Rice field drainage affects nitrogen dynamics and management

Abstract

Many California rice growers are now using foliar-active herbicides that require fields to be drained before application. Current regulations limit aerial herbicides and they must be applied by ground, requiring a soil surface dry enough to support application equipment. Our research showed that draining rice fields for a prolonged period early in the season led to a buildup of nitrate in the soil. About 60% of this nitrogen was lost when the field was reflooded, reducing nitrogen-use efficiency and uptake, and lowering grain yields. Nitrate-nitrogen accumulated at a rate of about 1.8 pounds per acre daily, and accumulation began about 4 days after the field was drained. During a typical drain of 10 to 14 days, about 20 pounds of nitrate-nitrogen per acre can be lost. Field experiments showed that incorporating fertilizer nitrogen into the subsurface soil increases nitrogen-use efficiency. Based on this research, we recommend that growers incorporate as much of their preplant nitrogen as possible below the soil surface and limit the drain period as much as possible.

Nitrogen Management and Methane Emissions in Direct‐Seeded Rice Systems

“…To quantify potential soil N denitrification losses, preseason soil sampling events occurred before and after irrigation flushes for stale seedbeds. By using this approach, it was assumed that the majority of NO 3 –N that accumulated before flooding was lost through denitrification processes as soils became anaerobic (Linquist et al, 2011). Two factors supporting this assumption were the low hydraulic conductivity of rice soils in this region (0.007–0.074 cm d −1 ) resulting in minimal leaching losses (X.Q.…”

“…Furthermore, Patrick and Wyatt (1964) reported that total soil N losses increased when soils alternated between aerobic and anaerobic conditions. This is likely a result of nitrification processes occurring when soils dry down followed by denitrification losses when soils are flooded (George et al, 1993; Linquist et al, 2011). In the present study, it was hypothesized that indigenous soil denitrification losses caused by stale seedbed flushes may be contributing to decreased soil N availability, which in turn may increase fertilizer N requirements for stale seedbed as compared with conventional rice production systems.…”

Abiotic partitioning of clothianidin under simulated rice field conditions

“…In California, rice fields are flooded prior to planting, and water levels are maintained throughout the growing season, although fields may be drained for up to 3 weeks soon after planting in order to apply pesticides. 7 Discharged field water flows directly into the Sacramento River Basin (SRB), a system of lakes, streams and rivers supporting a variety of aquatic species that are crucial to the economic and environmental health of the state. Clothianidin has been classified as highly toxic to sediment-dwelling organisms such as Mysidopsis bahia, Chironomus riparius and Leptocherius plumulosus.…”

Evaluation of nitrogen balance in a direct-seeded-rice field experiment using Hydrus-1D

“…Zhang et al (2011a,b) also reported that the nitrification decreased and denitrification increased with soil depth (in 0-20 cm) in DSR experimental fields. When soil is subjected to aerobic-anaerobic cycles, nitrate concentrations tend to increase during aerobic periods but then rapidly decrease when fields are flooded, with soil nitrate presumably lost due to denitrification (Becker et al, 2007;Linquist et al, 2011).…”