The cytoprotective co-chaperone, AtBAG4, supports increased nodulation and seed protein content in chickpea without yield penalty.

Drought and extreme temperatures significantly limit chickpea productivity worldwide. The regulation of plant programmed cell death pathways is emerging as a key component of plant stress responses to maintain homeostasis at the cellular-level and a potential target for crop improvement against environmental stresses. Arabidopsis thaliana Bcl-2 associated athanogene 4 (AtBAG4) is a cytoprotective co-chaperone that is linked to plant responses to environmental stress. Here, we investigate whether exogenous expression of AtBAG4 impacts nodulation and nitrogen fixation. Transgenic chickpea lines expressing AtBAG4 are more drought tolerant and produce higher yields under drought stress. Furthermore, AtBAG4 expression supports higher nodulation, photosynthetic levels, nitrogen fixation and seed nitrogen content under well-watered conditions when the plants were inoculated with Mesorhizobium ciceri. Together, our findings illustrate the potential use of cytoprotective chaperones to improve crop performance at least in the greenhouse in future uncertain climates with little to no risk to yield under well-watered and water-deficient conditions.

Effects of hydrochar derived from hydrothermal treatment of sludge and lignocellulose mixtures on soil properties, nitrogen transformation, and greenhouse gases emissions.

In this study, hydrochar samples derived from hydrothermal treatment (HTT) of sludge and sludge-biomass mixtures were applied to a sandy soil and their effects on soil properties, soil nutrients, greenhouse gas (GHG) emissions, and soluble heavy metals were investigated. The application of untreated sludge and hydrochar derived from HTT of sludge at 180 °C led to the highest soluble nitrate, CO2 and N2O emissions, followed by the application of hydrochar samples derived from HTT of sludge-biomass mixtures at 180 °C. Although the application of hydrochar samples derived from HTT of sludge alone and sludge-biomass mixtures at 240 °C in sandy soil led to the lowest emissions of CO2 and N2O, it resulted in lower levels of soil electrical conductivity (EC), cation exchange capacity (CEC) and soluble phosphorus. The application of hydrochar samples derived from HTT at 240 °C led to the production of CH4 and lower nitrate-N contents than hydrochar samples derived from HTT at 180 °C. These results indicated that the soils containing hydrochar samples from HTT at 240 °C were anaerobic, which might inhibit the growth of plants. The application of hydrochar samples derived from HTT of sludge-biomass at 180 °C led to significantly improved contents of soil soluble phosphorus (2.56 and 2.84 g kg-1 soil) and soil nitrate-N (160.2 and 263.2 mg kg-1 soil) at the end of 60 days of incubation. However, these contents were lower than the contents of soluble phosphorus (3.71 and 4.45 g kg-1 soil) and nitrate-N (528.3 and 583.2 mg kg-1 soil) with the application of untreated sludge and sludge derived from HTT of sludge alone at 180 °C. Although more studies are needed to understand the mechanisms and effects on different soils, this study provides useful insights into the application of hydrochar derived from sludge-biomass mixture in soil.

Environmental and economic trade-offs of using composted or stockpiled manure as partial substitute for synthetic fertilizer.

Manure generated from livestock production could represent an important source of plant nutrients in substitution of synthetic fertilizer. To evaluate the sustainability of partially substituting synthetic fertilizer with soil organic amendments (OAs) in horticulture, an economic and greenhouse gas (GHG) budget was developed. The boundary for analysis included manure processing (stockpiling vs. composting) and transport and spreading of manure and compost (feedlot and chicken) in intensively cultivated horticultural fields. The OA field application rates were calculated based on the nitrogen supplied by OAs. The GHG budget based on directly measured emissions indicates that the application of composted manure, in combination with reduced fertilizer rate, was always superior to stockpiled manures. Compost treatments showed from 9 to 90% less GHG emissions than stockpiled manure treatments. However, higher costs associated with the purchase and transport of composted manure (three times higher) generated a greater economic burden compared with stockpiled manure and synthetic fertilizer application. The plant nutrient replacement value of the OAs was considered only for the first year of application, and if long-term nutrient release from OAs is taken into account, additional savings are possible. Because the income from soil carbon sequestration initiatives in response to OA application is unlikely to bridge this financial gap, particularly in the short term, this study proposes that future policy should develop methodologies for avoided GHG emissions from OA application. The combined income from soil carbon sequestration and potentially avoided GHG initiatives could incentivize farmers to adopt OAs as a substitute for synthetic fertilizers, thereby promoting more sustainable farming practices.

Effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N-turnover, the N2O reductase-gene nosZ and N2O:N2 partitioning from agricultural soils.

Nitrification inhibitors (NIs) have been shown to reduce emissions of the greenhouse gas nitrous oxide (N2O) from agricultural soils. However, their N2O reduction efficacy varies widely across different agro-ecosystems, and underlying mechanisms remain poorly understood. To investigate effects of the NI 3,4-dimethylpyrazole-phosphate (DMPP) on N-turnover from a pasture and a horticultural soil, we combined the quantification of N2 and N2O emissions with 15N tracing analysis and the quantification of the N2O-reductase gene (nosZ) in a soil microcosm study. Nitrogen fertilization suppressed nosZ abundance in both soils, showing that high nitrate availability and the preferential reduction of nitrate over N2O is responsible for large pulses of N2O after the fertilization of agricultural soils. DMPP attenuated this effect only in the horticultural soil, reducing nitrification while increasing nosZ abundance. DMPP reduced N2O emissions from the horticultural soil by >50% but did not affect overall N2 + N2O losses, demonstrating the shift in the N2O:N2 ratio towards N2 as a key mechanism of N2O mitigation by NIs. Under non-limiting NO3- availability, the efficacy of NIs to mitigate N2O emissions therefore depends on their ability to reduce the suppression of the N2O reductase by high NO3- concentrations in the soil, enabling complete denitrification to N2.

Mobile continuous-flow isotope-ratio mass spectrometer system for automated measurements of N2 and N2O fluxes in fertilized cropping systems.

The use of synthetic N fertilizers has grown exponentially over the last century, with severe environmental consequences. Most of the reactive N will ultimately be removed by denitrification, but estimates of denitrification are highly uncertain due to methodical constraints of existing methods. Here we present a novel, mobile isotope ratio mass spectrometer system (Field-IRMS) for in-situ quantification of N2 and N2O fluxes from fertilized cropping systems. The system was tested in a sugarcane field continuously monitoring N2 and N2O fluxes for 7 days following fertilization using a fully automated measuring cycle. The detection limit of the Field-IRMS proved to be highly sensitive for N2 (54 g ha-1 day-1) and N2O (0.25 g ha-1 day-1) emissions. The main product of denitrification was N2 with total denitrification losses of up to 1.3 kg N ha-1 day-1. These losses demonstrate sugarcane systems in Australia are a hotspot for denitrification where high emissions of N2O and N2 can be expected. The new Field-IRMS allows for the direct and highly sensitive detection of N2 and N2O fluxes in real time at a high temporal resolution, which will help to improve our quantitative understanding of denitrification in fertilized cropping systems.