Sign up for email alerts of new Fluid Journal issues!
Fluid Journal : Fluid Journal 1993-1995
Dr. J Havlin and L.W. Lohry High R High R High R High R High Residue P esidue P esidue P esidue P esidue Producing Crops and roducing Crops and roducing Crops and roducing Crops and roducing Crops and R RRRReduced- educed- educed- educed- educed-Til l Improve Soil P Til l Improve Soil P Till Improve Soil P Till Improve Soil P Till Improve Soil Productivity roductivity roductivity roductivity roductivity Studies show how practice reduces soil erosion and increases soil organic matterto produce both yield and economic benefits. Winter 1995 Yield (bu/A/in1) Profit Loss ($/A/6 in2) Crop 1 Yield loss in bushels per acre per inch of topsoil loss 2 Profit loss in dollars per acre per 6 inches of soil loss 3 2 1 0 50 45 40 35 30 25 20 Wheat Sorghum Soybeans Figure 1. Influence of topsoil on grain yield and profit, Havlin et al., 1994. Summary: Sustaining or increasing soil productivity and profitability depends on soil and crop management practices that maintain or increase soil organic matter. Crop management systems that include rotations with high-residue producing crops and maintenance of surface residue cover with reduced or no-tillage result in greater soil organic matter, which may improve soil productivity. Increasing input efficiency, protecting the environ- ment, and sustaining the productive capacity of our soils are critical compo- nents of successful farm management. The future and viability of agriculture in the Great Plains depend on sustaining the soil resource base and increasing producer profitability. Conservation technologies provide the greatest opportunity to achieve agricultural sustainability and profitability. It is essential that producers recognize that soil erosion and loss of soil organic matter can reduce soil productivity, which reduces crop yield and profit potential. The practical approach to solving the problem involves a couple of steps: reducing tillage intensity and increasing carbon input through cropping systems that produce more residue. Soil erosion will be minimized and organic matter oxidation reduced. Level of soil organic matter is deter- mined by numerous soil properties that are influenced by cropping practices such as residue management, crop rotation, and many others. Carbon contained in the crop residue is incorporated into the soil as organic matter through degradation of crop residues by soil microorganisms. In one study, for example, tillage in a wheat- fallow system greatly influenced soil organic matter content. Conventional tillage wheat-fallow rapidly reduced soil organic matter, whereas minimum tillage maintained soil organic matter and ultimately enhanced soil productivity. Similarly, organic matter increased when quantity of residue produced increased between soybean/soybean, sorghum/soybean, and sorghum/sorghum rotations in eastern Kansas. However, increase in organic matter was signifi- cantly greater when all residue was left undisturbed on the soil surface (no tillage) compared to conventional tillage. Increasing the quantity of total carbon input by increasing residue and decreas- ing quantity of carbon oxidized or lost by decreasing tillage conserves or increases soil organic matter. Studies also show that the more intensive the crop rotation, the more productive the soil becomes. Our agricultural production system can meet future population demand provided soil and crop management technologies are used to maintain productive capacity of the soil. The challenge is to manage soils so that they will be as productive for future generations as they are today. Understanding those factors that influ- ence soil productivity will help us to identify the appropriate management technologies that sustain or enhance agricultural productivity and profitability. Erosion A significant problem associated with decline in agricultural productivity is the loss of topsoil and soil organic matter. The concerns about declining productiv- ity are not new. Data collected in Kansas wheat fields from 1910 to 1946 show that soil N decreased 50 percent in just 40 years. Approximately 95 percent of soil N occurs as organic N in organic matter. Recent studies in Kansas showed significant loss of soil organic matter associated with erosion of organic matter-rich topsoil. Similar results have been reported throughout the U.S. and Canadian prairie regions and confirmed that soil organic matter decreases about 50 percent during the first 50 years of cultivation. Loss of topsoil by wind and water erosion can reduce the productive capacity of agricultural soils and signifi- cantly reduce profit potential. Erosion- productivity relationships were quantified for dryland winter wheat, grain sorghum,
Fluid Journal 1996-1998