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Fluid Journal : Fluid Journal 1993-1995
1 Fluid Journal Fall 1994 by Drs. John L. Kovar and Eddie R. Funderburg Does N -PStar Does N-PStar Does N-P Star Does N-P Star Does N-P Starter Composition Affect ter Composition Affect ter Composition Affect ter Composition Affect ter Composition Affect Phosphate A Phosphate A Phosphate A Phosphate A Phosphate Availa bility in Cotton Soils? vailability in Cotton Soils? vailability in Cotton Soils? vailability in Cotton Soils? vailability in Cotton Soils? Louisiana researchers find that N-P starters increase soil supply of phosphate even in soils that test very high, and that the amount of phosphate in the material, rather than the N:P2O5 ratio, is important. Summary: Applications of N-P liquid starters may significantly increase cotton lint yields at some locations in some years. Likelihood of a response is greater if added material increases the soil supply of N, P, and other nutrients and/or stimulates cotton root growth. Research on ten diverse soils in Louisiana, Mississippi, and Arkansas cotton fields. showed that addition of N- P starter increased both solution and solid phase phosphate, even in soils initially testing very high in available phosphate. Increase in soil phosphate supply varied among soils, but tended to he a function of the total amount of phosphate in the starter rather than the N:P2O5 ratio. However, the N:P2O5 ratio affected the concentrations of K, S, and Zn in soil solution. Since nutrients in soil solution are those most readily available to plant roots, availability of these other elements can he affected by starter applications. Soil phosphate supply data were used in the Barber mechanistic model to predict phosphate uptake by young cotton plants. Results showed that the effect of the starter fertilizer was directly related to the relative increase in solution phosphate concentration after fertilizer application. nterest in starter fertilizer for cotton grown in the mid-South has increased during the last several years. Research in Louisiana, Mississippi, and Alabama has shown that applications of fertilizers I containing nitrogen and phosphorus can significantly increase cotton lint yields. However, yield increases do not occur in every location each year (Figure 1). Due to these inconsistent responses, research continues on liquid starters for cotton grown in Louisiana and surrounding states. In numerous studies, various N:P2O5 ratios (i.e., amounts of each nutrient) were added to different soils. This variation may have influenced root growth and distribution, and subsequent nutrient uptake by the crop. Research with other crop species, such as corn and soybeans, has shown that phosphate and nitrogen are able to stimulate root growth and, therefore, enhance nutrient uptake and grain yield in some soils. A similar response by cotton has been 3,300 3,400 3,500 3,600 3,700 3,800 3,900 4,000 4,100 4,200 Yield of Cotton Seed - lbs/A 1990 1991 Check Starter Tre atm e nt OTT = Surface band, 12 gal/A IFL = in-furrow, 1.5 gal/A IFH = in-furrow, 2.5 gal/A Figure 1. Effect of ammonium polyphosphate (11-37-0) starter application rate and placement on cotton yields, Kovar and Funderburg, Louisiana State University. OTT IFL IFH Table 1. Grades of fluid star ters and their N:P2O5 ratios, Kovar and Funderburg, Louisiana State University. Grade N:P2O5 ratio 0-0-0 unfertilized 15-7.5-0 2:1 15-15-0 1:1 7.5-15-0 1:2 5-15-0 1:3 15-15-5-2S-0.5 Zn complete
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