Elsevier

Field Crops Research

Volume 270, 1 August 2021, 108192
Field Crops Research

Managing sodic soils for better productivity and farmers’ income by integrating use of salt tolerant rice varieties and matching agronomic practices

https://doi.org/10.1016/j.fcr.2021.108192Get rights and content

Highlights

  • Participatory research ensured better technology packaging, validation and adoption.

  • Gypsum and pressmud–mediated land reclamation better alleviates sodicity stress.

  • Denser planting and additional N improved crop resilience and yield in sodic areas.

  • Improved genetic tolerance and agronomic management bridged yield gaps and enhanced farmers’ income.

Abstract

Regaining the agricultural potential of salt–affected lands offers an opportunity of production enhancement and sustaining food security in less favourable environments. This study aims at deciphering the synergy of adaptive and mitigation strategies– using salt tolerant rice varieties with affordable land reclamation and crop management options. The study was conducted following farmers’ participatory approach for 3 years (2017–19) in sodicity–affected Ghaghar Basin of Haryana, India. Compared with the locally adapted variety PB1121, using the salt tolerant Basmati CSR30 resulted in less yield reduction and better returns, providing better opportunities for stabilizing crop production, and enhancing resilience and adaptation in sodic soils irrigated with alkali water. Gypsum and pressmud–mediated land reclamation reduced soil sodicity, improved salt tolerance and increased yield by ∼35 % compared to the control (2.19 t ha–1). Transplanting two seedlings per hill at 20 × 15 cm spacing resulted in better crop establishment and plant stand, with consequent increase in yield and economic gains over the farmers’ practice of randomly transplanting one seedling hill–1. The significant increase in yields with addition of ∼25 % more N confirmed the farmers’ perception of using more N in sodic soils, suggesting the need for revising existing recommendations. Curve Expert model revealed genotypic variation in N requirements, with 90 kg N ha–1 for CSR30 and 140 kg N ha–1 for PB1121 as economically optimum in sodic soils. Transformative improvements involving the use of adapted stress–tolerant varieties with location–specific agronomic practices increased yield by 6% over the existing recommendations and by 24 % over farmer’s practices; showing potential for bridging the rice yield gaps, halting salt–induced land degradation and improving rural livelihood in salt–affected areas.

Introduction

Soil salinity–induced land degradation caused by natural and anthropogenic factors, and depletion of fresh water in arid and semi–arid regions remains a major obstacle for realizing sustainable crop production worldwide (Murtaza et al., 2017; Moghimi et al., 2018; Minhas et al., 2019). Presence of excess salts (soluble or exchangeable Na+) in the soil affects all aspects of crop growth and development, including germination, vegetative growth and reproduction. The negative effects of salinity stress are associated with osmotic and ion–specific effects, abnormal pH and nutritional imbalances or a combination of these factors (Almeida et al., 2017; Singh and Sharma, 2018; Evelin et al., 2019). Nearly 1125 million hectare (M ha) of agricultural landscape transcending the continental boundaries is salt affected; of which North and Central Asia, including India accounts for ∼20 % of affected area (Hossain, 2019). In India, about 6.74 M ha (∼4.2 % of total arable lands) area is affected by salinity, sodicity or their combination (Tripathi, 2011). If current trends continue unabated, simple extrapolation suggests expansion of salt–induced land degradation to 16.2 M ha by 2050 (CSSRI Vision 2050, https://www.cssri.org). This problem would be more critical in the Indo–Gangetic region where almost 2.7 M ha of salt affected lands are underlain with poor quality water.

Rice is considered an especially salt–susceptible cereal and the crop response to sodicity stress varies with growth stage (Zeng and Shannon, 2000; Upadhyay et al., 2020). Accumulation of elevated levels of sodium (especially Na2CO3 and NaHCO3) in sodic soils during early seedling stage causes high plant mortality; thereby poor crop establishment and low tillering resulting in significant yield losses (Chunthaburee et al., 2016; Kamran et al., 2020). Extensive field trials also showed yield losses ranging from 36 to 69% in rice cultivated on salt–affected soils in comparison to normal ones (Qadir et al., 2014).

