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Fluid Journal : Fluid Journal 1993-1995
2 Fluid Journal Summer 1994 surface also influences many factors related to fertilizer management. Nitrogen requirements may need to be increased in order to maintain higher productivity under the more intensive cropping systems. At the same time, losses of fertilizer N from the cropping system to the environment, via nitrate leaching and gaseous evolution of ammonia, need to be minimized. The primary focus of this discussion is on the economic viability of more intensive no-till cropping systems in a dryland environment and the N management requirements of a no-till production system where cropping intensity and crop diversity are increased as compared to the traditional wheat-fallow system. Bottom line The take-home message for dryland farmers from research on the intensive cropping system is clearly shown in Table 1. Switching to a wheat-corn- fallow rotation from wheat-fallow dramatically increases the return to land, labor, capital, management, and risk. Without the added crop, corn in this case, producers are the losers even though they switch to no-till in dryland areas. Their mistake is choosing to stick with the traditional wheat-fallow rotation in their attempts to be in compliance with federal conservation regulations. The reason return decreases in a traditional wheat-fallow system with reduced tillage is because herbicide costs increase (i.e., tillage is less expensive than herbicide application) and there is no added crop production to compensate. Just a 50 percent adoption of the more intensive system would increase return to Colorado farmers by $35 million annually. This does not take into consideration monetary trickle down to allied industries or services that may benefit due to increased farmer net profit. For the entire Great Plains, a 50 percent adoption would increase farmer return to land, labor, capital and management by $90 million. Wheat On the average, wheat yields responded to N rate and N source/ placement at both test sites in Sterling (1989-1992) and Stratton (1990-1992), Colorado (Table 2). However, the response of wheat yield to N rate at Stratton was higher than that at Sterling, going from 0 to 90 lbs/A of N. Total soil profile NO3-N data from 1990 and 1991 showed that Sterling had more residual nitrogen (50 to 60 lbs/A of N) than Stratton. The two N source/placement treatments that have annually ranked high in wheat production are UAN split placement and preplant broadcast urea. Averaged over four years (1989-1992), yields were higher at Sterling than the other two treatments; they also rank among the top three treatments at Stratton (Table 2). UAN preplant broadcast generally performed better at Stratton than Sterling. Performance of the UAN split timing treatment generally has been inconsistent and is dependent on weather conditions at sidedress time in the spring. If rainfall occurs after fertilization, N fertilizer will move into the root zone and the method works well. Wheat yields at Stratton responded differently to N fertilizer, depending on the rotation. Lower wheat yields were Table 2. Rotation and N fertilization effects on no-till wheat yields at Sterling (1989-1992) a nd Stratto n , C O (1990-1992). Rotation N Source Placement _________ lb s/A N 1 ___________ 0 30 60 90 _ ____ ____ _ bu/A _ ____ ___ Sterling Wheat-fallow UAN preplant broadcast - 31.2 32.3 35.0 UAN split placement - 32.4 35.0 37.5 UAN split time - 32.7 32.8 34.1 UAN broadcast - 32.7 33.3 35.8 ____ _ 31.2 Mean Wheat corn UAN preplant broadcast - 32.3 31.7 34.1 fallow UAN split placement - 36.5 34.7 37.5 UAN spilt time - 31.0 33.0 32.5 Urea broadcast - 32.7 35.9 38.1 ______ 28.9 Mean Stratton Wheat-fallow UAN preplant broadcast - 40.6 43.8 43.2 UAN split placement - 41.6 44.1 42.7 UAN split time - 38.0 39.3 43.0 Urea broadcast - 40.8 43.6 46.2 ____ _ 37.4 Mean Wheat-corn- UAN preplant broadcast - 36.8 42.3 43.7 UAN split placement - 36.9 38.9 44.7 UAN split time - 35.6 41.4 42.7 Urea broadcast - 40.1 45.0 43.9 ____ _ 30.9 Mean 1N rates at Sterling in 1989 were 0, 25, 50 and 75 lbs/A of N. Split placement = 30% below seed, 70% dribbled over seed. Split time = 30% below seed, 70% sidedressed.
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