Macro- and Micronutrient Uptake in Rice + Cowpea Production System as Influenced by Mineral Nitrogen and Crop Population
The study was aimed at evaluating macro- and micronutrient uptake of rice and cowpea when grown in sole and mixture populations under varying levels of density (5x 10 4 , 10x 10 4 and 20 x10 4 plants/ha) and nitrogen (0,15,30 and 45kgN/ha), using urea as nutrient source. Results obtained showed that uptake of nitrogen increased with increasing rates of nitrogen fertilizer in both crops used for the study. In both sole and mixture populations, 45kgN/ha (50000plants/ha) and 30kgN/ha (200000plants/ha) recorded the lowest nitrogen uptake value of 0.12 and 0.14mg/plant respectively. Mean P uptake in the second in the cropping was reduced by 35.3% over the first cropping. Medium density of 100000plants/ha gave the highest K value of 0.45mg/ha during the first cropping. Uptake of potassium, phosphorus, sodium, calcium and magnesium and microelements were generally higher in cowpea than rice. Values of zinc uptake in shoots of both rice and cowpea were very low ranging from 0.00002 to 0.000075mg/plant in rice and 0.00011 and 0.0017mg/plant in cowpea. Increasing plant population density generally depressed uptake of both macro- and microelements in both rice and cowpea. Results from this study indicate that the high plant densities reduce nutrient uptake of crops, hence farmers should select optimum densities that will maximize crop nutrition and consequently yield. Keywords: nutrient uptake, cowpea, rice, nitrogen fertilizer, plant population