Sustainable management of agricultural ecosystems in stress–prone areas requires climate–smart production systems with effective and affordable management practices. Most farmers apply mined gypsum (CaSO4.2H2O) for soil reclamation to remediate alkali water induced soil sodification. Gypsum provides structural stability (better soil aeration and water movement) by displacing the dispersive Na+ ions with flocculating divalent Ca2+ ions from the exchange sites (DeSutter et al., 2014; Schultz et al., 2017). In recent years, the dwindling availability and declining quality of agricultural grade gypsum has impeded sodic land reclamation projects in many parts of the world, fuelling interest in alternative amendments. Effectiveness of pressmud, an environmentally benign amendment, seems to be an affordable solution to lessening pressure on limited gypsum reserves with appreciable reductions in sodicity related problems and concomitant improvements in yield–related traits (Dotaniya et al., 2016; Sheoran et al., 2020). Pressmud is a soft, spongy and amorphous organic material; helps in dissolution of soil native CaCO3, hasten Na+ displacement, and enhances crop nutrient (Ca2+, Mg2+ and K+) availability with appreciable reductions in soil sodicity. Our previous work also emphasized complementary effects of applying gypsum and pressmud together in reducing the soluble salt load, incipient neutralization of alkalinity, and improving environmental adaptability in rice–wheat rotation under sodic conditions (Sheoran et al., 2021a).

Genetic variation in response to sodicity stress exists within and among crop plants, and adoption of tolerant varieties may offer opportunities to reduce risks of crop loss, and raise productivity by avoiding or resisting the stress conditions and through better plant adaptation (Abbas et al., 2013; Sheoran et al., 2021a, b). This will reduce the dependence on costly amelioration practices, and also benefit the resource–limited farmers inhabiting these areas (Singh et al., 2016).

Farmers’ traditional sodicity management strategies often lead to sub–optimal plant stand; implicating significant yield reductions in salt affected soils (Zeng et al., 2002). Crop management options such as optimum seedling density, plant population and balanced nutrient supply were reported to help mitigate the adverse effects of abiotic stresses following rice transplantation (Moradi and Ismail, 2007; Alam et al., 2013; Gautam et al., 2015; Sarangi et al., 2015). Properly spaced crop efficiently utilize more solar radiation for photosynthesis and absorb more nutrients, ultimately contributing to higher yield (Miah et al., 1990; Singh et al., 2016). Sodic soils generally require additional fertilizers such as nitrogen (N) because of their inherently low N content, dispersed and dissolved organic matter (Marchuk et al., 2013), higher volatilization losses (Cameron et al., 2013), restricted microbial activity and N mineralization (Singh, 2015). Research carried out in India and abroad suggests that crops yield more in sodic soils when supplied with higher N than the amount recommended for non–sodic soils; mainly due to dilution effect and improved salt tolerance (Gupta and Abrol, 1990; Murtaza, 2011; Woyema et al., 2012). It is therefore, critical to determine optimum rates of N for crops grown in salt–affected soils that lead to higher yields and resource–use efficiency.

