A detailed study on genetic diversity, antioxidant machinery, and expression profile of drought-responsive genes in rice genotypes exposed to artificial osmotic stress.

Seasonal variations in rainfall patterns, particularly during sowing, early growing season, and flowering, drastically affect rice production in northeastern India. However, sensitivity to drought stress is genotype-specific. Since 80% of the land in this region is used for rice production, it is crucial to understand how they have adapted to water stress. This study evaluated 112 rice genotypes grown in NE India for seed germination percentage and seedling development under PEG-mediated drought stress. Among the rice genotype, Sahbhagi dhan, RCPL-1-82, Bhalum-3 and RCPL-1-128 showed drought-tolerant traits, while Ketaki Joha, Chakhao, Chandan, RCPL-1-185 and IR-64 were the most drought-sensitive rice genotypes. Drought-tolerant rice also showed significantly higher seed germination potential, proline content, antioxidant activity and expression of drought-responsive genes than drought-sensitive rice genotypes. A similar expression pattern of genes was also observed in the rice genotype treated with a 50% water deficit in pot culture. In addition, drought stress reduced the pollen fertility and yield per plant in sensitive rice genotypes. Molecular markers associated with drought stress were also used to characterize genetic diversity among the rice genotypes studied.

Runoff and soil erosion in the integrated farming systems based on micro-watersheds under projected climate change scenarios and adaptation strategies in the eastern Himalayan mountain ecosystem (India).

Land degradation caused by soil erosion (SE) in forests converted into cropland under climate change, particularly with increased rainfall intensity, is of great concern to the agricultural sustainability of the tropical mountain ecosystem. We evaluated the response of six hilly micro-watersheds (HMW) under different Integrated Farming Systems (IFSs) to SE in multi-model climate change scenarios using the Water Erosion Prediction Project (WEPP) model. The IFSs were forestry (HMW1), abandoned shifting cultivation (HMW2), livestock with fodder crops (HMW3), agroforestry (HMW4), agri-horti-silvi-pastoral (HMW5), and horticulture (HMW6) established on a hilly slope (32.0-53.2%) of the eastern Himalayas (Meghalaya, India). The WEPP model was calibrated and validated with measured runoff and soil loss data of 24 years for each of the six IFSs. The projected annual SE (average) for all HMWs increased in all RCPs. The IFS based on shifting cultivation (HMW2) was the most vulnerable, with the highest percentage increase in SE (46-235%) compared to the baseline years (1976-2005) under RCP 8.5. The cultivated IFSs (HMW3 to HMW6) had 47.8-57.0% less runoff and 39.2-74.6% less soil loss than HMW2 under RCP 8.5. Of these, HMW6 followed by HMW4 and HMW5 were the most effective at minimizing soil loss. Simulation results showed a reduction in soil loss through adaptive strategies such as mulching with broom grasses, stones, field beans, and the introduction of subsurface drainage. Adoption of IFS based on horticulture and agroforestry with bio-mulching on steep slopes is an effective measure to control soil erosion in the eastern Himalaya (India).

Converting primary forests to cultivated lands: Long-term effects on the vertical distribution of soil carbon and biological activity in the foothills of Eastern Himalaya.

The conversion of primary forests to cultivation brings a significant change in soil carbon (C) forms. In the foothills of the Eastern Himalayan Region of India (Manipur), such conversions are prevalent. However, little is known about the response of C forms, particularly in deep soil, to land use conversion in the region. We evaluated changes in soil C forms (total organic, inorganic, and pools) and microbiological properties (up to 1.0 m depth) mediated by C when the 45-year-old forest had been cultivated for 18-25 years. The cultivated land uses were tree-based agroforestry (LAF: legumes, NAF: non-legumes), horticultural fruits (WHF: woody, NHF: non-wood, mainly vegetables), and paddy agriculture system (AUS: upland, ALS: lowlands). Forest conversion significantly (p < 0.05) decreased the total carbon (TC) in the surface soil (0.0-0.15 m) from 4.88 % to 3.04-3.93 % in the tree-based land uses (LAF, NAF, and WHF). TC further declined to 2.05-2.81 % under seasonal crops (NHF, AUS, and ALS). Seasonal crop cultivation also caused a higher decline in microbial biomass carbon, soil enzymes, and carbon pools (active and passive) than the tree-based land use with the soil depth. The vertical distribution of C in the soil profile was inconsistent: organic C (including C pools) decreased, while inorganic C increased. The profile TC stock to a depth of 1.0 m in the forest was 358.8 Mg ha-1, of which 81 % were organic C, and 19 % were inorganic C. In comparison with forest soil, total soil C stocks (organic and inorganic) decreased more (-44.1 to -55.1 %) in seasonal crops than in tree-based (-15.4 to -36.3 %) land uses. The degradation index (DI) also confirmed that seasonal crop cultivation caused a larger decline in surface soil quality (DI: -423 % to -623 %) than tree-based land use (DI: -243 % to -317 %). The topsoil (up to 0.45 m) of seasonal crops was more degraded than that of the subsoil (>0.45 m-1.0 m). Forests converted to seasonal cultivation (upland rice and vegetables) caused higher degradation of soil C forms and overall soil health in the Himalayan foothills of northeastern India. We suggest the promotion of Agroforestry based on legumes (Parkia spp.) and woody fruits (mango/citrus/guava) in the uplands to minimize soil C degradation while ensuring nutritional security in the hill agro-ecosystems of the Indian Himalayas.

