Rice residue promotes mobilisation and plant acquisition of soil phosphorus under wheat (Triticum aestivum)-rice (Oryza sativa) cropping sequence in a semi-arid Inceptisol.

Disposal of significant tonnages of rice straw is expensive, but using it to mobilise phosphorus (P) from inorganically fixed pools in the soil may add value. This study was carried out to determine whether the use of rice straw mixed with phosphorus-solubilizing microbes could solubilize a sizable portion fixed soil P and affect P transformation, silicon (Si) concentration, organic acid concentrations, and enzyme activity to increase plant growth. Depending on the soil temperature, the application of rice straw at 12 Mg ha-1 with phosphorus-solubilizing microbes could solubilize 3.4-3.6% of inorganic P, and minimised the hysteresis impact by 6-8%. At plant maturity, application of rice straw at 12 Mg ha-1 with phosphorus-solubilizing microbes and 75% of recommended P application raised the activity of dehydrogenase, alkaline phosphatase activity, cellulase, and peroxidase by 77, 65, 87, and 82% in soil, respectively. It also boosted Si concentration in the soil by 58%. Wheat grain yield was 40% and 18% higher under rice straw at 12 Mg ha-1 with phosphorus-solubilizing microbes with 75% of recommended P application than under no and 100% P application, respectively. Rice grain yield also increased significantly with the same treatment. Additionally, it increased root volume, length, and P uptake by 2.38, 1.74 and 1.62-times above control for wheat and 1.98, 1.67, and 2.06-times above control for rice, respectively. According to path analysis, P solubilisation by Si and organic acids considerably increased (18-32%) P availability in the rhizosphere. Therefore, cultivators could be advised to use rice straw at 12 Mg ha-1 with phosphorus-solubilizing microbes with 75% P of mineral P fertiliser to save 25% P fertiliser without reducing wheat and rice yield.

Priming maize seeds with cyanobacteria enhances seed vigour and plant growth in elite maize inbreds.

Biofilm formation of a nitrogen-fixing cyanobacterium Anabaena torulosa with a beneficial fungus Trichoderma viride (An-Tr) was examined under laboratory conditions. A gradual enhancement in growth over A. torulosa alone was recorded in the biofilm, with 15-20% higher values in nitrogen fixation, IAA and exopolysaccharide production illustrating the synergism among the partners in the biofilm. To investigate the role of such biofilms in priming seed attributes, mesocosm studies using primed seeds of two maize inbred lines (V6, V7) were undertaken. Beneficial effects of biofilm (An-Tr) were recorded, as compared to uninoculated treatment and cyanobacterial consortium (Anabaena-Nostoc; BF 1-4) at both stages (7 and 21 DAS, days after sowing) with a significant increase of more than 20% in seedling attributes, along with 5-15% increment in seed enzyme activities. More than three- to fivefold higher values in nitrogen fixation and C-N mobilizing enzyme activities, and significant increases in leaf chlorophyll, proteins and PEP carboxylase activity were observed with V7-An-Tr biofilm. Cyanobacterial inoculation brought about distinct changes in the soil phospholipid fatty acid profiles (PLFA); particularly, significant changes in those representing eukaryotes and anaerobic bacteria. Principal component analyses illustrated the significant role of dehydrogenase activity and microbial biomass carbon and distinct elicited effects on soil microbial communities, as evidenced by the PLFA. This investigation highlighted the promise of cyanobacteria as valuable priming options to improve mobilization of nutrients at seed stage, modulating the abundance and activities of various soil microbial communities, thereby, enhanced plant growth and vigour of maize plants.

Assessment of soil health parameters and application of the sustainability index to fields under conservation agriculture for 3, 6, and 9 years in India.

The effect of duration of conservation agriculture adoption on soil carbon dynamics and system sustainability was evaluated on farms of 30 villages in the Nilokheri block of Karnal district, Haryana, India. Sustainability was evaluated, in which a number of soil physical, chemical, and biological parameters were measured and a Sustainability Index (SI) was applied. Soil samples were collected from existing conservation agriculture (CA) and conventional tillage (CT) farms. Villages under CA practices were subdivided as CA3, CA6, and CA9 based on the number of years of CA practice adoption. Results showed that bulk density (BD) of 0-15 cm soil depth was 7% greater in CA3 plots, whereas in CA6 and CA9 plots BD values were only 2% and 3% higher than CT. Soil organic carbon (SOC) in 0-15 cm soil depth was found to be greater by 16.32% in CA3 than CT plots, whereas SOC was higher by 38.77% and 61.22% in CA6 and CA9. In CA, for the 0-15 and 15-30 cm soil depths, labile pools were 36% and 22% greater than CT, respectively. For both the soil depths in CA, the recalcitrant pool was 12% and 9% more than CT, respectively. Microbial biomass carbon (MBC) values of the 0-15 cm soil depth were increased over CT by 18.57%, 47.08%, and 71.5% for CA3, CA6, and CA9 respectively. In CA plots, the SI of 0-15 cm soil depth ranged between cumulative ratings (CR) of 18-21, which indicates that CA practice is "sustainable" for both soil depths. For CT, CR ranged from 25 to 30 for both soil depths resulting in a SI of "sustainability with high input". Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) scores showed that SOC had the maximum weight (0.96) towards sustainability, giving it a rank of 1. Effective rooting depth (ERD), BD, texture, and wilting point (WP) ranked 2, 3, 4 and 5, respectively, indicating their corresponding weight of contribution towards the SI. Farmers in the Karnal district should be encouraged to adopt CA practices as they can increase SOC and move the systems from "sustainable with high input" to "sustainable".