No-tillage effects on N and P exports across a rice-planted watershed

Abstract

No tillage (NT) can be used as a management tool to alleviate the negative effects of agricultural practices on the environment by reducing the runoff volume and nutrient exports. The main objective of this research was to quantify the effect of NT on nitrogen (N) and phosphorus (P) exports across a rice-planted watershed using the soil and water assessment tool (SWAT) model. Results show that total N and P runoff exports from rice fields across the watershed ranged from 7.2 to 22.8 kg N/ha and 0.56 to 6.80 kg P/ha, respectively, over five rice-growing seasons under conventional tillage (CT) practice. The adoption of NT reduced the runoff volume, and the total N and total P exports by 25.9, 8.5, and 7.8 %, respectively, compared with the total exports under CT practice in the same study area. Rice yields were reduced by 0.7-1.9 % within the first 4 years after the adoption of NT, but began to rise in the fifth year. These results suggest that a long-term period of NT practice is necessary to reduce N and P exports without comprising the rice yield on rice-planted watersheds. In addition, the benefits of implementing NT practice alone were limited, and other practices, such as water and nutrient management, should be combined with NT practice.

Sustainable Conservation Tillage Improves Soil Nutrients and Reduces Nitrogen and Phosphorous Losses in Maize Farmland in Southern China

“…The reason for the low levels of N and P movement along the soil profile under the conservation tillage technique was probably due to the latter's ability to reduce surface runoff and infiltration, thereby allowing most of the nutrients to be concentrated at the 0-20 cm soil depth. According to Liang et al [34], a decrease in runoff was observed in the NT system compared with the CT system, ranging from 16.0 to 37.3% (average 25.9%), from 2008 to 2012, demonstrating a declining rate. The corresponding rates of TN and TP exports varied from 4.1 to 16.9% (average 8.5%) and from 5.6 to 10.3% (average 7.8%), respectively, for NT compared with results for CT [34].…”

“…According to Liang et al [34], a decrease in runoff was observed in the NT system compared with the CT system, ranging from 16.0 to 37.3% (average 25.9%), from 2008 to 2012, demonstrating a declining rate. The corresponding rates of TN and TP exports varied from 4.1 to 16.9% (average 8.5%) and from 5.6 to 10.3% (average 7.8%), respectively, for NT compared with results for CT [34]. The soil TN, NO 3…”

“…A substantial body of research exists on subsurface P transport, with macropore flow considered the primary pathway of transport by passing the reactive matrix of the subsoil [36]. According to Liang et al [34], runoff is the main carrier of soil nutrients, and so a decrease in runoff volume will lead to a decrease in nutrient movement. In that study, the conservation tillage technique recorded an average N loss of 3.07 kg•ha −1 in runoff compared to 3.39 kg•ha −1 recorded by CT. Average TP loss recorded under conservation tillage techniques was 5.93 kg•ha −1 compared to CT with 7.37 kg•ha −1 .…”

“…This represents a 9.4 and 19.53% TN and TP reduction in runoff loss under conservation tillage techniques compared to CT. The least TN and TP in runoff losses was recorded by NTTS compared to the rest of the conservation tillage techniques and the CT. Conservation tillage could only prevent some of the N and P escaping from the surface soil; in contrast, some N in the form of organic N, or P in the form of soluble P, might have greater leaching potential under conservation tillage technique than under CT practice [34]. Indeed, P leaching has been documented in a wide array of soils, from fine to coarse textured [36], although the inherent integrity and continuity of macropores can profoundly affect P leaching potential, particularly for applied sources [37,38].…”

Recent advances in control technologies for non-point source pollution with nitrogen and phosphorous from agricultural runoff: current practices and future prospects

“…For example, Clausen et al studied tillage effects on runoff for croplands in Vermont, USA, and found that reduced tillage reduced runoff by 64% [45]. Liang et al reported that runoff volume from rice-planting watersheds was reduced by 25.9% using no-tillage techniques [46]. Reduced tillage and no-tillage reduce the intensity of tillage practices as well as the impact of rain by the protection of soil surface using crop residues.…”