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Fluid Journal : Fluid Journal 1999-2001
1 Fluid Journal Spring 1997 Summary: On low-test P soil, sub-surface banding P increased grain sorghum yield by 20.3 bu/A compared to broadcasting. Placing N and P in a single starter band 2 inches to the side and 2 inches below the seed was as effective as placing a band on each side of the row Knifing N and P in row centers was not as effective as placement beside the row Single- banded starter in N:P2O5 ratios of 1:1 or 3:1 consistently increased yields and nutrient uptake and shortened the time to mid-bloom as compared to the single-banded starter that provided only 10 lbs/A of N. Over the three-year study, 1:1 and 3:1 N:P2O5 starters were clearly superior to other treatments. Use of conservation tillage systems has increased greatly in recent years because of their effectiveness in conserving soil and water. Interest in ridge-till is also growing. This involves planting a crop on a raised bed that is formed by cultivation during the preceding growing season. Ridges 6-8 inches high are built by cultivation when the crop is approximately 15-18 inches tall. Tillage prior to planting is confined to a narrow strip on top of the ridge. Advantages of ridge-till over other conservation tillage methods are: 1) it maintains warmer soil temperatures because of the ridge configuration and removes residue from the seed zone during planting, and 2) it is one of the most economical tillage systems currently used. A major disadvantage of ridge-till is limitation on nutrient placement options owing to a lack of primary Drs. W.B. Gordon and D.A. Whitney What About P Placement and Rate on Furrow Irrigated, Ridge-Tilled Grain Sorghum? Three-year Kansas study shows broadcasting not as effective as banding, plus higher P rates improved yields. Table 1. Growing season weather information. Scandia, KS. Rainfall Avg Daily Temperature 30- 30- 1993 1994 1995 yr avg 1993 1994 1995 yr avg Month-------inches------- - - - - - - -F°------- April 3.38 2.00 1.69 2.52 49.8 51.8 47.8 53.6 May 4.41 1.50 9.41 4.02 61.7 65.5 56.8 64.0 June 6.61 8.50 1.61 4.61 70.7 74.7 69.6 73.9 July 17.79 5.59 3.11 3.82 76.1 73.6 77.7 79.0 Aug 5.59 0.59 4.68 3.71 74.7 74.7 79.5 77.0 Sept 2.91 0.98 2.60 3.90 61.7 67.6 64.8 66.9 Oct 1.69 1.42 0.71 2.01 52.9 55.8 53.8 55.9 Total 42.40 20.59 23.82 24.67 tillage operations. Ridge-till may also alter a crop's rooting pattern and nutrient uptake. Some researchers have shown that broadcasting P is not as effective as sub-surface banding, while others have found no response to P placement in no-till systems. Reports from 1980 research showed an increase in P uptake as volume fraction of soil treated with P decreased, largely because P stimulated root growth in the fertilized portion of soil. Other research has demonstrated that because soils differ in their adsorption capacity of P, the volume fraction of soil to fertilizer for maximum P uptake varies with soil and rate of P applied. Therefore, P application can be over- localized. Stimulation of P uptake by N placed in fertilizer bands has been observed by many researchers. Research in Kansas found that no-till grain sorghum yield on high soil-testing P was improved with starter fertilizer applied in either a 1:1 or 3:1 N:P2O5 ratio compared to the typical 1:3 ratio. Although many studies have examined placement in no-till situations, little information is available about optimum P placement for grain sorghum grown in ridge-till systems. Thus, objective of this experiment was to investigate the effects of P rate and placement method on irrigated grain sorghum grown in a ridge-till system on a low-P available soil. The three-year study was initiated in 1993. Climate Growing conditions were abnormal in 1993. Rainfall in July exceeded the average by nearly 14 inches, but
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