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Fluid Journal : Fluid Journal 1999-2001
1 Fluid Journal Spring 1999 Summary: In a dry climate typical ofWest Texas, whereforage production represents a significant part ofa crop's value, deep banding ofPfertilizer can give substantial forage yield advantages. In years with wet fall weather the advantage ofdeep banding P is lost. Grain yield responses are not so closely associated with P placement. Under very dry conditions, significant grain and forage responses to deep placed P hare been observed. But in most production years, over multiple sites, little advantage in grain yield is associated with deep banding P. Drs. Travis D. Miller and Brent Bean Table 1. Wheat forage response to deep-banded P vs. surface- incorporated P in low rainfall plots, Miller, et al., Texas A&M. Placement Runnels Baylor Wichita '87 - '88 '93 - '94 '94 - '95 ------------ lbs/A ------------ Deep-banded 2,583 2,552 2,357 Surface incorporated 1,595 1,248 1,238 Most of the wheat crop in western parts of Texas is grazed by lightweight stocker cattle. Amount and intensity of the crop used for forage varies with price of wheat grain and that of feeder cattle. However, estimates project that more than 70 percent of the Texas wheat crop is grazed in any given year. Grazing duration increases with increasing cattle prices, and with diminishing crop conditions. In most years, 40 percent of the Texas wheat crop is grazed out, with no grain harvested. This extrapolates into about 4.5 million acres of wheat grazed in a given year, with at least 2.4 million acres entirely used as forage. In marginal crop production years, many producers generate more income from grazing than from grain production. Current P fertilizer recommendations and placement technology are derived from grain trials, with no reference to forage production. Grain yield response to P fertility in low to medium P-content soils is widely documented, particularly in higher yield environments. In west Texas, P use has been somewhat poorly accepted by wheat farmers due to sporadic grain yield responses associated with prolonged periods of dry weather in the fall, which limits root development and activity in P enriched zones associated with conventional P placement technology. Several site years of P placement studies in west and west- central Texas suggest that deep banding P results in greatly superior forage yields in winter wheat when drought limits root activity near the soil P Boosts Wheat Forage Yields In West Texas Researchers use irrigated vs. dryland conditions, as well as surface-applied P vs. deep-banded P in multi-site comparison trials. Table 2. Wheat forage response to deep-banded P vs. surface-incorporated P in high rainfall plots, Miller, et al., Texas A&M. Placement Baylor Abilene '94-'95 '94-'95 - - - -lbs/A- - -- Deep-banded 4,295 3,898 Surface incorporated 3,757 4,770 Table 3. Wheat grain response to low rainfall plots (Wichita) vs. high rainfall plots (Abilene) Miller, et al., Texas A&M. Placement Wichita Abilene '94-'95 '94-'95 - - - -lbs/A- - -- Deep-banded 16.4 34.0 Surface incorporated 5.1 48.5 surface. The superior forage response documented in these studies to deep banded P does not universally equate to a proportionally greater grain yield response when compared to conventional P incorporation. Dryland wheat forage Relative to the response of wheat forage to P placement in dryland trials we ran, weather during the early growing season was of great importance.
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