Location: Soil Management Research2012 Annual Report
1a. Objectives (from AD-416):
Objective 1: Evaluate land use systems over agricultural landscapes to determine the effects of management and landscape setting on N dynamics. Sub-objective 1-1. Compare N availability in grasslands and organic pasture to more intensively managed land use systems serving dairy and beef livestock production. Sub-objective 1-2. Compare N availability in organic production to conventional production systems growing alfalfa, corn, soybean, and small grains. Sub-objective 1-3. Develop environmental and economic partial N budgets to compare grasslands, organic and conventional agronomic, and livestock production systems. Objective 2: Develop and evaluate cropping systems for optimal biomass production that maintain or enhance soil productivity. Sub-objective 2-1. Quantify the effect of conventional and alternative biomass production strategies on soil productivity, measured by changes in soil carbon (C) and N, and total biomass and crop yield. Sub-objective 2-2. Develop energy budgets to compare energy use in biomass production systems and evaluate the use of biomass for bioenergy feedstock versus livestock production.
1b. Approach (from AD-416):
An evaluation of N dynamics including an assessment of availability, defined as mineral N forms available for plant uptake, across cropland, grassland and pasture systems will be conducted. We will evaluate alternatives to a strict C-S rotation, including perennial grasses, an annual grass hybrid, a living mulch and a cover crop, to compare the effectiveness of these strategies to mitigate potential negative impacts of harvest and to provide greater biomass and economic returns.
3. Progress Report:
Investigations on land-use impact on soil nitrogen dynamics continued in cooperation with farmers. In situ nitrogen mineralization was assessed in field experiments to compare organic and conventional cropping systems. We continued measuring available nitrogen in a new study with diverse perennial mixtures and evaluated the impact of harvest/residue removal and fertilization of crop and soil variables. We continued a field experiment to develop alternative cropping systems for optimal biomass production including annual and perennial crops in different crop sequences. A database on soil and plant nitrogen dynamics from on-farm sites is finalized and analyses were completed. Due to poor weather conditions and late establishment, data from one of the organic fields was compromised and the experiment was extended to collect new data on soil mineral nitrogen dynamics during summer 2012 in paired conventional/organic systems. Plant biomass and crop yields will continue to be monitored during the current growing season and analyzed for carbon and nitrogen as necessary. We compiled data from on-farm and on-station research for statistical analyses, and performed several simulations at a watershed scale to predict the impact of different management and climate change factors on several ecosystem services.
1. Improved ecosystem services at a watershed scale. Several competing ecosystem services at a watershed level in the upper Midwest will be impacted by climate change. By diversifying the crop rotations and adjusting management practices to fit land capability classes, several ecosystem services, including food production, soil and water conservation, and the production of perennial crops are projected to be balanced under climate change. Results of a simulation study offer strategies for sustainable food and agricultural systems which optimize site-specific crop rotations for improved environmental health through enhanced carbon sequestration and the reduction of soil erosion, runoff, and nutrient leaching.
2. Farmer-managed sugar beets. Sugar beet production in MN, SD and ND constitutes 55% of its total production in the US. A simple sampling and monitoring method of physical development of storage roots and leaves and the dynamics of their sugar contents was developed to investigate reasons behind variation in sugar content at a field-scale. The carbon-to-nitrogen ratio in the developing roots and leaves proved to be a valuable indicator of the dynamics of their sugar content throughout the growing season, and increased in importance towards maturity. The results may have implications for farmers and agronomists to design management practices that can enhance carbon sequestration in the developing roots, maintain adequate level of nitrogen and minimize the variability in root sugar content.
3. Multiple benefits from perennials. Ecological functioning of the intensive, homogeneous agroecosystems in the Chippewa River watershed, MN, USA, can be improved by reducing soil erosion, runoff, and nutrient leaching. These ecosystem services can be achieved through increased perennials in the crop rotations to diversify land use and sustain carbon sequestration. ARS researchers at Morris, Minnesota, calibrated, validated and used Agricultural Production Systems Simulator (APSIM) software to simulate the effect of 100 years each of historical and future climate change scenarios on biophysical processes in representative soil types of the predominant farming systems in the watershed. The interrelationships between crop rotations, soil types, climate variables, and ecosystem services indicated that not all objectives of sustainable agro-ecosystems are compatible, and tradeoffs among them are necessary. Site-specific and diversified crop rotations that comply with the environmental constraints of climate and soil could lead to more efficient implementation of strategies to improve ecosystem services in the watershed if current management practices of high external inputs and tillage persist. We developed guidelines on how to match crop rotations to soil types and land capability classes where perennials can be produced in addition to commodities while improving soil fertility and reducing runoff, soil erosion, and nutrient leaching.Jaradat, A.A., Boody, G. 2012. Modeling agroecosystem services under simulated climate and land-use changes. International Scholarly Research Network (ISRN) Ecology, 2011:Article 568723. Available: http://www.isrn.com/journals/ecology/2011/568723/.