Abstract
A pot study was conducted to develop reasonable irrigation scheduling methods for rice-wheat crop rotation by conjunctive use of low-quality brackish water and good quality canal water. Treatments tested were; T1 (canal water), T2 (brackish water), T3 (brackish water for rice and canal water for wheat), T4 (last two irrigations to rice, and initial two irrigations to wheat with canal water), T5 (last two irrigations to rice but two initial and one last irrigation to wheat with canal water). Results revealed that irrigation with canal water resulted in the maximum mean biomass and grain yield of rice and wheat crops followed by cyclic use of brackish and canal water. While continuous irrigation with brackish water resulted the lowest mean biomass and grain yield. The different modes of irrigations also influenced chemical properties of soil, brackish water adversely affected the soil properties, and maximum pH of soil saturated paste (pHs), electrical conductivity of soil extract (ECe) and sodium adsorption ratio (SAR) were recorded where brackish water was used continuously. Therefore, it was concluded that when water is valuable and freshwater resources are limited, cyclic use of the canal and brackish water is also profitable with marginal effect on biomass and grain yield and proves least detrimental for soil health.
Highlights
Due to Pakistan’s arid and semi-arid climate, the agriculture sector of the country is heavily dependent on irrigated farming
A similar trend was observed in the case of grain yield, based on average data of three seasons, maximum grain yield (55.40 g/pot) was documented where canal water was used for irrigation followed by cyclic mode of irrigation which yielded the grain yield of 42.81 g/pot (Table 3)
We designed an irrigation schedule for rice wheat-crop rotation, where both waters were used in seasonal cyclic mode, and canal water was used at the salt-sensitive stage of crop growth, switching over to brackish water at the tolerant stage
Summary
Due to Pakistan’s arid and semi-arid climate, the agriculture sector of the country is heavily dependent on irrigated farming. Drought prevailing conditions and decreased the surface water supply may intensify the practice of irrigation with brackish water that may results in problem of salinity in irrigated lands (Qadir et al, 2007). Sodium adsorption ratio (SAR) represents the soluble Na+ concentration relative to the soluble divalent cation concentrations in the soil solution (Qadir et al, 2008). Water with high sodium content results in dispersion of clay particles and clogging of soil pores (Levy et al, 2003); Na-saturation of clay complex (Minhas et al, 2019); impedes aeration and loss in soil permeability (Choudhary et al, 2011); thereby negatively impacting crop productivity through toxicity of Na+, nutritional imbalances and adverse osmotic effect (Sharma et al, 2016; Murtaza et al, 2017)
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