2012 Annual Report
1a.Objectives (from AD-416):
1. Develop more efficient management practices for conventional tillage systems with respect to agricultural water use for row crops (cotton, corn, and peanut).
2. Develop improved techniques for irrigation scheduling of surface drip irrigation for row crops and vegetables.
3. Develop management techniques for new and emerging crops in peanut-base rotations irrigated with surface drip.
1b.Approach (from AD-416):
Furrow diked, and non-furrow diked treatments will be applied in a strip-split-plot design with irrigation as main plots and furrow diking as sub-plots with a non-irrigated control. In furrow diked treatments, furrow diking will be conducted after planting, near or before seedling emergence. The basins and dams formed by the 2-paddle furrow diker are commonly 1.5 m long, 0.30 m wide, and 0.2 m deep. The ripper shank will be operated at a depth of about 20 cm in every row middle of furrow diked treatments. Furrow dikes will be created in alternate rows, leaving traffic row middles non-diked. Irrigation timing and amount will be determined using IrrigatorPro. Soil and plant parameters will be monitored using electronic sensors. A rainfall simulator will be used to document soil erosion and infiltration from various treatments and soil series. Meteorological factors will be continuously monitored and recorded using electronic weather stations. Agronomic and economic factors will be recorded for each crop throughout the season and reported as a whole to determine the feasibility of each system. Crop yield, quality, and economic factors will be recorded and compared to express the feasibility of these systems. Agronomic management in field studies will be with current best management practices including transgenic herbicide and insecticide systems. Surface drip irrigation (SDI) will be used to document irrigation strategies for peanut, cotton, corn, vegetable, wheat and canola that will promote economic yield. Crop rotations will have four irrigation treatments and three replications in a randomized complete block design. Individual subplots will be 5.5 m wide by 15 m long. Irrigation events will occur daily, bi-weekly and weekly. Soil moisture sensors will be used to determine the depth of water to apply at each irrigation event. Mini-lysimeters will be installed to document drainage below the root zone. Vegetable crops will be double cropped with peanut and cotton and irrigated with SDI to help increase the economic opportunity to the grower. At harvest time yield and grade of vegetables will be collected to determine economic feasibility. Yield will be determined by weighing a mass of vegetables at harvest time. Individual vegetable grades will be determined using state inspection criteria where grade criteria are available. Winter wheat and canola will be planted with various nitrogen treatments to document best economic yield. Crop water use for all crops will be documented using soil sensors, mini-lysimeters, and crop yield. Crop yield and grade will be determined using normal procedures for cotton, corn, and peanut. Winter wheat will be tested for protein and falling number to determine economic value. Canola will be tested for percent oil extraction (on site bio-diesel extraction) to determine its value as a bio-diesel crop. Water use curves will be determined for each crop using lysimeter and soil sensor data. Crop coefficients will be calculated from estimated actual potential evapotranspiration collected from lysimeter and weather data, respectively.
An existing irrigation system was used with peanut, cotton, and corn to help identify best irrigation techniques. Irrigation events were scheduled at three irrigation trigger points. Irrigation timing and length of time to irrigate were determined using soil moisture sensors to document soil moisture depletion. Water potential and water content sensors were installed at soil depths of 25 and 50 cm in crop rows. Irrigations are scheduled at 60 kPa for all crops. Daily data collected from soil sensors were used to estimate water application depths for each irrigation strategy. Sensors were connected to a datalogger and were interrogated daily to determine irrigation depths using soil moisture depletion.
A research project was initiated where five rates of biochar were applied to the soil surface, tilled into the soil using a field rototiller, and then irrigated with shallow subsurface drip irrigation. The rates include 0, 10, 20, 40, and 60 tons/ac of biochar. The first and second year was planted to cotton. The project was continued this year with corn as the crop planted. The proposed research for this year was to monitor both plant and soil moisture response with different biochar rates.
The impact of Biochar on cotton yield. Biochar has gained importance as a way to increase water holding capacity in soil and to sequester carbon. However, the rates of biochar needed to effect soil characteristics may negatively affect crop yield. This two year study shows the effect of biochar rates of 0, 10, 20, 40, and 60 ton/ac on cotton yield. There was no difference in cotton yield versus biochar rate or across years (2010-2011). The average yield across both years was 3.7 bales/ac. There was no difference in cotton grade with biochar rate or year. These data imply that up to 60 tons of biochar may be added to these soils without adversely affecting yield while sequestering carbon. Soil water holding capacity data has yet to be analyzed.
Long term cotton yield with various irrigation rates. Long term cotton (Gossypium hirsutum L) yield with various irrigation rates and crop rotations irrigated with subsurface drip irrigation (SSDI) is not known for U.S. southeast. A SSDI system was installed in 1998 and maintained for 10 years. The soil was Tifton loamy sand and consisted of three crop rotations, two drip tube lateral spacings, and three irrigation levels. Drip tube laterals were installed underneath each crop row and alternate row middles. Crops were irrigated daily at 100, 75 and 50% of estimated crop water use. There was no lint yield difference due to crop rotation. Lint yield differences were attributed to irrigation treatments in 4 out of 8 years. Lint yields were greatest when irrigated at the 75% irrigation level compared with 50% and in 3 out of 4 years when compared with 100% irrigation treatment. Higher lint yield with irrigation also coincided with lower seasonal rainfall totals. Drip tube lateral spacing affected lint yield 4 out of 8 years. Across all years, yield data indicates that alternate row middle lateral spacing is as effective as every-row lateral spacing. Some fiber qualities were affected by irrigation, lateral, and rotation treatments but these effects were small and inconsistent. For SSDI, the recommendation would be to irrigate cotton using 75% irrigation level and with tubing in alternate row middles.
Sorensen, R.B., Butts, C.L., Nuti, R.C. 2012. Deep subsurface drip irrigation for cotton in the southeast. Journal of Cotton Science. 15:233-242.
Sorensen, R.B., Lamb, M.C., Butts, C.L., Nuti, R.C. 2012. Corn Yield and Economic Return with Nitrogen Applied Through Drip Tubing. Crop Management at www.cropmanagement.org doi:10.1094/CM-2012-0127-01-RS.