General recommendations for rice production in normal soils are well established (Rice Knowledge Bank; http://www.knowledgebank.irri.org). However, the effectiveness of integrated soil and crop management practices has not been sufficiently validated under alkaline/sodic (irrigated with high residual sodium carbonate water, RSCiw) soil conditions. To improve current understanding and sustain rice production, it is imperative to re–examine the existing recommendations and develop a set of appropriate management practices to offset yield losses in salt–affected areas. This study aims to (a) understand gypsum and pressmud–mediated improvements in yield and associated morpho–physiological responses, (b) assess the performance of two basmati rice varieties; Basmati CSR 30 (hereinafter designated as CSR30), the first sodicity tolerant basmati rice variety, and Pusa Basmati 1121 (hereinafter designated as PB1121), a high yielding rice basmati variety, over a broad range of soil sodicity and to estimate their threshold sodicity tolerance, and (c) establish proper soil reclamation amendments, crop management practices (number of seedlings hill–1and hill spacing) and optimum amount of N requirement. We hypothesize that integrating the matching (soil, crop and nutrient) agronomic practices with salt (sodicity) tolerant varieties will improve productivity, enhance resource–use efficiency and ensure better economic returns in salt–affected areas. The combination of best management options could then be extrapolated to other areas facing similar challenges.

Section snippets

The study sites

Farmers’ participatory field trials were carried out in selected villages (Mundri, Geong, Kathwar, Sampli Kheri and Bhaini Majra) typically representing sodicity–affected soils of the Ghaghar basin (29.762°–29.838 °N and 76.426°–76.518 °E) of Kaithal district in Haryana, India. The study was conducted during the wet seasons of 2017, 2018 and 2019. Climate is subtropical semi–arid with average annual monsoon rain of 760 mm, most of it received during June–September. The mean minimum temperature

Managing soil sodicity through amendments (FPT–I)

Soil sodicity invariably increased in the plough layer (0–15 cm) when no amendment was used for reclamation; increasing soil pH by 0.19 units and ESP by 6% in comparison to the initial values (soil pH: 8.94 and ESP: 31.7 %; Table 2). In contrast, gypsum applied alone (GR50) and in combination with pressmud (GR25PM5) reduced soil pH by 0.38 and 0.24 units, and ESP by 27 and 21 %, respectively. Application of GR50 and GR25PM5, respectively, improved leaf relative water content (RWC; 4% and 6%),

Discussion

This study is an attempt to develop a set of affordable agronomic and soil management practices to boost rice production and profitability in high RSC water irrigated sodic soils.

Conclusions

This study highlights the impact of adaptive and mitigation strategies for management of sodic soils, involving combinations of genetic tolerance and affordable soil, crop and nutrient management options to bridge the gap in rice yield and to enhance farmers’ income. Compared to traditionally grown PB1121, CSR30 showed better salt tolerance and less yield reduction under sodicity stress (soil pH ≥9.2), with reasonably higher profit margins even under lower soil pH (≥8.2). The study also

Declaration of Competing Interest

The author(s) have no competing interests.

Acknowledgements

We sincerely acknowledge the financial support of the Indian Council of Agricultural Research (ICAR), New Delhi, India through Farmer FIRST Project (NRMACSSRISOL201602600924). The authors are also thankful to the farmers their coordination and support while carrying the participatory research.

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      Citation Excerpt :

      Substantial neutralization of soluble HCO3− in irrigation water, displacement of Na+ ions from the exchange complex, and mobilization of Ca+ ions from native CaCO3 in response to GR25 + PM5 mediated amelioration improved soil conditions (flocculation, aggregate stability, nutrient and water uptake) and acclaimed better bio-energetic activities by growing plants under sodic conditions (Choudhary et al., 2011; Minhas et al., 2019). These transformational changes accompanied by better translocation and saturation of essential Ca2+ and K+ ions in plant tissues, improved soil aeration and water movement, and enhanced microbial and enzymatic activities leading to increased morpho-physiological adaptability, biomass accumulation, and ultimately the wheat yields (Oster and Jayawardane, 1998; Shaw et al., 1998; Saviozzi et al., 2011; Sheoran et al., 2021b). Synchronized crop demand and balanced nutrition under SMPs contributed more towards regulating the photosynthetic activity, accumulating osmolytes, scavenging ROS–induced damage and maintenance of N metabolism; thereby, correcting the nutritional imbalances and alleviating the negative effects of salt stress (Shao et al., 2020; Sikder et al., 2020; Wang et al., 2012).

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