Integrated management of composted cattle manure and mineral fertilizer for improved pearl millet and cowpea yields under strip cropping system in Niger

Soil fertility decline due to low nutrient input is a constraint to increasing crop production in smallholder cropping systems in Niger. The current rate of fertilizer application is insufficient for replenishing soil fertility and to compensate for nutrient removal. Organic amendments provide most of the essential nutrient elements, but limited availability and contrasting qualities restrict the supply of sufficient quantities to meet crop demand. This study therefore aimed at enhancing the yields of improved pearl millet and cowpea through the sole and integrated use of compost and mineral fertilizer. Compost was prepared using manure and cowpea haulm. Decomposition and nutrient release patterns of the matured compost were monitored under field conditions using litterbags. The optimum combinations of compost and mineral fertilizer for optimal millet and cowpea yields were assessed over a two-year field experiment during the 2013 and 2014 cropping seasons. The treatments used consisted of a factorial combination of (i) three levels of compost (0, 2500 and 5000 kg ha-1) and (ii) four levels each of two mineral fertilizer types (0, 100, 175 and 200 kg ha-1 NPK for millet and 0, 50, 75 and 100 kg ha-1 DAP for cowpea). The treatments were arranged in Randomize Complete Block Design (RCBD) with three replications. Composting manure resulted in 2.5 and 4.5 times more N and P contents respectively. Decomposition results after 84 days revealed that 40.3 and 56.5 % of compost mass losses were recorded respectively in 2013 and 2014 cropping seasons. In 2013, 31, 74 and 97 % of N, P and K, respectively were released at 63 days of decomposition. On the other hand, peak N, P and K release values of 58, 60 and 99 % respectively were obtained after 84 days of decomposition under field conditions in 2014. The application of 2500 kg ha-1 of xviii compost resulted in an increase of pearl millet and cowpea grain yields of 11 and 26 %, respectively over the 2 cropping seasons compared to the application of recommended rate of mineral fertilizer. Doubling the rate of compost from 2500 to 5000 kg ha-1 did not result in any additional increase in yield of millet and cowpea. Combined use of compost and mineral fertilizer markedly improved some millet and cowpea growth parameters (crop growth rate and leaf area index) which resulted in an increase in grain and straw/haulm yield. Sustainability yield index (SYI) was greatest on plots which received the combined application of compost and mineral fertilizer. Application of compost at 2500 kg ha-1 + 175 kg ha-1 NPK and 5000 kg ha-1 + 175 kg ha-1 NPK which produced higher SYI values of 0.64 and 0.65 respectively, appeared to be more promising in sustaining millet production. Similarly, application of 5000 kg ha-1 compost combined with 50 and 75 kg ha-1 DAP gave higher cowpea SYI of 0.63 and 0.57 respectively. Combined application of compost and mineral fertilizer led to N and P accumulation in the soil which resulted in positive partial N and P balances. On average, N and P use efficiencies for millet were increased by 60 and 31 %, respectively with the application of compost at 2500 kg ha-1 + 175 kg ha-1 NPK over the control. The highest N and P use efficiencies of cowpea were recorded on plots that received compost at 2500 kg ha-1 + 50 kg ha-1 DAP. Among all the combined use of compost and NPK fertilizer, application of 2500 kg ha-1 compost + 175 kg ha-1 NPK gave the highest net return of US $ 366.3 for pearl millet while the highest cowpea net return of US $ 37.5 was obtained under 2500 kg ha-1 compost + 50 kg ha-1 DAP . These findings indicate that pearl millet and cowpea yields could be increased with combined use of compost and mineral fertilizer which may have important implications for combating food insecurity in the Sahel region.

Source: KNUST