Soil Tests as a Means of Predicting Response of Rape to Added N, P, and K1

Soil tests were evaluated as a means of predicting response of rape to added N, P, and K in 23 field experiments on non‐fallowed soils from 1961 to 1969. Nitrate‐N content to a depth of 61 cm, NaHCO3‐extractable P, and NH4OAc‐extractable K of soils were found to be useful in predicting yield response of rape to added N, P, and K. Rape responded to added N when NO3‐N in the soil to a depth of 61 cm was >100 kg/ha, responded to added P when soils had NaHCO3‐extractable P <10 ppm, and responded well to added K when soils had 35 or less ppm of NH4OAc‐extractable K.