Sulfur and the Production of Rice in Wetland and Dryland Ecosystems
Rice (Oryza sativa L.) is one of few crop species that can be productively grown in both wetland and dryland conditions. Yields of rice may have to rise by 40 to 60% over the next 20 to 30 yr because of the demand from increasing population. The requirement for sulfur will rise by a comparable level, and unless fertilizer inputs increase, more sulfur deficiency can be expected, threatening the attainment of yield targets. Management of the sulfur nutrition of rice varies depending on whether the soil is submerged throughout the crop cycle as in paddy cultivation, aerated in the root zone as in upland production systems, or intermittently flooded as in rain-fed lowland, aerobic, and water-deficit irrigation production systems. Under upland conditions, which generally use different cultivars than those grown in wetland conditions, rice attains greater rooting depth than in submerged soils. Sulfur nutrition of rice under upland conditions has much in common with that of other field crops. In submerged soil, access to sulfur is limited by the shallow root system, with >90% of roots confined to the top 20 cm of the soil. Low redox potential causes reduction of sulfate to sulfides, some of which are toxic (H2S), and others low in solubility (FeS, ZnS). Moreover, the slower mineralization of organically bound sulfur decreases availability of sulfur to rice in submerged soils. Hence, sulfur deficiency has increased in prevalence in wetland rice. Negative sulfur budgets have been estimated in several countries where rice is grown without sulfur fertilizers, especially when residue is removed or burned. Further research is needed to develop optimal sulfur nutrient management for the emerging water-saving production systems where soil redox potential fluctuates over time, affecting the mineralization of organically bound sulfur and changing the stability of reduced or oxidized forms of sulfur.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2008. American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, 5585 Guilford Road, Madison, WI 53711-5801, USA. Sulfur: A Missing Link between Soils, Crops, and Nutrition. Agronomy Monograph 50.