Impact of saline irrigation water on sorghum productivity, nutrient uptake, economic returns, and soil properties

Introduction

Salinity is a major environmental stress that severely limits agricultural productivity across the globe. The increasing use of saline groundwater for irrigation has accelerated the expansion of salt-affected soils, particularly in arid and semi-arid regions. Sorghum can tolerate soil and water salinity up to 6.8 and 4.5 dS m -1 of electrical conductivity respectively (Ayers & Westcot, 1985) [2] , beyond these threshold levels yield reductions occur. Irrigation with saline water affects the growth of the plant as it causes osmotic stress, reducing water availability to the plants and nutrient imbalances, reduced nutrient uptake which can lead to a significant reduction in crop yield, reducing productivity (Mrudhula et al. 2025) [13] . There is a necessity to identify various methods for saline water usage in order to reduce salinity impact on crop production. Sorghum cultivated area is 4 million hectares in India with production and productivity of 4.95 million tonnes and 1240 kg ha -1 respectively and Andhra Pradesh has an area, production and productivity of 0.08 million hectares, 0.29 million tonnes and 3459 kg ha -1 respectively (Agricultural Statistics at a Glance, 2024-25) [1] .

Materials and Methods

A field experiment was carried out during the rabi season of 2025-26 at the Agricultural College Farm, Bapatla, Andhra Pradesh, using a split-plot design with three replications. The experiment consisted of three sorghum varieties (NTJ 5, SVT 55 and SVT 68) assigned to the main plots and five irrigation water salinity levels, namely Best Available Water (0.6 dS m⁻¹), 3, 6, 9 and 12 dS m⁻¹, allotted to the sub-plots. The experimental soil was sandy loam in texture, neutral in reaction (pH 7.1) and non-saline (EC 0.7 dS m⁻¹), with low available nitrogen, medium phosphorus and high potassium status. A recommended fertilizer dose of 100:60:40 kg N, P₂O₅, K₂O ha⁻¹ was applied through urea, single superphosphate and muriate of potash, respectively. Saline irrigation water of the desired electrical conductivity levels was prepared by diluting seawater (38 dS m⁻¹) with fresh water (0.6 dS m⁻¹). Salinity treatments were initiated from 20 days after sowing and applied through a drip irrigation system scheduled at 100% pan evaporation at three-day intervals. Attributed yield was recorded at harvest using grain yield. Gross and net returns, benefit-cost ratio were calculated using the cost of cultivation. Nitrogen content (%) in grain and stover was determined using the modified micro-Kjeldahl method as described by Piper et al. (1966) [15] . Plant samples were digested using a diacid mixture of nitric acid and perchloric acid (HNO 3 , HClO 4 ;9:4). Phosphorus content in the digest was estimated by the vanadomolybdophosphoric acid yellow colour method, while potassium content was determined using a flame photometer following the procedure of Jackson et al. (1966) [5] . Nitrogen, phosphorus and potassium uptake were calculated based on nutrient concentration and corresponding grain and stover yields expressed in kg ha⁻¹.

Nutrient content (%) × grain yield (kg ha -1 ) Nutrient uptake in Grain (kg ha -1 ) = 100

Nutrient content (%) × Stover yield (kg ha -1 ) Nutrient uptake in Stover (kg ha -1 ) = 100

Bulk density: Soil bulk density was determined by the core cutter method. Undisturbed soil samples collected using a cylindrical core cutter were oven-dried at 105 °C for 24 h, and bulk density was calculated as the ratio of oven-dry soil mass to the core volume.

=

Where, = Bulk density of soil, mgcm -3 . M = Weight of oven dried soil, mg; and V = Volume of core sampler, cm 3 Saturated hydraulic conductivity, was determined from undisturbed soil cores using the constant head permeameter method (Jalota et al.,1998) [6] . After saturation, conductivity (cm h⁻¹) was calculated as K = QL/∆HAT, where Q is the volume of water collected, L is the soil column length, ∆H is the hydraulic head, A is the crosssectional area and T is the flow time.

Sodium adsorption ratio (SAR):

Soil SAR was determined from the concentrations of Na⁺, Ca²⁺ and Mg²⁺ in the saturated soil extract prepared according to Richards (1954) [16] . Sodium was estimated using a flame photometer, while calcium and magnesium were determined by the EDTA titration method (Jackson, 1973) [5] . SAR was calculated using the standard equation:

SAR =

Exchangeable sodium percentage (ESP): Exchangeable sodium was extracted with ammonium acetate following Black (1973) [3] and estimated using a flame photometer. ESP was calculated as the percentage of exchangeable sodium relative to the cation exchange capacity (CEC).

