Availability of Residual and/or Applied Inorganic Phosphorus for Sugarcane Uptake and Growth in a Post-Mined Reconstituted Soil

Abstract

Mineral sands mining is worldwide an environmental issue and also at the Hillendale mine in KwaZulu-Natal, South Africa. The post-mined soil is to be rehabilitated to sugarcane cropping. One of the concerns with the post-mined soil which is reconstituted with a 70:30 mixture of sand: slimes (silt-plus-clay fraction), is its low phosphorus (P) status, which could be limiting for optimum sugarcane production. A field experiment was conducted on a reconstituted soil at Hillendale to establish the availability of either residual or applied inorganic P to the plant and first ratoon sugarcane crop. Four treatments were evaluated including those where P fertilizer was omitted, applied at half the recommended rate or introduced equal to the recommended rate according to chemical analysis of the soil. In the fourth treatment, no fertilizer was applied at all, whereas nitrogen (N) and potassium (K) were added at recommended rates in the first three treatments. Phosphorus application had a significant effect on sugarcane fractional light interception and aboveground biomass yield of the plant and first ratoon crops, and stalk length and diameter of the first ratoon crop. Pol, brix, purity and fibre content and tiller number were not affected by P application. The application of P increased the foliar N, P, K, calcium (Ca), magnesium (Mg) and sulphur (S) contents of both crops. However, foliar N, P and K were deficient in the first ratoon crop even in the case where fertilizer was applied at the recommended rates, which could have been because of waterlogging. The possible effect of waterlogging on P uptake needs to be addressed in future studies in this reconstituted soil.