Cornstarch-based, Biodegradable Superabsorbent Polymer to Improve Water Retention, Reduce Nitrate Leaching, and Result in Improved Tomato Growth and Development

In arid and semi-arid climates, water scarcity and nutrient availability are major constraints for food production. Excess fertilization to make up for the limited nutrient availability in dry soils leads to nitrogen runoff and groundwater contamination. Reducing nitrogen leaching into surface water while providing adequate nutrition remains a major challenge. Superabsorbent polymers (SAPs) can reduce water loss and improve nutrient retention and therefore minimize leaching and increase crop yields. SAPs are made from petroleum or natural products, but plant-based SAPs have been gaining popularity because they have fewer long-term effects on the environment. However, there is little known about how SAPs made from cornstarch effect plant growth and production in tomatoes. So, we evaluated total nitrogen and water retention in SAP-treated soils and evaluated their effects on growth and development of tomatoes (Solanum lycopersicum). Soils were amended with different rates of cornstarch-based SAP (i.e., 0 kg SAP, 0 kg SAP+N, 0.5 kg SAP+N, 1 kg SAP+N, 1.5 kg SAP+N, and 2 kg SAP+N). Results indicate that the mean volume of water and nitrates retained in the soils amended with cornstarch-based SAPs increased with increasing rate of SAP. The treatment containing the highest dose (i.e., 2 kg SAP) decreased the amount of leachate and nitrates from soil 79.34% and 93.11% at 3 days after fertilization (DAF) and 78.84% and 81.58% at 9 DAF in comparison with the soil-only and fertilizer-only treatments, respectively. The results also indicate cornstarch-based SAP significantly improved plant growth and yield parameters compared with the treatments without SAP. Furthermore, the greatest number of leaves, flowers, fruits, and dry matter production were found in the 1-kg SAP treatment. Therefore, application of cornstarch-based SAPs can improve tomato production in times of drought stress by retaining more water and nutrients in the active rooting zone and can reduce environmental pollution by reducing nitrogen runoff.

Are agricultural support policies harmful to the environment? Evidence from Japanese farm-level policy simulation

This study presents the environmental impacts of agricultural policy instruments as evidence from an ex-ante farm-level policy simulation model in Japan. Simulations did indicate that all types of agri-environmental payments achieved the environmental benefit for the land studied. Conversely, market price support does not inevitably increase nitrogen runoff or greenhouse gas emissions at any time since paddy fields themselves have the function of purifying water pollution and work as a biodiversity nursery. The direction and magnitude of the policy impacts are an empirical matter that should be considered carefully at a local level.

Dynamics and Uncertainty in Land Use Conversion for Perennial Energy Crop Production: Exploring Effects of Payments for Ecosystem Services Policies

Perennial energy crops like switchgrass that are used for biofuel production have the potential to generate various water quality benefits such as reduced nitrogen runoff. Yet the current expected returns to switchgrass are not profitable enough for these crops to be widely adopted by U.S. farmers due to relatively unstable yields, volatile revenues, and high costs of crop establishment. This study uses a dynamic economic model to investigate the uncertainties in the yields and costs of switchgrass production, in comparison with those of corn-soybeans in the Chesapeake Bay Watershed in Pennsylvania. Results indicate that farmers would be willing to convert corn-soybeans to switchgrass land use with the provision of payments for ecosystem services (PES). A targeted PES policy based on the environmental effectiveness of the crop land is found to be slightly more effective in providing nitrogen reductions than a uniform PES policy with cost savings of 8–19%. Moreover, switchgrass has the potential of providing energy supply while reducing greenhouse gases emissions.