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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
Effect of Phosphorus Fertilizer Rate and Application Time on Rice Growth and Yield, 2002
Three studies were conducted (one in 2001 and two in 2002) to examine drill-seeded rice growth, nutrition, and yield response to phosphorus (P) application rate and time. The three sites represent high pH silt loam soils (> 7.5) with a range (8 to 41 parts per million) of Mehlich 3 extractable P (PTBS-2001 = low, Cross-2002 = medium, and Cross–2002 = high). Significant yield responses were observed only in the 2001 study. However, tissue P concentrations have tended to increase as the time of P fertilizer application during vegetative growth was delayed at two of the three sites. This provides solid evidence that P application time is critical for efficient plant uptake of applied P fertilizer. The data clearly demonstrate that a rather complex (i.e., multiple soil chemical properties) recommendation will be needed to accurately predict where P fertilization is required to optimize plant growth and yield since responses do not follow a logical trend of the Mehlich 3 extractable P and soil pH of these study sites.
The most consistent plant growth variable that may show promise to correlate and eventually calibrate rice response to P fertilization is tissue P concentration during early-vegetative growth. When plant tissue P concentration is low (less than 0.20% P) a positive growth and yield response is more likely to occur than when tissue P concentrations are high. The critical P concentration may actually be lower than 0.20% P (less than 0.15 %). The information from these studies will be most useful when rice response to P fertilization can more accurately be predicted since efficient plant uptake will be critical under these situations. These data will also serve as valuable points in the correlation process. Until soil chemical properties are accurately correlated with tissue P concentrations, growers should continue to apply P based on current soil test recommendations at the time which best suits their crop management system. AR-22F
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