Restoring soil quality and carbon sequestration potential of waterlogged saline land using subsurface drainage technology to achieve land degradation neutrality in India.

Subsurface drainage (SSD) has been proved to be an effective technology to reclaim waterlogged saline soils. Three SSD projects were implemented in Haryana, India in 2009, 2012 and 2016 to study the long term effect of SSD (10, 7 and 3 years) operation on restoring productivity and carbon sequestration potential of degraded waterlogged saline soils under prevalent rice-wheat cropping system. These studies indicated that successful operation of SSD improved soil quality parameters such as bulk density, BD (from 1.58 to 1.52 Mg m-3), saturated hydraulic conductivity, SHC (from 3.19 to 5.07 cm day-1); electrical conductivity, ECe (from 9.72 to 2.18 dS m-1), soil organic carbon, OC (from 0.22 to 0.34 %), dehydrogenase activity, DHA (from 15.44 to 31.65 µg g-1 24 h-1), and alkaline phosphatase, ALPA (from 16.66 to 40.11 µg P-NP g-1 h-1) in upper soil surface (0-30 cm). The improved soil quality resulted in increased rice-wheat system yield (rice equivalent yield) by 328 %, 465 % and 665 % at Kahni, Siwana Mal and Jagsi sites, respectively. Studies also revealed that carbon sequestration potential of degraded land increased with the implementation of SSD projects. The principal component analysis (PCA) showed that % OC, ECe, ALPA, available N and K content were the most contributing factor for soil quality index (SQI). The overall result of the studies showed that SSD technology holds great potential to improve soil quality, increase crop productivity, farmers' income and ensure land degradation neutrality and food security in waterlogged saline areas of western Indo Gangetic Plain of India. Hence, it can be concluded that large scale adoption of SSD may fulfill the promise "No poverty, Zero hunger, and Life on land" sustainable development goals of United Nation in degraded waterlogged saline areas.

Matching N supply for yield maximization in salt-affected wheat agri-food systems: On-farm participatory assessment and validation.

Driven by the UN-SDGs of achieving food security and agricultural sustainability, it remains more challenging in degraded ecosystems to simultaneously improve the crop performance without creating unintended favour for excessive fertilization and associated environmental consequences. We assessed the N-use pattern of 105 wheat-growers in sodicity affected Ghaghar Basin of Haryana, India, and then experimented upon to optimize and identify indicators of efficient N use in contrasting wheat cultivars for sustainable production. The survey results revealed that majority of farmers (88%) have increased their reliance on N nutrition (∼18 % extra N), and even extended their duration of N scheduling (12-15 days) for better plant adaptation and yield insurance in sodicity stressed wheat; albeit to a greater extent in moderately sodic soils applying 192 kg N ha-1 in 62 days. The participatory trials validated the farmers' perception of using more than the recommended N in sodic lands. This could realize the transformative improvements in plant physiological [higher photosynthetic rate (Pn; 5 %) and transpiration rate (E; 9 %)] and yield [more tillers (ET; 3 %), grains spike-1 (GS; 6 %) and healthier grains (TGW; 3 %)] traits culminating in ∼20 % higher yield at 200 kg N ha-1 (N200). However, further incremental N application had no apparent yield advantage or monetary benefits. At N200, every additional kilogram of N captured by the crop beyond the recommended N improved grain yields by 36.1 kg ha-1 in KRL 210 and 33.7 kg ha-1 in HD 2967. Further, the varietal differences for N requirements, with 173 kg ha-1 in KRL 210 and 188 kg ha-1 in HD 2967, warrants the need of applying balanced fertilizer dose and advocate revision of existing N recommendations to cope up the sodicity induced agricultural vulnerability. Principal Component Analysis (PCA) and correlation matrix showed N uptake efficiency (NUpE) and total N uptake (TNUP) as the highly weighted variables illustrating strong positive association with grain yield, and potentially deciding the fate of proper N utilization in sodicity stressed wheat. Key insights suggested that combining participatory research with farmers' knowledge and local perspective could be decisive in better integration of technologies, and serving to adapt the real-time soil sodicity stress and sustaining wheat yields with economized farm profits.

Integration of organics in nutrient management for rice-wheat system improves nitrogen use efficiency via favorable soil biological and electrochemical responses.

Introduction: The contrasting soil management in flooded-transplanted rice (Oryza sativa) and dry-tilled wheat (Triticum aestivum) poses a challenge for improving low nitrogen use efficiency (NUE) of the rice-wheat system. Integration of organics in nutrient management can bring in changes favoring efficient N uptake via changes in growing conditions and soil responses. Materials and methods: This study reported the results of a 15-year-long experiment on integrated nutrient management (INM) systems for rice-wheat cropping. The INM included substituting ~50% of chemical fertilizers via (i) including a legume crop (Vigna radiata) in the sequence and its biomass incorporation (LE), (ii) green manuring with Sesbania aculeata (GM), (iii) farmyard manure application (FYM), (iv) 1/3 wheat stubble in situ retention (WS), and (v) 1/3 rice stubble in situ retention. Results and Discussion: The INM strategies resulted in improved NUE compared to 100% chemical fertilizers (F). The INM had significantly higher net N mineralization and improved biological activity aligning with the NUE trends. The reductions in redox potential (Eh) and pH during rice season improved NUE under integrated management. Highly reduced conditions favored N mineralization and plant availability in form of NH 4 + - N resulting in enhanced uptake efficiency, in rice crop. The soil organic carbon (C) significantly increased in INM, and an effect of the active C fractions was evident on the NUE of the wheat crop. Conclusion: The results showed that these INM strategies can immensely benefit the rice-wheat system via improvement in biological health along with electrochemical changes for flooded rice, and labile-C-assisted improvement in soil conditions for wheat.

Deficit saline water irrigation under reduced tillage and residue mulch improves soil health in sorghum-wheat cropping system in semi-arid region.

Judicious application of saline water except for critical growth stages, could be the only practical solution to meet the crop water demand in arid and semi-arid regions, due to limited access to freshwater, especially during dry winter months. A field experiment was conducted to study the effect of tillage [conventional (CT), reduced (RT), and zero (ZT)], rice straw mulch and deficit saline-water irrigation in wheat (100, 80 and 60% of wheat water requirement, CWR) followed by rainfed sorghum on soil properties and the yields of the cropping system. Yields of both the crops were comparable between RT and CT, but the wheat yield was reduced in ZT. The RT, mulching and deficit saline irrigation in wheat season (60% CWR) increased the sorghum fodder yield. Olsen's P (8.7-20.6%) and NH4OAc-K (2.5-7.5%) increased in RT and ZT, respectively, over CT under both the crops. Deficit irrigation reduced soil salinity (ECe) by 0.73-1.19 dS m-1 after each crop cycle, while soil microbial biomass C (MBC) and N (MBN), dehydrogenase, urease and alkaline phosphatase reduced with an increase in ECe. The α-glucosidase, MBC, ECe, KMnO4oxidizable N, and urease were identified as major contributors in developing the soil health index. Deficit irrigation (60% CWR) and rice straw mulching under ZT and RT showed higher values of soil health index. Overall, deficit saline-water irrigation under reduced tillage and straw mulching had the greatest potential in maintaining soil health, saving fresh irrigation water without affecting the productivity of the sorghum-wheat system in the semi-arid regions of India. Results also demonstrated that salt affected areas of arid and semiarid countries can replicate the protocol for indexing and screening of soil health indicators to assess the sustainability of a cropping system. This integrated management based on the nature of the available resources also provided a practical approach to achieve the target of land degradation neutrality and land restoration.