Impacts of water and residue managements on indicators of soil health in rice paddies
Date
2024
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Publisher
University of Delaware
Abstract
Rice agroecosystems are crucial globally, feeding half the population and being economically significant in the USA. Effective rice paddy soil management is essential for maintaining soil health, but soil health indicators have not been developed for or evaluated in rice systems. Rice typically grows under various flooded conditions, but altering water levels through periodic drainage can influence key biological, physical, and chemical soil health indicators. Similarly, incorporating rice residues like straw and husk can also affect soil health indicators. This study examined the effects of water and rice residue management on rice soil health. The water treatments were non-flooded, continuously flooded, and both moderate and extreme alternate wetting and drying (AWD 15 and AWD 30, respectively), while residue treatments included a nonamended control and amendments of rice straw, charred straw, or rice husk. Conducted over two crop cycles at the University of Delaware Rice Investigation, Communication, and Education (RICE) Facility, each treatment was replicated in three rice paddy mesocosms. Bulk soil samples from these mesocosms were analyzed for physical, chemical, and biological health indicators, comparing pre-treatment conditions (time 1, T1) to those after one (time 2, T2) and two (time 4, T4) crop cycles. In addition, porewater parameters and CH4 fluxes were evaluated. Treatments resulted in differences in CH4 fluxes and soil organic matter (SOM) content, with paddies receiving straw amendments having higher CH4 emissions and SOM content. We also noted a trend toward higher CH4 fluxes with more intense water inundation. Using the Comprehensive Assessment of Soil Health (CASH) model, an overall soil health score was computed relative to the pre-treatment baseline. Furthermore, each soil health score was computed relative to the respective controls at T4. Over two years, while the overall soil health score showed no significant changes, individual indicators varied with different treatments. The additional analysis of soil health indicators at T4 relative to the T4 controls revealed that straw amendment notably improved the overall soil health score, primarily due to increased soil C despite higher CH4 emissions. This result underscores the need for further research into methods that minimize CH4 emissions from rice paddies without adversely affecting soil health. Future studies should explore the long-term impacts of water management strategies and soil amendments, considering soil and environmental variability and the timing of sample collection.
Description
Keywords
Residue management, Water management, Soil health, Rice paddy