Effect of Deficit Irrigation and Irrigation Water Salinity on Soil Chemical Properties in Grain Maize Cultivation under Tape Drip Irrigation System

EXTENDED ABSTRACT

Introduction

The utilization of saline water sources can serve as a solution to address the global water shortage. Drip irrigation is considered a suitable option for utilizing saline water due to its low irrigation water requirement and ability to maintain high soil moisture storage. In the agricultural sector, the investigation of soil chemical properties and effective soil salinity management have long been topics of significant interest to researchers. Hence, the objective of this research is to examine the impacts of deficit irrigation and irrigation water salinity on the chemical properties of soil during the cultivation of seed maize using the single row tape drip irrigation system

Methods

This research was conducted at the experimental station of Agricultural College, Shiraz University, located in the semi-arid Badjgah region (29 ˚32´ N, 52 ˚32´ E and at 1810 m above the mean sea level) of south-western Iran. For this study, a factorial experiment was designed using a randomized complete block design with three replications. The experiment consisted of four levels of irrigation water salinity (0.6, 2, 3.5, and 5 dS m-1) and three levels of deficit irrigation treatments. The irrigation water amount treatments included full irrigation (FI), 75% and 50% of full irrigation. Tape drip irrigation was employed in single rows with a distance of 75 cm between the tapes. To prepare water with different salinities, NaCl and CaCl2 salts were added in equivalent weights to the control water, which had a salinity of 0.6 dS m-1. Soil sampling was conducted at the beginning and end of the growing season, specifically after harvesting. Samples were taken at two depths: 0 to 30 cm and 30 to 60 cm from the soil surface for each treatment, in order to determine soil salinity levels.



Results and Discussion

The findings of this research indicate that as the salinity of irrigation water increases, the concentration of sodium, chloride, calcium, and magnesium ions in the soil, as well as the salinity of the saturated soil extract and the sodium absorption ratio, also increase compared to the control treatment (0.6 dS m-1). The study showed that an increase in water salinity from 2 to 5 dS m-1 resulted in a 57%, 58%, and 61% increase in ECe, a 35.76%, 36%, and 40% increase in soil chloride concentration, a 62%, 60%, and 66% increase in soil sodium concentration, and a 49%, 45%, and 53% increase in the sodium absorption ratio for FI, 75% and 50% of FI, respectively. The main effect of irrigation water salinity revealed that an increase in salinity from 3.5 to 5 dS-1 did not significantly affect soil acidity. Furthermore, the results regarding the relationship between irrigation water salinity and soil chemical properties demonstrate that the use of saline water with deficit irrigation leads to a decrease in the slope of the regression line. The values of soil chloride, potassium, sodium concentration, and the sodium absorption ratio are lower under deficit irrigation when compared to FI. In terms of soil salinity, the application of saline water up to 2 dS m-1 with 75% of full irrigation is deemed suitable. However, under water scarcity conditions, for effective water resource and soil salinity management, it is recommended to use 50% of full irrigation with a salinity of 2 dS m -1 to prevent salt accumulation in the soil.