Regulation of Density and Fertilization on Crude Protein Synthesis in Forage Maize in a Semiarid Rain-Fed Area

Density and fertilization mode are the key factors regulating crude protein synthesis in forage maize; however, there is a lack of systematic understanding regulation mechanism. Here, nitrogen/potassium ratio (N/K), free amino acid (AA) content, enzyme activities (nitrate reductase (NR), glutamine synthetase (GS) glutamic pyruvic transaminase (GPT)) content yield leaves, stems, grain maize, as well relationships among them, were explored. The results showed that N/K DL-40 (60,000 plants per ha−1, 40% N topdressing at large trumpet stage) DH-50 (75,000 50% significantly increased grain, correspondingly, NR, GS, GPT NR delayed decline AA content. After tasseling, for by 74.1% 39.8% respectively, 19.9% 25.6% 16.7% 35.2% 23.5% 25.9% respectively. There significant quadratic parabolic with proportion topdressing. was relationship activity stems grain. Regulating adjusting density can improve maize. Treatments increasing plant N/K, but slowed decrease