Responses of Lolium perenne and Agrostis tenuis to phosphate and other nutritional factors in the reclamation of colliery shale.
In an NPKCa factorial experiment with L. perenne cv. S23 and A. tenuis cv. American Highland Bent on 5 colliery shales, P was deficient on all 5 substrata but a response to N was found only on the less acid shales. Response to P was correlated with various chemical estimates of soil P status, but good correlation was obtained only where both buffering capacity and quantity were taken into account. The P application required on each shale to give highest herbage yields was determined by yield curve experiments in a glasshouse and in the field; the correlation between field and glasshouse values was high. The equations giving best fit were: P requirement (kg/ha) = 16.57 - 2.82 X1 + 8.91 X2 for L. perenne and 32.02 - 2.84 X1 + 5.30 X2 for A. tenuis, where X1 = bicarbonate-soluble P (kg/ha) and X2 = phosphate buffering capacity at 10 mu mol/l (kg/ha). These equations accounted for 99 and 86%, respectively, of the variation in requirement.