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Fluid Journal : Fluid Journal 1993-1995
1 Fluid Journal Fall 1995 Summary: Soil sampling is the beginning point of nutrient management in a reduced-till program. Problems routinely observed in reduced-till are stratification of immobile nutrients and loss of the mobile nutrient N via volatilization, nitrification, etc. Overliming can be a problem in reduced- till. Keys to success in reduced-till are proper placement of nutrients (surface banding or subsurface banding) and timing of application (especially N). Starter fertilizer is a foundation for proper nutrient management in a conservation tillage system. Effects of surface residues must be accounted for and fertilizer contact with residues minimized. reduced-till system consists of at least five components: cropping strategy, pest management, residue management, nutrient management, and tillage. Each part must work in harmony with the different elements of the system. The ideal plan incorporates these essential components to form a cohesive whole. In this article, we'll focus on nutrient and residue management. Where to begin Management in a reduced-till system begins by accounting for all nutrients and matching supply with crop demand. Soil testing, applying legume credits, and taking into consideration nutrient loading from manures and sludges are all necessary to accurately predicting fertilizer needs. Soil testing is usually accomplished by Dr. Raun Lohry Managing R ManagingR Managing R ManagingR Managing Reduced Til lage Systems educed Til lage Systems educed Tillage Systems educed Tillage Systems educed Tillage Systems Nutrient and residue management are key componentsin a cohesive program to maximize crop yields A by one of two methods: grid sampling or by soil type. Grid sampling involves taking samples from small tracts of land and performing computer analyses. Fertilizer applications are based on the nutrient need of each tract. Sampling by soil type involves collecting cores from similar soil types on areas smaller than 25 acres. Fertilizer is then applied to the whole soil type in the sample area. Soil tests and fertilizer recommendations for individual nutrient application rates can be obtained from local fertilizer dealers, testing labs or university cooperative extension services. Regardless of the soil sampling system employed, the soil zone between six and eight inches often is used to estimate availability of non-mobile elements such as phosphorus, potassium, zinc, and other micronutrients. The sampling area for nitrogen can vary by area, so be sure your soil testing lab knows how deep the sample was taken. Some states use a four-foot average and others use two or just the top foot. Manures and sludges should be analyzed for N, P and K before application. Care should be taken to apply as evenly and accurately as possible. Document for future reference where manure applications have been made. Don't overlime P and K soil tests usually check for lime requirements. Because conservation tillage reduces the soil volume that can react with lime, the quantity of lime applied must be adjusted to avoid overliming. As a general rule, conservation tillage systems reduce soil volume that reacts with lime by half. Liming recommendations should be reduced accordingly. Overliming can induce micronutrient deficiencies such as zinc, manganese, and iron. It can also increase carryover potential of some herbicides. Lime often needs to be applied more frequently in reduced-till because the volume of soil that acidifying fertilizers react with is less. Figure 1. Stratification of P and K in different tillage systems. P K PK-lbs/A 300 250 200 150 100 50 0 0-3" Plow 0-3" No-till 3-6" Plow 3-6" No-till 6-9" Plow 6-9" No-till 9-12" Plow 9-12" No-till SOIL DEPTH
Fluid Journal 1996-1998