【摘要】 本文用¹⁵N示踪法在温室条件下,研究紫云英植株上不同器官组成的标本和尿素的肥效;着重讨论绿肥的氮素有效度问题。1.以水稻的分蘖动态作为绿肥N有效度的定性指标;2.用C∶N预估绿肥N对当季水稻的有效度未能得到满意的效果,但是它同后作蕹菜在淹水栽培下吸取的氮量之间的相关性却很高,并分析其原因;3.多元回归与相关的分析结果指出,提高绿肥N有效度要求高氮又高碳和低C∶N比;4.讨论了有关增加紫云英肥效的一些农业措施问题。更多还原

【Abstract】 An experiment was carried out in the green house to study the N recovery of various parts of milk-vetch and fertilizer urea which were labelled with ¹⁵N. Except fertilizer urea which had the highest recovery of N in the first rice crop and the least in the succeeding crop of Wengcai（Ipomoca aqnatica forsk）, the recovery of N from various parts of milk-vetch depends upon the metabolic function during the life span.The nitrogen availability index of green manure has been discussed. The extent to which the rice tillers developed depends greatly on the supply of N. Thus, the tillering potential of rice can be used as a qualitative indexof the N supply from green manure.Having made an analysis by simple and multiple correlation and regression, we discussed the validity of the C/N ratio used as a quantitive indexof the N efficiency of green manure. It was pointed out that the use of C/N ratio as an index showing the N availability during the first rice crop was unsatisfactory. However, the relation of the recovery of N from greenmanure to its C/N ratio brought out some new aspects. The"priming effect" of soil nitrogen was negative and the N recovery shifted very little nearthe asymptote when the ratio was greater than 16. 7. When the C/N ratio of green manure is close to that of the soil, a positive value of the"priming effect"was obtained and a maximum ultimately reached, then the recoveryof N green manure rapidly increased. The residual effect of green manure for the succeeding crop can be predicted from its C/N ratio. The correlation coefficient was highly significant.The analysis by partial and multiple correlation and regression modified the outcome obtained by those of simple correlation and regression with a result leading to an empirical equation relating the N availability of green manure to its N and C content Some agricultural practices to increase the fertilizer efficiency of green manure were suggested.更多还原