Effects of nitrogen fertilizer application and solar radiation on thegrowth response of sorghum seedlings to soil moisture [Japanese]

摘要

The effects of nitrogen fertilizer application and solar radiation on the growth response to soil moisture were examined in sorghum seedlings grown in culture boxes. The effects of soil moisture (f) and amount of nitrogen fertilizer application (g) on the increment of total dry matter weight of sorghum seedling (DeltaW) were represented satisfactorily by the following reciprocal equation, 1/DeltaW=A/(f- f(0)) + B(g+g(0))/(f-f(0)) + C/[(f-f(0)) (g+g(0))] + D/(g+g(0)) + E, where f(0) and g(0) were the uppermost value of unavailable soil moisture and the amount of nitrogen supplied from soil and seeds. A, B, C, D and E were coefficients. The effects of soil moisture (f) and solar radiation (S) on DeltaW were expressed approximately by the following reciprocal equation, 1/DeltaW=A/(S-S-0) + B/(f-f(0)) + C(f-f(0)) + D, where S-0 was the daily compensation point. These results indicated that the effects of solar radiation and soil moisture are additive, but the interaction between soil moisture and nitrogen fertilizer is not negligible. The transpiration efficiency was unaffected by soil moisture, nitrogen fertilizer and solar radiation.