arid west Africa.Nutrient response functions can be determined for maize–groundnut intercrop from maize sole crop data. Maize (Zea mays L.) is important in semiarid West Africa where the increase in demand exceeds the increase in production. Yield is often constrained by inadequate nutrient availability even though the occurrence of soil water deficits may overall be more constraining. Research was conducted in semiarid Mali and Niger to determine the yield and profit responses of maize sole crop (MzSC) to N, P, and K and to develop a procedure for determining maize–groundnut (Arachis hypogaea L.) intercrop (MzGnI) nutrient response functions from MzSC functions. Trials were conducted in 2014 and 2015 at five locations spanning 14 degrees of longitude and two degrees of latitude. Mean MzSC grain yield increase due to 50 kg ha−1 N was 0.69 Mg ha−1 in Mali and 0.42 Mg ha−1 in Niger, and due to 10 kg ha−1 P was 0.14 Mg ha−1 in Niger with inconsistent P effects in Mali. Responses to K were negligible. Productivity and profit potential with N application was more with MzGnI compared with MzSC, but profit potential for applied P and K were not improved with MzGnI. Considering the fodder value of stover added to production value but did not have much effect on profits from fertilizer use. The procedure for determining MzGnI nutrient response functions by adapting MzSC functions was developed, providing a means to improve fertilizer use efficiency for MzGnI. Productivity and returns to applied N, on a maize grain value equivalent, are greater with MzGnI compared to MzSC.
Sorghum–groundnut intercropping is agronomically and economically important in West Africa. Intercrop nutrient response functions are needed to maximize profit from fertilizer use. Intercrop response functions can be estimated from sole crop responses. Sorghum (Sorghum bicolor L. Moench)–groundnut (Arachis hypogaea L.) intercropping is important in the Sahel and Sudan Savanna. Nineteen trials were conducted during 2014 and 2015 in Mali and Niger for determination of: response functions for sorghum sole crop (SSC) and intercrop to N, P, and K; effects of the P×N interaction and of a nutrient package for diagnosis of other deficiencies; and a procedure for estimation of intercrop functions from SSC response functions. Six Niger on‐station trials included treatments for determination of intercrop effects on sorghum yield and response. Mean grain and fodder yield increases for SSC were, respectively, 18.8 and 17.6% with 10 kg ha−1 P, 30.7 and 18.8% with 30 kg ha−1 N, and 0 and 6.8% with 10 kg ha−1 K applied. The diagnostic treatment increased grain yield for only 1 of 19 site‐years (SYs). Sorghum grain yield was 30% less with intercropping compared with SSC for 2 of 6 SY but 11% less overall. Overall, sorghum fodder yield was 23% more with intercropping. Sorghum response to P was 86% greater for SSC compared with intercrop. With intercropping, groundnut pod yield exceeded sorghum grain yield. The value of intercrop production was higher than for SSC. Fodder added 23 and 30% to the value of SSC and intercrop harvests, respectively. Equations were developed for determining optimal nutrient rates and intercrop response functions from SSC functions. Fertilizer applied to the intercrop compared with SSC has much more profit potential for this part of West Africa.
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