Nutrient Use Efficiency: An Ecological Approach

The practice of agriculture by humankind intentionally disturbs the nutrient and energy balance (especially Nand C) of natural ecological systems to produce the food, feed, and fiber needed to sustain human activities. These disturbed ecological systems are generally referred to as agroecosystems. A sustainable agroecosystem is one managed for the long-term profitable production of food, feed, or fiber while utilizing the full potential of biological, chemical and physical processes to conserve natural resources and minimize environmental damage (Elliott et al., 1993). Low nutrient-use efficiency is a major factor contributing to the non-sustainability of agroecosystems. To improve efficiency, a more complete understanding of the processes and mechanisms controlling nutrient cycling is needed to develop sustainable agricultural practices. An understanding of nutrient cycling will help refine farming practices to maintain long-term productivity; protect, preserve, and enhance soil resources; and minimize adverse environmental effects, such as sediment, nutrient, and pesticide contamination of our water resources

Improving farm nutrient management by optimizing organic matter inputs and root health

Farmer cooperators conducted strip trials to help investigators create a nutrient and organic matter budgeting system that offered whole farm management guidelines to tighten nitrogen budgets for corn. Corn root health also was analyzed

Soil quality, yield stability and economic attributes of alternative crop rotations

Three long-term rotational crop studies in Iowa and one in Wisconsin were examined for conclusive evidence of rotational effects on soil quality. Long-term yield data also were evaluated to determine if there was a quantifiable relationship between soil quality and yield or yield stability

Integrating Organic Soybean Production on Land Formerly in the Conservation Reserve Program (CRP)

Objectives of this research and education program included an examination of tillage and weed management operations for organic farming on CRP land. In 1999, an experiment was initiated at the ISU McNay Research and Demonstration Farm at Chariton, Iowa, to evaluate the effect of four tillage methods for organic soybean production on land formerly in CRP. After demonstrating the success of organic soybeans on CRP land in 1999 (average yield–49.3 bushels/acre), an expansion of this experiment was initiated in 2000 as a longer term study to examine crop rotations and weed management in organic systems on CRP land

Optimizing the Use of Legume Green Manures in Rotations that Include Corn

Farmers interested in reducing or eliminating the use of synthetic nitrogen (N) fertilizers from their cropping systems often use the N2 fixing capabilities of legume green manure crops in their rotations. The dynamics of N mineralization in the soil after a legume crop are complex and are influenced by many environmental factors. For optimum performance, N-supplying legume crops must decompose sufficiently, and at the appropriate time, to contribute adequate amounts of plant-available N to a subsequent N-consuming crop, such as corn. The objectives of this project were to 1) determine the N fertilizer replacement value of two legumes, alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.), when they were intercropped with oats (Avena sativa L.) and incorporated into the soil in the fall or in the spring preceding a corn (Zea mays L.) crop; and 2) quantify the net N mineralization potential of soil amended with alfalfa and red clover residues during the corn phase of a two-year cropping sequence

Legume Identity and Timing of Incorporation Effects on Soil Responses to Green Manure

Challenges to sustainable agriculture include optimizing nitrogen (N) availability, maintaining profitability by reducing input costs, such as synthetic N fertilizers, and minimizing the loss of nitrate-N. Production of a legume green manure in a crop sequence is a typical method used to reduce or eliminate the need for applying synthetic N fertilizer to succeeding crops. Legumes or legume/small grain mixtures are often used as green manures because of the symbiotic association of most legume species with N fixing Rhizobium bacteria. The dynamics of nitrogen (N) mineralization in the soil after legume incorporation are complex. To contribute adequate amounts of plant-available N to the subsequent crop, the incorporated green manures must decompose sufficiently and in synchrony with the N demand of crops such as corn

Nitrogen conservation in swine manure composting land-application systems

The use of bedding in the popular hooped houses for swine production generates large volumes of manure that composts easily. However, composting results in nutrient losses, especially for nitrogen, which then diminish its value as a fertilizer. This study looks at carbon and nitrogen dynamics in the composting process and subsequent soil mineralization

Comparison of Organic and Conventional Crops, Long-Term Agroecological Research (LTAR) Site

The Neely-Kinyon LTAR site was established in 1998 to study the long-term effects of organic production in Iowa. Treatments at the LTAR site, replicated four times in a randomized complete block design, included the following rotations: conventional Corn-Soybean (C-S), organic Corn-Soybean-Oats/Alfalfa (C-S-O/A), organic Corn-Soybean-Oats/Alfalfa-Alfalfa (CS-O/A-A), and Soybean-Wheat (S-W). Variety selection and planting methods in 2006 were as follows: Pioneer 34A15 corn was planted at a depth of 1.75 in. as untreated seed at a rate of 32,000 seeds/acre in the organic plots and as treated seed in conventional plots, on May 16, 2006. Schillinger 240F.Y soybeans were planted at a depth of 2 in. in organic and conventional plots at a rate of 165,000 seeds/acre on May 22, 2006

Comparison of Organic and Conventional Crops at the Long-Term Agroecological Research Site

The Long-Term Agroecological Research (LTAR)site at the Neely-Kinyon Farm was established in 1998 to study the long-term effects of organic production in Iowa. Treatments at the LTAR site, replicated four times in a completely randomized design, include the following rotations: conventional Corn-Soybean (C-S), organic Corn-Soybean Oats/Alfalfa (C-S-O/A), organic Corn-Soybean Oats/Alfalfa-Alfalfa (C-S-O/A-A), and Soybean-Wheat (S-W). Arapahoe winter wheat was planted October 25, 2006, at 85 lb/acre and Cardinal red clover wasfrost-seeded into the wheat plots on March 15, 2007, at a rate of 12 lb/acre. On April 16, 2007, Kame oats were underseeded with Bluebird alfalfa at a rate of 110 lb/acre and 18 lb/acre, respectively. Following harvest of the organic corn plots in 2006, winter rye was no-till drilled at a rate of 70 lb/acre on November 8, 2006