1a. Objectives (from AD-416):
1. Develop and test tools to build site-specific water and nutrient prescriptions that conserve water, protect the environment, and increase productivity. 1a. Develop water management strategies to optimize spatial water and nutrient applications. 1b. Develop and compare management zones for site-specific irrigation management using NRCS soil maps, detailed soil maps, soil electrical conductivity (EC), and historical yield maps. 1c. Determine the potential role of irrigation in production of alternative crops in the humid Southeast. 2. Develop cropping systems for improving water use efficiency and productivity. 2a. Assess the impact of tillage on soil water status along with plant growth and development. 3. Develop practices and technologies that enhance denitrification with minimized nitrous oxide emissions in water table managed fields and wetlands.
1b. Approach (from AD-416):
This 5-year project utilizes a systems approach to identify and develop strategies for improved water and nutrient management in humid regions. The project includes both irrigated and rainfed productions systems. In irrigation management, (objective 1), the project will focus on developing tools and identifying strategies for a) managing site-specific irrigation systems to conserve water and nutrients, and b) protecting the environment while maintaining cost effective production. In rainfed water management (objective 2), the project will focus on developing and enhancing tillage management systems that improve water use efficiency and increase productivity. In nutrient management, the project will focus on both in-field and off-site management. In-field nutrient management (objective 1) will focus on evaluating nitrogen applications on two soils under a site-specific irrigation system to improve nutrient management and to decrease the potential for off-site nitrogen movement. Off-site nitrogen management (objective 3) will focus on understanding the spatial variability of nitrous oxide emissions from riparian buffers and wetlands.
3. Progress Report:
Irrigation Effect on Flax – A fledgling flax fiber industry has been initiated in the Southeast with the establishment of a processing plant by Naturally Advanced Technologies, Inc., in Pamplico, South Carolina. Under objective 1c and in support of this industry, we conducted our second year of study in 2011-2012 investigating the potential role of irrigation in flax production. Four western European flax fiber cultivars and one oilseed cultivar were evaluated under irrigated and rainfed conditions. Rainfall was plentiful during the spring and irrigation had only a marginal impact on straw yield. It had no influence on seed yield or seed size. The flax fiber cultivars had higher fiber yield than the oilseed cultivar. Long-Term Conservation Tillage – Under objective 2 using plots that have been comparing conventional to conservation tillage since 1978, we initiated a study to determine how tillage affects soil microbial communities (especially arbuscular mycorrhizae on crop roots) and crop productivity. Soil and plant samples have been collected from corn and cotton plots every two weeks from emergence. Root hydraulic conductance, leaf water potential, and leaf gas exchange have been measured on numerous occasions. Sample processing and analysis are in progress. Crop yields are to be determined. Sorghum Irrigation Experiment – the NC Dept. of Agriculture along with a major pork production company are looking at sorghum as a source of local animal feed grain to reduce the amount of imported grains. Under objective 1c, a preliminary experiment was initiated to investigate water and nitrogen management aspects of sorghum production. The experiment consists of 4 water management treatments and 2 nitrogen application rates. Soil moisture and plant biomass will be monitored during the season to assist in developing water management guidelines. Corn Irrigation Experiment – Under objective 1a, a corn irrigation experiment was initiated to evaluate three spatial irrigation scheduling methods. The scheduling methods consisted of: 1) Irrigator Pro; 2) managing soil water potentials <-30 kPa; and 3) irrigation using vegetative reflectance for calculating crop coefficients. Soil water potentials and vegetation measurements have been taken frequently during the growing season. Additionally, soil suction lysimeters have been installed to evaluate the corn nitrogen management and balances. Molecular Analysis of CEAP Wetland Soils – Communities and nitrogen-cycling Genes – Under objective 3, samples from the Coastal Plain region were taken in wetlands converted into agricultural lands; agricultural land restored to wetland status; and natural wetlands. Over 600 samples, with spatial and temporal variability, were collected and DNA extracted. To date, twenty-four samples have been analyzed with next-generation DNA sequencing methods. All samples are being fingerprinted to look at microbial population patterns and how these patterns relate to nitrous oxide emissions. One ARS SY retired in January 2012. Another ARS SY was relocated to Florence from Brooksville, FL. We are evaluating how to modify our project to take advantage of new talents.