Effect of land-use change along altitudinal gradients on soil micronutrients in the mountain ecosystem of Indian (Eastern) Himalaya.

Management of soil micronutrients for better crop production needs a sound understanding of their status and causes of variability. This is more relevant for acid soils of the mountain ecosystem of Eastern Himalaya (Northeast India). We assessed the status, and the effect of land uses along altitudinal gradients (14 to 4090 masl) on soil properties and micronutrient concentrations (DTPA extractable Fe, Mn, Cu, and Zn) across the region. Soils varied widely in micronutrient concentrations: Fe from 0.665 to 257.1 mg kg-1 while Mn, Cu, and Zn from traces to 93.4, 17.1, and 34.2 mg kg-1, respectively. On conversion of evergreen forests (EF) to upland agriculture (Shifting-SC and Settled-SA) and plantation (PH), Mn, Cu, and Zn concentrations decreased significantly from 30.5, 1.74, and 2.13 mg kg-1 to 6.44-17.8, 0.68-0.81, and 1.06-1.42 mg kg-1, respectively. Grassland (GL) and lowland paddy (LP) had comparable Fe, Mn, and Cu concentrations (except Zn). Degradation of EF to scrubland (SL) recorded the lowest Mn (5.91 mg kg-1), Cu (0.59 mg kg-1), and Zn (0.68 mg kg-1) concentrations. Fe concentration was however increased in degraded SL (+ 73%) over EF (48.7 mg kg-1). The distribution of micronutrients among the land uses was inconsistent and followed the order: (i) Fe: SL > PH > LP > EF > GL > SC > SA, (ii) Mn: EF > GL > LP > PH > SC > SA > SL; (iii) Cu: EF > GL > LP > SC > SA = PH > SL; and (iv) Zn: GL > EF > LP > SC > SA > PH > SL. Four micronutrients responded differently and followed a non-linear, 6th-order polynomial trend along the altitudinal gradients (< 500 to 4100 masl). Peak concentrations of Fe, Mn, and Cu were recorded at 1001-2000 m while Zn was recorded at > 4000 masl. The variability (54-64%) in soil micronutrients was mainly controlled by three key soil properties: acidity, clay, and organic carbon contents. Thus, altitude-specific land-use management holds significance in the distribution of available soil micronutrients in hilly ecosystems.

Data article on soil site suitability analysis using geostatistical and visualization techniques for selected winter crops in Sagar island, India.

We assessed soil site suitability for selected winter crops in the coastal saline agro-ecological environment of Sagar Island, India by integrating land limitation and crop suitability evaluation framework of FAO. Grid based (1 km by 1 km) soil sampling and estimation of important soil quality attributes were measured in the laboratory following standard procedures. Geo-statistical and visualization methods were applied to match the soil suitability for selected crops. The weights of crop specific soil parameters have been assigned through PCA analysis. The inverse distance weighting interpolation and reclassification methods were adopted for generation of spatial layers of those soil attributes. Nearly 61% area (14,618 ha GA) of the Island is under agricultural landuse (AL), mostly dominated (>75% of AL) by lowland rice-fallow mono-cropping. Soils are highly suitable (S1) for growing sunflower while moderately suitable (S2) for growing chilli, mustard and potato crops. The grid-wise georeferenced soil data information generated in this study will help in periodic monitoring of soil quality in spatio-temporal dimensions for devising location specific soil health managements in the Island. The methodology used in estimating soil quality index and crop specific soil suitability analysis in spatial format will help in replicating such studies in other such coastal Islands of Indian Sub-continent.

Acid drainage from coal mining: Effect on paddy soil and productivity of rice.

Overburden and acid drainage from coal mining is transforming productive agricultural lands to unproductive wasteland in some parts of Northeast India. We have investigated the adverse effects of acid mine drainage on the soil of rice paddy and productivity by comparing them with non-mined land and abandoned paddy fields of Jaintia Hills in Northeast India. Pot experiments with a local rice cultivar (Myngoi) as test crop evaluated biological productivity of the contaminated soil. Contamination from overburden and acid mine drainage acidified the soil by 0.5 pH units, increased the exchangeable Al3+ content 2-fold and its saturation on clay complexes by 53%. Available sulfur and extractable heavy metals, namely Fe, Mn and Cu increased several-fold in excess of critical limits, while the availability of phosphorus, potassium and zinc contents diminished by 32-62%. The grain yield of rice was 62% less from fields contaminated with acid mine drainage than from fields that have not suffered. Similarly, the amounts of vegetation, i.e. shoots and roots, in pots filled with soil from fields that received acid mine drainage were 59-68% less than from uncontaminated land (average shoot weight: 7.9±2.12gpot-1; average root weight: 3.40±1.15gpot-1). Paddy fields recovered some of their productivity 4years after mining ceased. Step-wise multiple regression analysis affirmed that shoot weight in the pots and grain yield in field were significantly (p<0.01) and positively influenced by the soil's pH and its contents of K, N and Zn, while concentration of S in excess of threshold limits in contaminated soil significantly (p<0.01) reduced the weight of shoots in the pots and grain yield in the field.