Effects of nitrogen application on yield and forage quality of grain and forage maize

Influences of different nitrogen application rates (N1:0 kg·ha-1, N2:100 kg·ha-1, N3:200 kg·ha-1, N4:400 kg·ha-1) on yield and forage quality of grain-forage maize which were planted in furrows of completely mulched in rainfed agriculture regions in the Loess plateau were investigated. The results showed that leaf area index (LAI), dry weight of leaf, leaf sheath and stalk, grain yield and biomass increased with the increasing of nitrogen application rate with the same rates of phosphorus (P) and potassium (K) applications. Contents of neutral detergent fiber(NDF) and acid detergent fiber(ADF) decreased with the increasing of nitrogen application rate, but increased with crop development. Content of crude protein performed increased with the increasing of nitrogen application rate, but decreased with the crop growth development. Content of NDF and ADF in the leaves were lower than those of leaf sheath under the same nitrogen rate. The quality of grains was also benefited from higher nitrogen application rates. Therefore, it can be concluded that optimum nitrogen fertilizer application can improve yield and quality of grain-forage maize and 300 kg·ha-1 of N was the optimum rate for maize growth in furrows of completely mulched alternating narrow and wide ridges systems, in semiarid areas in the Loess Plateau.