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Interpretive Summaries:
2004 - Effects of Time and Rate of Phosphorus Application on Rice Growth and Phosphorus Uptake
2003 - Rice Response to Phosphorus Fertilizer Application Time and Rate
2002 - Effect of Phosphorus Fertilizer Rate and Application Time on Rice Growth and Yield
2001 - Time and Rate of Phosphorus Fertilizer Application on Rice Growth and Phosphorus Uptake
Rice Response to Phosphorus Fertilizer Application Time and Rate
Five phosphorus (P) studies were conducted in 2004 to evaluate P application time and/or rate effects on the P nutrition and grain yield of rice grown on silt loam soils in Arkansas. Phosphorus fertilizer was broadcast applied before rice emergence or preflood (5-leaf stage) at rates of 0, 25, 50, and 100 lb P2O5/A. Rice grain yield was not significantly affected by P fertilization at any of the sites, possibly because only one of the sites had soil pH >6.9, and it had Mehlich 3-extractable P at 17 mg P/kg of soil. Whole-plant P concentrations at the midtillering stage were generally not affected by P application time, but were influenced by P application rate. The 2004 data indicate that rice is not likely to respond to P fertilization when the pH of undisturbed soils is <7.0.
Rice response to potassium (K, muriate of potash) rate (0, 40, 80, 120, and 160 lb K2O/A applied before flooding) was also evaluated at six sites on silt loam soils in northeast and central Arkansas, with Mehlich 3-extractable soil K ranging from 64 to 132 mg K/kg. Significant grain yield increases with increasing K rate occurred at two sites. Potassium fertilization increased rice grain yields from 183 to 206 bu/A at the Murphy site and from 197 to 213 bu/A at Lake Houge. Grain yields increased numerically as K rate increased to the maximum amount applied. Symptoms associated with K deficiency were present in all K rates to some degree, and the Mehlich 3-extractable soil K did not always predict site responsiveness to K fertilization. Rates of 60 to 90 lb K2O/A are usually adequate to produce maximum rice yields. Other soil extractants are being evaluated to determine if they may be more accurate in predicting rice response to K fertilization. AR-22F
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