Sidedress Nitrogen Application Rates to Sorghum lntercropped with Tropical Perennial Grasses

Intercropping sorghum [Sorghum bicolor (L.) Moench] with tropical perennial grasses and using the appropriate rate of sidedress N application can maximize grain yield (GY) and revenue and can improve land-use efficiency (LUE). The effects of monocropped sorghum (MS) or sorghum intercropped with palisadegrass (Urochloa brizantha cv. Marandu; SPG) or guineagrass (Panicum maximum cv. Mombasa; SGG) and sidedress N application rates of 0, 50, 100, and 200 kg ha(-1) on leaf 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 lower 1000-grain weight, shoot dry matter, and GY than MS and SPG at all sidedress 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) and crude protein of tropical perennial grasses were higher as a function of the sidedress N rate. The SGG treatment resulted in negative net profits for all sidedress N rates. The MS and SPG treatments (independent of sidedress N rates) resulted in similar net profits (approximately US$85 and 560 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.