Location:2011 Annual Report
1a. Objectives (from AD-416)
1) Combine expertise of the USDA-ARS, Agricultural Systems Research Unit (ASRU) in process-based models of cropping systems with cutting-edge dry-land and limited-irrigation experimental research of the Colorado State University (CSU), working in collaboration with the leading ARS limited-irrigation Water Management Research in Fort Collins, the ARS dry-land cropping research at Akron, CO, and irrigation research at the CSU Department of Civil and Environmental Engineering, to create a center of excellence in water limited agro-ecosystems research; 2) use 22 years of experimental data on dry-land cropping systems obtained under prior cooperative CSU-ASRU research and on-going CSU limited-water research to advance understanding of biophysical processes in water-limited cropping of the Great Plains and management practices that promote long-term sustainability of agriculture, water, and the environment; 3) synthesize and quantify that understanding with the help of process models of these systems; and 4) develop quantitative, whole-system based, guidance and decision tools for site-specific optimum crop selections and water-related management for the producers.
1b. Approach (from AD-416)
The CSU-ASRU Cooperative field studies of several dry-land crop rotations on three soil types along a sloping catena of soil types, at each of the three eastern Colorado north-south locations, will be continued for another two years. This will complete the cycles of all dry-land crop rotations being evaluated and provide valuable data on the performance of different crop rotations for 24 years, first 12 years with normal to above normal rainfall and the next 12 years with subnormal rainfall. The detailed measurements of rainfall, runoff, and soil water dynamics (to deduce evaporation and plant uptake) on one location, started two years ago, will be continued and enhanced with measurements of water and N balance in limited-irrigation crop rotation research studies in Fort Collins, CO. At the same time, the existing 22 years of experimental data will be analyzed to relate the year to year production of major crops to variable rainfall and soil water availability at different growth stages, soils, topographic locations, and climates, using statistical and process modeling approaches. The data on soil carbon changes under no-till cropping systems available from the above studies will also be quantified with respect to above conditions. Based on the enhanced understanding derived from above analyses, after first two years, new innovative ways to increase precipitation storage efficiency and water use efficiencies by crops, such as by reducing soil evaporation losses, will be explored under controlled conditions. The knowledge and syntheses derived from above studies will be used to derive simpler tools to guide selection of optimal crops (including bio-energy crops) and conservation/management practices for variable water availabilities for sustainable production and environment.
3. Progress Report
The Revised Universal Soil Loss Equation and the Wind Erosion Equation were used to simulate levels of water and wind erosion under various levels of residue removal in a dryland wheat-corn/sorghum-fallow rotation. DAYCENT model was used to estimate changes in soil organic carbon with residue harvest. Total annual biomass production averaged over site and soil type was 5550 ± 2810 kg ha-1 yr -1 (stover=2750 ± 1570 kg ha-1 yr -1 and grain=2800 ± 1570 kg ha-1 yr -1) for corn and was 5890 ± 2440 kg ha-1 yr-1 (straw=3940 ± 1880 kg ha-1 yr-1 and grain= 1950 ± 820 ha-1 yr-1) for wheat. Wind erosion is a risk under residue removal, with rates surpassing the tolerable erosion levels after removing 10 - 30% of corn stover. However, at all three sites, up to 80% of wheat straw could be harvested without surpassing tolerable wind erosion rates. Soil Organic Carbon (SOC) declined 6-9% after 96 years of simulating 50% removal of corn and wheat stover. Under 0% removal, SOC levels were relatively stable, with maximum declines of 2.0%. Under current Wheat-Corn-Fallow (WCF) management, virtually all wheat and corn stover must remain in order to control wind erosion and maintain soil organic carbon. However, if dedicated non-grain bioenergy crops were grown on an annual basis, there could be 2500-2700 kg ha-1 of harvestable dry biomass available on an annual basis while still retaining enough residues to protect against wind erosion and maintain SOC. This project has identified cropping practices that reduce consumptive water use by 20-50% while maintaining a similar level on-farm income, even without potential income from the saved water. Rotational cropping systems that alternate irrigated crops with fallow or dryland crops were effective at reducing Evapo-transpiration (ET), with average ET reductions of 30-40% compared to continuous corn. Rotating irrigated crops with dryland crops was a much more water efficient approach than rotating with a non-cropped fallow because of high evaporation and drainage during fallow. Annual forage crops such as triticale are good choices for the dryland phase of these rotations because they use residual water and nutrients from irrigated crops and have lower production risk than dryland grain crops. Corn produced after a fallow period or a dryland crop had a higher yield and water use efficiency than continuous corn, illustrating the benefits of crop rotation to maximize water use efficiency. Limited irrigation cropping systems reduced ET by an average of 30%. Both rotational cropping and limited irrigation of sugarbeet and an annual forage crop saved 40% of the reference crop ET. Sugarbeet is drought tolerant and shows good adaptability to limited irrigation. While rotational cropping and limited irrigation systems both reduced ET relative to full irrigation of continuous corn, the rotational cropping systems have an economic advantage over limited irrigation systems because they maximize yields of profitable cash crops in the irrigated phase of the rotation and use lower input crops in the dryland phase. ADODR monitoring is via phone calls, on-site meetings, and personal visits.