Rice-based integrated farming system improves the soil quality, bacterial community structure and system productivity under sub-humid tropical condition

Rice-based integrated farming system improves the productivity and profitability by recycling resources efficiently. In the sub-humid tropics, rice production without sufficient nutrient replenishment often leads to soil health and fertility degradation. There has been very limited research on soil health and fertility after adopting a multi-enterprising rice-based integrated farming system (IFS), notably in the rice-fish-livestock and agroforestry system, when compared to a conventional farming system (CS). Therefore, the present study analyzed the dynamics of soil properties, soil bacterial community structure and their possible interaction mechanisms, as well as their effect on regulating soil quality and production in IFS, IFSw (water stagnant area of IFS) and CS. The results indicated that soil nutrient dynamics, bacterial diversity indices (Shannon index, Simpson index, Chao 1, ACE and Fisher index) and system productivity were higher in IFSw and IFS compared to CS. Moreover, relative operational taxonomic units of dominant bacterial genera (Chloroflexi, Acidobacteria, Verrucomicrobia, Planctomycetes, Cyanobacteria, Crenarchaeota and Gemmatimonadetes) were also higher in IFSw and IFS compared to CS. Mean soil quality index (SQI) was highest in IFSw (0.780 ± 0.201) followed by IFS (0.770 ± 0.080) and CS (0.595 ± 0.244). Moreover, rice equivalent yields (REY) and rice yields were well correlated with the higher levels of soil biological indices (SQIBiol) in IFS. Overall, our results revealed that rice-based IFS improved the soil health and fertility and ensuing crop productivity through positive interaction with soil bacterial communities and nutrient stoichiometry leading to agroecosystem sustainability.

Cyanobiont diversity in six Azolla spp. and relation to Azolla-nutrient profiling

Illumina-Miseq^®-based cyanobiont diversity and biomass were analyzed in six Azolla spp. Results revealed that 93-98% of total operational taxonomic units (OTUs) belong to Nostacaceae followed by Cylindrospermopsis with about 1-6% OTUs. The taxonomy of Azolla-cyanobiont is a long-term debate within the scientific community. Morphological and biochemical-based reports indicated the presence of Anabaena, Nostoc and/or Trichormus azollae as abundant Azolla-cyanobionts, however, molecular data did not support the abundance of Anabaena and/or Nostoc. To understand furthermore, the cyanobiont diversity in six species of Azolla (A. microphylla, A. mexicana, A. filiculoides, A. caroliniana, A. pinnata and A. rubra) was analyzed based on 16S rRNA Illumina-MiSeq sequencing. Additionally, biomass and nutrient profiling of Azolla spp. were analyzed and correlated with cyanobiont diversity. Illumina-MiSeq data revealed that 99.6-99.9% of total operational taxonomic units (OTUs) belonged to Nostocophycideae (class), Nostocales (order) and Nostacaceae (family). At genus level, the unassigned affiliation (93.4-97.9%) under Nostacaceae family was abundant followed by Cylindrospermopsis OTUs (1.1-6.0%). Interestingly, A. pinnata harboured maximum Cylindrospermopsis OTUs and also recorded higher biomass (40.67 g m^-2 day^-1), whereas crude protein (25.9%) and antioxidants (76.9%) were recorded to be higher in A. microphylla. Biplot analysis revealed that A. pinnata and its cyanobiont abundance were positively correlated with neutral and acid detergent fibers. Overall, the present findings deepened the understanding about cyanobiont in Azolla and its relations with Azolla nutrient profiling.

Ecosystem services in different agro-climatic zones in eastern India: impact of land use and land cover change

Land use and land cover (LULC) change have considerable influence on ecosystem services. Assessing change in ecosystem services due to LULC change at different spatial and temporal scales will help to identify suitable management practices for sustaining ecosystem productivity and maintaining the ecological balance. The objective of this study was to investigate variations in ecosystem services in response to LULC change over 27 years in four agro-climatic zones (ACZ) of eastern India using satellite imagery for the year 1989, 1996, 2005, 2011 (Landsat TM) and 2016 (Landsat 8 OLI). The satellite images were classified into six LULC classes, agriculture land, forest, waterbody, wasteland, built-up, and mining area. During the study period (1989 to 2016), forest cover reduced by 5.2%, 13.7%, and 3.6% in Sambalpur, Keonjhar, and Kandhamal districts of Odisha, respectively. In Balasore, agricultural land reduced by 17.2% due to its conversion to built-up land. The value of ecosystem services per unit area followed the order of waterbodies > agricultural land > forests. A different set of indicators, e.g., by explicitly including diversity, could change the rank between these land uses, so the temporal trends within a land use are more important than the absolute values. Total ecosystem services increased by US$ 1296.4 × 10⁵ (50.74%), US$ 1100.7 × 10⁵ (98.52%), US$ 1867 × 10⁵ (61.64%), and US$ 1242.6 × 10⁵ (46.13%) for Sambalpur, Balasore, Kandhamal, and Keonjhar, respectively.

Effect of Abiotic Factors on Degradation of Imidacloprid

The role of soil moisture, light and pH on imidacloprid dissipation was investigated. A high performance liquid chromatography (HPLC) based method was developed to quantify imidacloprid present in soil with a recovery of more than 82%. Rate of dissipation of imidacloprid from soil was faster in submerged condition compared to field capacity and air dried condition. Imidacloprid dissipated non-significantly between sterile and non-sterile soils, but at field capacity, the dissipation was faster in non-sterile soil compared to sterile soil after 60 days of incubation. Similarly, under submergence, the dissipation of imidacloprid was 66.2% and 79.8% of the initial in sterile and non-sterile soils, respectively. Imidacloprid was rather stable in acidic and neutral water but was prone to photo-degradation. Therefore, imidacloprid degradation will be faster under direct sunlight and at higher soil moisture.