ESP =

Results and Discussion

Effect of saline water irrigation on grain yield of sorghum varieties Grain yield was significantly affected by sorghum varieties, salinity levels and their interaction. Among the varieties, NTJ 5 recorded the highest grain yield (4822 kg ha⁻¹), while SVT-68 produced the lowest yield (3489 kg ha⁻¹). The higher yield of NTJ-5 may be due to its better genetic potential and grain filling ability, which agrees with Sahar et al. (2024) [17] and Jayalakshmi et al. (2024) [7] . Among the salinity levels, BAW recorded the highest grain yield (4716 kg ha⁻¹), which was on par with 3 and 6 dS m⁻¹, whereas 12 dS m⁻¹ produced the lowest yield (3167 kg ha⁻¹). The reduction in yield at higher salinity was mainly due to salinityinduced stress that reduced water and nutrient uptake, as reported by Mageed et al. (2018) [12] and Govada et al. (2024) [4] . The highest grain yield (5667 kg ha⁻¹) was recorded with NTJ-5 under BAW, while the lowest (2870 kg ha⁻¹) was observed in SVT-68 under 12 dS m⁻¹ salinity, which is in agreement with Kausar and Gull (2019) [9] .

Effect of saline water irrigation on nutrient uptake of sorghum varieties

Nitrogen, phosphorus and potassium uptake in both grain and stover were significantly influenced by sorghum varieties, salinity levels and their interaction. Among the varieties, NTJ 5 recorded the highest uptake of N, P and K, whereas SVT 68 recorded the lowest. The higher nutrient uptake in NTJ-5 may be attributed to its superior yield potential and nutrient use efficiency, which is in agreement with Kumar (2024) [10] and Ju et al. (2021) [8] . Among the salinity treatments, Best Available Water (BAW) recorded the highest nutrient uptake and was statistically on par with 3 and 6 dS m⁻¹, while 12 dS m⁻¹ resulted in the lowest uptake. The reduction in nutrient uptake at higher salinity levels may be due to restricted water and nutrient absorption, impaired root activity and ionic imbalance under salt stress, as reported by Unno et al. (2002) [20] and Vincent et al. (2025) [21] . The interaction effect was significant, with NTJ 5 under BAW recording the highest uptake of N, P and K in both grain and stover, whereas SVT 68 under 12 dS m⁻¹ recorded the lowest uptake.

Effect of saline water irrigation on economics of sorghum varieties

Gross returns, net returns and benefit-cost ratio were significantly influenced by sorghum varieties, salinity levels and their interaction. Among the varieties, NTJ-5 recorded the highest gross returns (₹121,647 ha⁻¹), net returns (₹61,285 ha⁻¹) and B ratio (1.05), while SVT-68 recorded the lowest values.

The superior economic performance of NTJ 5 was mainly attributed to its higher grain yield, corroborating the findings of Sujathamma et al. (2015) [19] and Jayalakshmi et al. (2024) [7] . Among the salinity treatments, Best Available Water (BAW) recorded the highest gross returns (₹118,987 ha⁻¹), net returns (₹58,625 ha⁻¹) and B ratio (0.91), which were statistically on par with 3 and 6 dS m⁻¹. The lowest economic returns were recorded under 12 dS m⁻¹ salinity due to reduced crop productivity, in agreement with Singh et al. (2019) [18] and Kumari (2015) [11] .

The interaction effect was significant, with NTJ-5 irrigated with BAW recording the highest gross returns (₹142,970 ha⁻¹), net returns (₹82,608 ha⁻¹) and B ratio (1.48), whereas SVT-68 under 12 dS m⁻¹ salinity recorded the lowest economic returns and B ratio.

Effect of sorghum varieties and saline water irrigation on soil properties

Post-harvest soil SAR, ESP and bulk density were not significantly affected by sorghum varieties, salinity levels or their interaction. Saturated hydraulic conductivity was not significantly influenced by sorghum varieties or their interaction with salinity levels. However, salinity levels had a significant effect, with the highest hydraulic conductivity recorded under Best Available Water (2.33 cm h⁻¹) and the lowest under 12 dS m⁻¹ salinity (2.00 cm h⁻¹), indicating a decline in soil water conductivity with increasing salinity reported by Mrudhula et al. 2025 [14] .

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