氮肥追施量对玉米秸秆营养价值的影响

用目前生产中普遍种植的青饲玉米品种白马牙（Zea mays L．）的秸秆为试验材料，通过化学成分分析、活体外消化率测定、活体外发酵产气量测定和羊的饲养试验，研究了氮肥施肥量（尿素0、150、300、450kg／ha）对玉米秸秆营养价值的影响。结果表明：随着追施尿素量的增加，氨基酸总量、非必需氨基酸总量和粗蛋白、真蛋白、各种必需氨基酸、Ca含量呈直线规律提高（P〈0．001），而粗脂肪和ADF含量则均不受影响（P〉0．05）；追施尿素低于300kg／ha时，总糖含量不受尿素量的影响，尿素量高于300kg／ha时，总糖含量则随尿素量的提高而减少。追施尿素能够提高（P〈0．001）玉米秸秆活体外DMD、CPD、NDFD和ADFD，并且，各项消化率指标随尿素量的提高也呈直线规律提高（P〈0．001），但尿素量超过300kg／ha时，这种作用效果不再提高。用不同尿素追施量的青贮玉米秸秆饲喂大尾寒羊羔羊，羔羊增重、饲料转化效率和经济效益随施肥量的提高而提高，其中，以尿素量为300kg／ha时效果最好。可见，追施氮肥不仅能够改变玉米秸秆的化学成分含量．而且能够提高玉米秸秆的营养价值。

Effect of Application Level of N-fertilizer on Nutritional Values of Corn Stalks

Corn stalks from Zea mays L,were served as experimental material to study the effects of N-fertilizer(urea 0,150,300,450 kg/ha) on the nutritional value by using chemical analysis,in vitro two-stage digestion,in vitro gas production and sheep feeding trial.The results showed that the corn stalks had a linear(P<0.001) increase in the contents of CP,true protein,amino acids,nonessential amino acids,essential amino acids and Ca as quantity of urea fertilized increased,and total saccharide content did not change with urea under(300kg/ha) and had a negative linear correlation with urea above 300kg/ha.N-fertilizer had little or no effect on EE,ADF content of corn stalks.The in vitro digestibilities of DM,CP,NDF and ADF of corn stalks increased(P<0.01) in a linear(P<0.001) with the application of N-fertilizer,but when urea dose was upon 300kg/ha,the function was not enhanced.Daily gain,feed conversion and economic return increased after the lambs(Fat-tailed Han-yang) were fed the silage of the corn stalks fertilized with urea.When corn plants were fertilized with urea 300kg/ha,the result of feeding was the best.In conclusion,the contents of chemical components of corn stalks were alternated,and moreover,nutritional value of corn stalks was increased after corn plants had been applied with N-fertilizer.