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华北土壤普遍缺乏氮肥及有机质。豆科绿肥为补充土壤氮素及有机质方法之一。但华北旱田鲜有实行绿肥者。同时中央农业实验所在陕西关中区举行之绿肥肥料试验及绿肥示范,其结果并未充分表现绿肥之效能,有时绿肥完全无效,有时绿肥尚能增加作物之产量,但其增加之产量远逊于南方绿肥之效果。华北绿肥效果不大之原因何在,颇值研究。中央农业实验所北平农事试验场于民国卅五年至卅六年间曾举行小麦绿肥试验,于卅元年夏播种绿豆,八月下旬压青,十月初播种小麦。于绿肥压青前后及小麦生长期间,定期测定土壤水分及硝酸氮含量,比较夏闲区与绿肥压青区之硝酸氮含量,研究绿肥压青对于硝酸氮含量之影响。兹将所得结果略述于后。
North China soil generally lack of nitrogen and organic matter. Legume green manure is one of the methods to supplement soil nitrogen and organic matter. However, the practice of green manure in northern China rarely occurs. At the same time, the experiment of Green Manure Fertilizer and Green Manure Demonstration held by Central Agricultural Experiment Institute in Guanzhong District of Shaanxi Province did not show the performance of green manure. In some cases, green manure was completely ineffective. Sometimes, green manure could increase the yield of crops, but its yield was far less than that of South China The effect of green manure. North China green manure is not the reason why, rather value research. The Peking Agricultural Experiment Station of the Central Agricultural Experiment Station held a green manure experiment in the Republic of China five to six years ago. Mung beans were sown in the first summer of the year, pressed into the green in late August and sown in early October. The soil moisture and nitrate nitrogen content were measured periodically before and after green manure depressing and wheat growing. The nitrate nitrogen content in summer and green manure depressing areas was compared to study the effect of green manure depressing on nitrate nitrogen content. The results will be summarized in the post.