Scheduling irrigation events in corn using three soil water potential strategies

Authors: Sorensen, Ronald - Ron; Bucior, Erika; Lamb, Marshall

Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Corn is grown on over a half million acres in the tri-state area of Alabama, Florida, and Georgia. Overhead sprinkler systems dominate on large land areas and have been used on small irregular shaped fields for corn production but with high installation costs. Subsurface drip irrigation (SSDI) with drip laterals buried deep enough to allow surface tillage may be considered for these small or irregular shaped areas. However, the expense to install these SSDI systems may prohibit its use in corn due to the low economic returns compared with either cotton or peanut. Another less expensive type of drip system called shallow subsurface drip irrigation (S3DI) can be used to irrigate these small irregular shaped areas. These S3DI systems do not incur high labor or equipment installation costs that are associated with overhead sprinkler or deep buried SSDI systems. Burying drip tubing 1.5 to 2 inches below the soil surface in alternate row middles has been used in corn, cotton, and peanut crops with good success. Scheduling irrigation events for corn has been of great interest for many years to reach a goal of high yield, water water-use efficiency, economics, and water conservation. Currently there are no irrigation scheduling recommendations for S3DI systems for corn production. Previous research has shown that scheduled irrigation events in cotton using soil water potential sensors was feasible. Using this irrigation scheduling technique to schedule irrigation events in corn was tested. The objective of this research was to evaluate three water potential value strategies for irrigation scheduling in corn when using S3DI and the effects on corn yield, test weight, irrigation water use efficiency (IWUE), value water use efficiency (VWUE), and gross revenue. Drip irrigation systems were installed in Dawson, Georgia and Shellman, Georgia. Soil water potential sensors were installed at 10 and 20 inches. Irrigation events were determined when the average water potential was reached. The irrigation triggers were irrigation treatment 1 (I1) between -40 and -60 kPa, irrigation treatment 2 (I2) between -60 to -80 kPa, and irrigation treatment 3 (I3) between -80 to -100 kPa. At each trigger point, 0.8 to 1.0 inch of water was applied through the drip system. Corn was planted across all years and locations. Prior to seeding, 20 lbs N/ac of dry fertilizer was applied along with other recommended fertilizer (P and K) as determined by soil test and incorporated as best possible with strip till unit. A total of 250 lbs N/ac were applied each year using either dry (41-0-0-5.5) or liquid fertilizer (28-0-0-5) depending on nitrogen source, price, and local availability. Nitrogen applications were timed as best possible to coincide with a rainfall just after application to incorporate the fertilizer into the soil. Herbicides, insecticides, and fungicides were applied as recommended by field scouting. Corn was harvested using a commercial corn combine. Seed corn from the combine was transferred into a weigh buggy, weights were recorded, a 0.5 lb subsample was collected for grain moisture and test weight. Irrigation IWUE was determined by subtracting the non-irrigated yield from the irrigated yield and dividing the sum by the total irrigation water applied. VWUE was determined by multiplying IWUE by corn price. Individual year corn prices were used to determine gross revenue and VWUE. The use of soil water potential as a trigger at any of the irrigation treatments described in this research, is a viable option for growers when using S3DI on corn. The use of cellar or radio technology to monitor soil water potential is recommended to provide timely information for decision-making to determine an irrigation event. Water potential trigger points for irrigation scheduling described in this research can conserve water, especially with a heavier soil texture/se

Technical Abstract: Scheduling irrigation events for corn (Zea mays L.) is important for high yield, water use efficiency, economics, and conservation. The use of shallow subsurface drip irrigation (S3DI) is cost effective for small irregular shaped field areas. Currently there are no irrigation scheduling recommendations for S3DI systems for corn production. The objective was to evaluate three water potential value strategies for scheduling irrigation when using S3DI and the effect on corn yield, test weight, irrigation water use efficiency (IWUE), and value water use efficiency (VWUE). Corn was grown multiple years (2012-2013; 2019-2023) at two locations (Dawson,Georgia and Shellman, Georgia, USA) using soil water potential sensors to schedule irrigation events. Sensors were installed at 25 and 50 cm soil depth. Irrigation events were scheduled when the average water potential was between -40 to -60 kPa (I1), -60 to -80 kPa (I2), -80 to -100 kPa (I3), and a dryland control (I0). There was no difference in corn yield, IWUE, or VWUE between irrigation treatments, but all irrigation treatments had greater yield than dryland control, except in years where rainfall was greater than normal. At the Shellman location, total water applied for I3 was 46% less than for I1. At the Dawson location, I2 applied greater amount of water than either I1 or I3. Across both sites, I3 applied less water than the other two treatments. Therefore, irrigation events scheduled at -80 to -100 kPa can be a viable technique for irrigating corn using S3DI without yield reductions and promote water conservation.