Fate of basal N and growth of crops cultivated under cassava-based intercropping system with reference to K application rate

Abstract

Cassava is the fourth most important staple food crop in Asia and main crop in the cropping systems used in upland areas. Among staple crops, cassava most abundantly absorbs potassium (K), suggesting that a nutrient disorder might occur among the intercrops. A nutrient disorder in intercrops may affect the fate of applied nitrogen (N) through the growth of intercrops. Strong K-absorption ability of cassava can be potentially antagonistic to other crops. If so, when the soil K level is critical in an intercropping system, K application may result in increased yield through mitigation of the K antagonism among intercrops, accompanied with nutrition improvement of other nutrients. We conducted a field experiment to evaluate the growth of crops and the fate of N fertilizer with reference to the application rate of K in a cassava-based cropping system in South Sumatra. The results obtained were as follows: 1) The dry weight values and yield of cassava, upland rice, and corn without K application were lower than those with K application treatment. However, no significant differences in the dry weight and yield of these crops were observed between K application treatments of standard and double dose. 2) The recovery rate of basal N by upland rice and cassava was positively related to the yield of each crop. Amount of immobilized N in soil applied to upland rice was not affected by the application rate of K. 3) Total recovery rate of basal N applied to upland rice was 2 times higher in the K application treatment than without K application treatment. It appears that K application alleviated the N pollution problem by inducing a high uptake rate of N fertilizer by crops.