Rice is the staple food and provides livelihood for smallholder farmers in the coastal delta regions of South and Southeast Asia. However, its productivity is often low because of several abiotic stresses including high soil salinity and waterlogging during the wet (monsoon) season and high soil and water salinity during the dry season. Development and dissemination of suitable rice varieties tolerant of these multiple stresses encountered in coastal zones are of prime importance for increasing and stabilizing rice productivity, however adoption of new varieties has been slow in this region. Here we implemented participatory varietal selection (PVS) processes to identify and understand smallholder farmers’ criteria for selection and adoption of new rice varieties in coastal zones. New breeding lines together with released rice varieties were evaluated in on-station and on-farm trials (researcher-managed) during the wet and dry seasons of 2008–2014 in the Indian Sundarbans region. Significant correlations between preferences of male and female farmers in most trials indicated that both groups have similar criteria for selection of rice varieties. However, farmers’ preference criteria were different from researchers’ criteria. Grain yield was important, but not the sole reason for variety selection by farmers. Several other factors also governed preferences and were strikingly different when compared across wet and dry seasons. For the wet season, farmers preferred tall (140–170 cm), long duration (160–170 d), lodging resistant and high yielding rice varieties because these traits are required in lowlands where water stagnates in the field for about four months (July to October). For the dry season, farmers’ preferences were for high yielding, salt tolerant, early maturing (115–130 d) varieties with long slender grains and good quality for better market value. Pest and disease resistance was important in both seasons but did not rank high. When farmers ranked the two most preferred varieties, the ranking order was sometimes variable between locations and years, but when the top four varieties that consistently ranked high were considered, the variability was low. This indicates that at least 3–4 of the best-performing entries should be considered in succeeding multi-location and multi-year trials, thereby increasing the chances that the most stable varieties are selected. These findings will help improve breeding programs by providing information on critical traits. Selected varieties through PVS are also more likely to be adopted by farmers and will ensure higher and more stable productivity in the salt- and flood-affected coastal deltas of South and Southeast Asia.

Soil is a finite natural resource and is indispensable for human civilization because it is the medium for food production for the biosphere. Continued soil degradation is a forerunner of catastrophe for the living world. The protection of healthy soils and the restoration of problem soils are strongly needed in the current agricultural scenario as competition for urbanization and other human needs for land resources limits the scope for the further availability of land for agriculture. Naturally occurring degraded soils, such as acid sulphate soils, can be restored with scientific interventions and advanced management strategies. The Ganges Delta is a densely populated region, where the inhabitants’ major livelihood is agriculture. Soil acidity and salinity restrict crop performance in this coastal region, particularly the acid sulphate soils (ASSs) posing a risk to agriculture. ASSs are developed from land-use changes from mangrove forest to agricultural land in this region. There is no systematic study on these soil types covering Bangladesh and India. This paper unfolds several aspects related to the characteristics, problems, and detailed management strategies of ASSs relevant to the Gangetic Delta region where these soils continue to be used for intensive agriculture to meet the livelihood needs. Crop yields are very poor in the unmanaged ASSs due to a very low soil pH (<3.5), hampering the growth and development of crops due to nutrient deficiencies and/or toxicities, coupled with soil salinity. There is toxicity of water-soluble Fe, Al, and Mn. The phosphorus nutrition of crops in these soils is affected owing to a high soil P fixation capacity. A deficiency of micronutrients, such as Zn and Cu, was also observed; however, K availability is variable in the soil. The soil acidity is a general problem throughout the soil profile; however, extreme acidity (pH < 3.5) in particular soil horizons is a typical soil characteristic, which creates problems for its efficient management. Specific operations, such as the selective use of soil layers with good properties for crop root growth, major and minor nutrient applications, and soil amendments, including green manuring, application of biofertilizers, and soil microbes, are gradually improving the properties of these soils and bringing back the potential for good crop production. Scientific water/drainage management is needed to gain an agronomic advantage. Evidence of increased crop yields in these soils observed from green manuring, lime, basic slag, and rock phosphate application are presented.

Rice-fallow and rice-rice are major cropping systems in the salt affected region of the Ganges Delta covering West Bengal, India and Bangladesh. The dry season rice (Boro) is grown mostly by irrigation from ground water in this water scarce region. Boro encounters soil and water salinity, air temperature fluctuations and intense evaporative demand. We studied six sowing dates (1 October, 15 October, 1 November, 15 November, 1 December and 15 December) and three varieties (WGL 20471, Bidhan 2 and IET 4786) of rice to find an interacting effect on yield and water productivity. Soil and water salinity varied during the growing period with lower soil salinity during the month of November (2.20–2.53 dS m⁻¹) and higher soil salinity towards the end of the growing season (4.30–5.23 dS m⁻¹). The mean field water salinity was higher (1.78 dS m⁻¹) during the Boro 2017–18 compared to that (1.65 dS m⁻¹) during 2016–17, as about 49 mm rainfall was received in the month of March 2017. Sowing dates significantly affected the yield of Boro rice. Earliest sowing on 1 October is not feasible as it significantly reduced the grain and straw yields. Sowing of nursery up to 1 of November was found to be the best possible option, and it should not be delayed up to 15 December. The rice variety IET 4786 was found to be susceptible to salinity with the lowest grain yield 2.65–2.98 t ha⁻¹, compared to Bidhan 2 (3.41–5.95 t ha⁻¹) and WGL 20471 (3.40–5.81 t ha⁻¹). Both irrigation and economic water productivity of Boro were affected by sowing dates and variety. Rice variety IET 4786 required less irrigation water (1320 mm) than the other two varieties (1350 mm). Higher (>0.5 kg m⁻³) irrigation water productivity of Boro can be achieved by selecting salt tolerant varieties (WGL 20471 and Bidhan 2) and optimum sowing window of 1–15 November.

Rice is the predominant crop during wet season (July–December) and majority of land remain fallow during dry season (January–June) in the coastal saline region of West Bengal, India. Sustainable cropping system intensification in this salt affected region needs improved package of practices which conserve soil moisture, facilitate early crop establishment, ensures profitability and has positive effect on soil health. To achieve these objectives in a rice-based cropping system, we evaluated seven treatments for potato crop during the dry season viz. T1: ridge sowing (control), T2: Zero tillage (ZT) sowing with 9 t ha⁻¹ paddy straw mulching (PSM), T3: T2 + foliar spray of nutrients, T4: ZT sowing with 12 t ha⁻¹ PSM, T5: T4 + foliar spray of nutrients, T6: ZT sowing with 15 t ha⁻¹ PSM, T7: T6 + foliar spray of nutrients in randomized block design with five replications. This study was conducted during 2016-2019 in the Gosaba island of the Indian Sundarbans. Cost of cultivation of potato reduced by about 27% due to ZT sowing (₹ 81,287 ha⁻¹) compared to ridge sowing (₹ 1,11,260 ha⁻¹). Tuber yield, net return and irrigation water productivity was significantly increased in T5, T6 and T7 over other treatments. There was reduction in soil salinity (ECe reduced from 5 to 3 dS m⁻¹), bulk density (from 1.49 to 1.44 Mg m⁻³), irrigation water use (less 20 cm), conservation of soil moisture (4–8%), and increase in organic carbon (0.39 to 0.44%) due to ZT sowing with PSM. Rice-ZT potato-green gram cropping system was the most profitable one with highest net return (₹ 1,71,752 ha⁻¹), however, the benefit-cost ratio was highest (2.33) with Rice-ZT potato cropping system.