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Fluid Journal : Spring 2017
11 The Fluid Journal Spring 2017 The Fluid Journal • Official Journal of the Fluid Fertilizer Foundation • Spring 2017 • Vol. 25, No. 2, Issue #96 David Dunn and Dr. Gene Stevens Summary: Missouri has a long history of rice production, going back to 1910 when the crop was first grown in the northeast region of the state. From this 40-acre start, rice acreage has increased steadily over the years to over 180,000 acres. The statewide average yield was 110 bu/A in 1997 and has increased to over 156 bu/A by 2015. Traditionally, nitrogen (N) management has been given top priority by farmers. But with increased yields and rotations with soybeans, potassium (K) fertility is increasingly being recognized as a yield limitation in some Missouri rice fields. This article covers research conducted at the Missouri Rice Research Farm near Qulin, MO from 1997 through 2016. Introduction Potassium deficiency in rice can reduce grain yields, increase lodging and disease pressure. Visual symptoms of K deficiency in rice first appear in older leaves. These symptoms include a yellowing of leaf tips, increased lodging, decreased disease resistance, and reduced yields. Research conducted at the MU-Fisher Delta Research Center, Portageville, MO, is now highlighting the importance of K in rice production. Initial soil testing and soil fertility research in Missouri focused on improving soil test Potassium on Rice ▼ DOWNLOAD And its effects on yield, grain quality, lodging, and stalk strength. recommendations for K and has now expanded to the diagnosis and correction of K deficiency at mid-season. In the early years of rice production in Missouri the importance of proper K soil fertility was not recognized. This may have been due to low yield potentials and expectations for the rice varieties planted at that time. With the increased rice grain yields resulting from the introduction of modern semi-dwarf and hybrid cultivars, the need for better K management has become clear. The evolution of the University of Missouri soil test recommendations for K in rice production follows this trend. Originally, our recommendations were borrowed from neighboring states with a longer history of rice production. In the early 1990’s the critical level for K in rice production was5XCECinlbsofK2Operacre. The result was very little K being recommended for rice production. As a result of research conducted in the late 1990’s, the critical level was changed to 125 + 5 X CEC in 2003. As this critical level is different from that of the soybean crop often grown in rotation with rice, a good deal of confusion was experienced. We are currently in the process of raising