Project Summaries

11-893  Project Manager: E. M. Barnes

METHODS TO DETERMINE CROP WATER STATUS AND IMPROVE IRRIGATION SCHEDULING FOR COTTON

Ruixiu Sui and Daniel K. Fisher, USDA-ARS

There are sufficient ground water resources in the Mid-South with average annual rainfall around 55-inches. The challenge for this region is to manage water resources appropriately, and provide the proper amount of water for crop production during the growing season. Rainfall records reveal that precipitation patterns have changed in the US with an increase in the number of days with heavy precipitation events each year. The change in precipitation patterns has increased runoff on cropland and decreased the amount of rainfall that enters the soil profile. Uncertainty in the amount and timing of precipitation is one of the most serious risks to producers. Typically producers receive higher profits from irrigated crops than from non-irrigated ones. Increasing global competition in cotton requires farmers to reduce input costs and improve crop yield and quality. In recent years, Mississippi cotton producers are becoming increasingly reliant on supplemental irrigation to ensure adequate yields and quality, and reduce risks of production. Improved irrigation scheduling technologies are needed for cotton crops in Mississippi and other humid regions. Therefore, the objectives of this project are to develop improved systems and technologies that automatically monitor cotton crop responses to water to increase irrigation efficiency and profitability, while reducing the adverse environmental consequences of irrigation systems.

In 2012, soil moisture sensing systems were evaluated in a cotton field experiment, and included six Decagon devices with four EM50R loggers and two EM50G loggers with EC-5 sensors. Four low-cost prototypes with Watermark sensors were also installed in a 25-acre cotton field to monitor soil moisture status. Three soil moisture sensors at depths of 6", 12" and 24" were used with one logger at each location in the field. Soil moisture data were automatically collected at one hour intervals. The cotton crop in the experimental field was irrigated based on the soil moisture data collected. During the season, a total water depth of 6.3" was applied in five irrigation events during the season using a center pivot sprinkler irrigation system. Analyzed data and published research results. Data collected in 2011 and 2012 were statistically analyzed for effects of irrigation and nitrogen (N) fertilization on cotton yield and fiber quality.

Results indicated that the soil water sensors were able to measure the soil water status, and the measurements recorded by the systems reflected general trends of soil water change during the growing season. Soil water content decreased at a higher rate in 15-cm and 30-cm depths than in 60-cm depth before 60 days after planting. A sharp decrease of soil water content in 60-cm depth was observed from 60 to 80 days after planting. Sensor measurements responded to effects of soil texture on available water capacity. Canopy temperature of non-irrigated plants is 2-4 C higher than that of the irrigated plants during peak time of day. Irrigation increased cotton yield by 14%. Irrigation improved fiber quality, including length, UQL, fineness, and maturity, UHML, short fiber content, and reflectance in the 2011 season, and UQL and UHML in 2012. Increase of neps in irrigated cotton was observed in 2011, but not in 2012. Effect of leaf N on neps, fineness, and maturity, and the interaction of irrigation with N in these factors, were significant in the 2011 season. Leaf N higher than the critical value (4%) did not improve yield. Excessive application of N occurred as high levels of residual N were not accounted for.

 

Project Year: 2012
 

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