Phosphorus Transformations in Alternately Flooded California Soils: I. Cause of Plant Phosphorus Deficiency in Rice Rotation Crops and Correctional Methods

Abstract

AbstractRice (Oryza sativa L.) is widely grown on soils continuously submerged during the annual growing season. Upland crops following rice culture often exhibit chlorosis, extremely slow growth, and low productivity. Phosphorus deficiency induced by drainage following soil submergence was shown to exist in crops following rice. Experiments were conducted to clearly define the problem in terms of crop response to P fertilizer on major California rice soils and to determine the most efficient methods of P fertilization.Three field experiments were conducted on Myers, Willows, and Sacramento soils following variable years of annual rice production. Wheat (Triticum aestivum L.) or barley (Hordeum vulgare L.) were fertilized with P rates of 0, 29, 59, and 89 kg/ha applied as band‐placed TSP, broadcast TSP and band‐placed MAP. Phosphorus sources, rates, and method of application were evaluated by plant responses including seedling dry matter, plant total‐P and 2% HAc extractable PO4‐P, plant total‐N, grain yield, and 1,000‐kernel weight.The differential severity of plant P deficiency between the three soils was Myers ⩾ Willows > Sacramento series. Severe plant P‐deficiency was observed in the Myers soil even though the soil NaHCO3‐extractable P level was 16.8 ppm. Soil submergence and drainage‐induced soil P transformations decreased soil P availability to wheat and barley following flooded rice.The relative efficiency of P fertilizer sources and methods was band‐placed MAP > band‐placed TSP > broadcast‐incorporated TSP. Phosphorus band‐placed 3 cm directly below the seed was more efficient than broadcast‐incorporated P in wheat and barley after rice. Band‐placed P resulted in greater P uptake by plants probably because of less soil sorption of fertilizer P and greater P availability relative to broadcast‐incorporated P.