Sidedress nitrogen application rates to sorghum intercropped with tropical perennial grasses

Intercropping sorghum [Sorghum bicolor (L.) Moench] withtropical perennial grasses and using the appropriate rate of side dress N application can maximize grain yield (GY) and revenue and can improve land-use efficiency (LUE). Th effects of monocropped sorghum (MS) or sorghum intercroppedwith palisadegrass (Urochloa brizantha cv. Marandu; SPG)or guineagrass (Panicum maximum cv. Mombaça; SGG) andsidedress N application rates of 0, 50, 100, and 200 kg ha–1 onleaf nutrient concentration, sorghum GY, revenue, and LUE were investigated during three growing seasons at Botucatu, SP,Brazil, on a clay, kaolinitic, thermic Typic Haplorthox. The SGG treatment had lower leaf N, P, and K concentrations and lower1000-grain weight, shoot dry matter, and GY than MS and SPGat all side dress N rates; MS and SPG at 200 kg ha–1 of sidedress N resulted in greater sorghum GYs (3.80 and 3.81 Mg ha–1,respectively). The forage dry matter production (FDMP) andcrude protein of tropical perennial grasses were higher as a function of the sidedress N rate. The SGG treatment resulted innegative net profits for all sidedress N rates. The MS and SPG treatments (independent of sidedress N rates) resulted in similarnet profits (approximately US$85 and $60 ha–1, respectively).The SPG treatment using 200 kg ha–1 of sidedress N resulted in a higher land equivalent ratio and relative N yield (1.27 and 123%,respectively) than SGG (0.96 and 107%, respectively). The SPG treatment with 200 kg ha–1 of sidedress N is the best option for increasing sorghum GY, revenue, and FDMP from autumn to part of the spring and for improving LUE.