Recipient Organization
LOUISIANA STATE UNIVERSITY
202 HIMES HALL
BATON ROUGE,LA 70803-0100
Performing Department
Dean Lee Research Station
Non Technical Summary
Proper furrow irrigation management requires accurate scheduling. This is accomplished, in part, by knowing when to irrigate and how much irrigation water to apply. Irrigation scheduling usingbest management practices (BMP's)can lead to significant water savings without compromising corn grain yield. Furrow irrigation is the most dominant method used to water row crops in Louisiana.The best irrigation scheduling techniques increase profitability and reduceannual variability in net returns by managing the economic risks associated with irrigation.Corn yields ranging from 175-225 bushels per acre typically respond to 20 - 30 inches of water from irrigation and rainfall. This volume results in about 450-500 pounds of grain per acre-inch of water.Determining the need and timing of a last irrigation to corn is important for optimizing yield and economic return from irrigation. Goals for the last seasonal irrigation to corn are to supply enough root-zone water to maximize yield and allow for depletion of soil water so that off-season precipitation storage is maximized. An additional irrigation applied after the optimal termination timing results in wasted water and energy. Conversely, terminating irrigation too soon on some soils prior to R5 or the dent stage can result in a 15 to 20% loss of grain yield due to insufficient water needed to maximize the weight of individual kernels.
Animal Health Component
100%
Research Effort Categories
Basic
0%
Applied
100%
Developmental
0%
Goals / Objectives
1. Evaluate different irrigation scheduling methods and identify those best suited for Louisiana growing conditions.2. Determine the proper growth stage when irrigation should be terminated for the different soil types in major Louisiana corn production regions.
Project Methods
Currently, recommendations for irrigation scheduling are made subjectively instead of onobjective-based information. To address this issue, a furrow irrigation study will be conducted on an alluvial soil at the Red River Research Station near Bossier City, LA. A corn hybrid that is adapted to Louisiana growing conditions will be selected. Six irrigation timing methods will be replicated three times in a randomized complete block design. Plot sizes will be eight rows on 40-inch row centers by 50 feet in length. Only the middle four rows of each plot will be irrigated to avoid adjoining plots form being compromised. In addition to the six irrigations timing treatments, a dryland or non-irrigated treatment will be included. The six irrigation timing methods will include: (1) watermark sensors at 80 kPa (2) tensiometers at 80 kPa (3) ETc = ETo x Kc (4) 50% ETc replacement, (5) 75% ETc replacement, and (6) 100% ETc replacement. A soil map developed by USDA-NRCS will be utilized to determine the soil series and type.Estimation of evaporation for specific crops ETc is important for irrigation scheduling and agricultural water management. ETc for crops such as corn can be estimated using the following equation: ETc = ETo x Kc where ETo is the evaporation (ET) of a reference crop (cool season grass), which is commonly called reference ET. Both ETc and ETo can be expressed in units such as inches per day. ETo will be measured using an atmometer which is designed to simulate ET from a plant canopy in a way that agrees closely with a plant's resistence to ET. Kc is an adjustment factor referred to as the crop coefficient, which depends on the growth stage of the corn plant. Crop coefficients developed by the University of Arkansas - Division of Arkansas will be utilized in this study.Daily rainfall amounts, ETo and temperatures will be recorded throughout the growing season on a weekly basis. The watermark sensors consist of a modified gypsum block and respond to water conditions by measuring electrical resistance. These sensors are placed in the soil profile at the 6, 18, and 24-inch depths. These sensors are slow to respond to changes in soil water content from irrigation or rainfall event, accuracy is lacking in sandy soils, and requires intensive labor to collect data regularly. Tensiometers measure the tension of the soil water or soil suction and consist of a sealed water-filled tube equipped with a vacuum gauge on the upper end and a porous ceramic cup on the lower end. They work best in sandy soils and only operate to 80 kPa soil moisture. The Calsense ETG® atmometer estimates the amount of ETo and consist of a canvas covered ceramic evaporation plate mounted on a water reservoir. They have a canvas cover that mimic the absorption of solar radiation characteristics of a plant leaf which controls the rate of evaporation. The atmometer is mounted on a wooden post, approximately 40 inches above the ground and is usually located at the edge of the irrigated corn field. Along with the atmometer, crop coefficients will be used to calculate when to schedule irrigation.Deficit irrigation is a strategy which allows a crop to sustain some degrees of water deficit to reduce irrigation costs and potentially increase revenues. Deficit irrigation or evapotranspiration (ETc) based irrigation scheduling is based on replacing ETc losses. In this sudy, 50%, 75%, and 100% ETc replacement will be evaluated with the 100% ETc replacement serving as the reference treatment.Irrigation dates and inches of water applied will be recorded. Phenological data will be recorded each week. At harvest, grain yield, test weight, percent moisture, kernel number, and kernel weight will be evaluated. Also, water use efficiencies of each irrigation treatments will be compared. Crop water use efficiency is defined as yield per unit area divided by water used to produce that yield per unit area. This will enable comparisons between the amount of water lost to deep percolation and the amount of potential chemical leaching into the groundwater during the season. Data will be subjected to statistical analysis using ANOVA and treatment means separated using Fisher's Protected LSD at P < 0.05. Experimental design will be a randomized complete block with three replicates.The cost of irrigating corn should be considered when planning for irrigated production. Optimizing scheduling can reduce irrigation costs and/or increase crop yield or quality. A partial budget analysis will be conducted to determine which technology to recommend. Partial budget analysis is used to analyze many practical farm management practices, such as substituting or changing input levels or types of inputs. A partial budget analysis shows the level of profitability and helps producers to decide whether to adopt a new technology or not by comparing only the positive and negative effects, relevant costs, and incomes in the analysis.Each year at the end of the season, corn producers always ask the question if they should irrigate one last time. To address this need, furrow irrigation termination studies will be conducted at the Red River, Macon Ridge, and Northeast Research Stations. These locations have three distinctly different soil types and are located in major corn growing areas of the state. Soil types for the irrigation sites at the Red River, Macon Ridge, and Northeast locations will be determined by utilizing a soil map from USDA-NRCS. At each location, irrigation will be terminated for the season at beginning dent, dent, ¼ milk-line, or at ½ milk-line stage to determine the optimum time to terminate irrigation for each soil type. These four different growth stages range from approximately 24-10 days prior to black layer or physiological maturity. Experimental design will consist of a randomized complete block and three replications. The need to determine the effects of these time-based delays of irrigation on corn yields have not been quantified for soils in Louisiana. Watermark® soil moisture sensors will be placed in the effective rooting zone of the field (6, 18, and 24 inch depth) to monitor soil moisture status throughout the season. Irrigation will be initiated when sensors read 80 kPa. Rainfall amounts will be recorded throughout the season. At harvest, grain yield, test weight, percent grain moisture, kernel number, and kernel weight will be recorded. Data will be subjected to statistical analysis using ANOVA and treatment means separated using Fisher's Protected LSD at P < 0.05. Experimental design will be a randomized complete block and three replicates.Improved scheduling of irrigation termination for the season can reduce irrigation costs and/or increase crop quantity or quality. A partial budget analysis will be conducted to aid in which method to recommend to farmers. Partial budget analysis is used to analyze many practical farm management problems, such as substituting or changing input levels or types of inputs. A partial budget analysis shows the level of profitability and helps to decide whether to adopt a new technology or not by comparing only the positive and negative effects relevant costs and incomes in the analysis.