Management practices for control of runoff losses from cotton furrows under storm rainfall. III. Cover and wheel traffic effects on nutrients (N and P) in runoff from a black Vertosol

Abstract

Transport of nitrogen (N) and phosphorus (P) in runoff was measured using a rainfall simulator on a cotton hill–furrow system with a range of on-ground cover (0–60%), each with and without prior wheel traffic in the furrow. Total N and P losses in runoff (kg/ha) from the bare plots on a whole-field basis (wheel and non-wheel tracks) were equivalent to 1.5% and 1%, respectively, of fertiliser applied that season (218 kg N/ha, 27 kg P/ha). This was for a single runoff event of 17 mm, about 1/10 of the total runoff expected in a season. Retaining surface cover and avoiding wheel traffic were both effective in reducing runoff losses of total N and P, especially when used together. Retaining cover gave considerably lower concentrations of total P, and of N and P associated with sediment, with no significant differences (P > 0.05) between wheel and non-wheel tracks. The majority of nutrients were transported with sediment, for P for all treatments, and for N from low cover plots. Concentrations of dissolved N, dominantly as NO3-N, were unaffected by cover on non-wheel tracks but increased with cover on wheel track plots where runoff occurred as shallow interflow. On a whole-field basis, N was mainly in dissolved form at higher covers, because most runoff came from wheel tracks where interflow occurred. Reducing the ratio of wheel tracks to non-wheel tracks will reduce runoff of N and P. Interflow or exfiltration above an infiltration throttle layer is a worst-case scenario for runoff transport of soluble, poorly sorbed chemicals such as NO3-N, which would otherwise leach and not enter runoff. To improve water quality, for both sorbed and dissolved forms, the combination of retaining cover and avoiding wheel traffic and subsoil compaction is needed. Similarly, land uses involving high nutrient inputs should be avoided on soils with shallow subsurface restrictions to infiltration, which are thus prone to interflow. Primary (dispersed) clay and silt were slightly enriched in sediment in runoff, while primary fine and coarse sand were depleted. However, sediments were not enriched in total N and P compared with the soil surface, and organic carbon was only slightly enriched (enrichment ratio 1.06). This is typical of the behaviour of well-aggregated soils of high clay content.

Effects of subsurface drip irrigation rates and furrow irrigation for cotton grown on a vertisol on off-site movement of sediments, nutrients and pesticides

“…The furrow runoff carried more than 10% of the applied trifluralin which contrasts with data of Leonard et al (1979) that showed only a small proportion of the applied trifluralin in run-off. Total trifluralin loss in run-off was strongly related to run-off volume rather than to concentrations in that run-off because the soil sorption index for trifluralin is very high (8000 Koc) (Silburn and Glanville, 2002). Trifluralin movement in the runoff has been reported to vary greatly due to sediment load, sediment type, formulation used, amount and duration of irrigation and canopy cover than solely on the method of irrigation (Wauchope, 1978).…”

“…In spite of lower runoff from subsurface 90 and 120% ETc compared to furrow, greater prometryn movement was primarily caused by higher concentration in the runoff associated with the drip irrigation treatments. Silburn and Glanville (2002) showed that the transport of prometryn was largely in the water phase rather than in sediments from a cotton field. As the run-off from the subsurface drip irrigation contained less suspended sediment but more concentrated water than the furrow plots in our trial, it resulted in a greater amount of prometryn movement from the subsurface drip irrigation than furrow treatments.…”

Spatio-temporal patterns in land use and management affecting surface runoff response of agricultural catchments—A review

“…These wheel tracks have reduced infiltration capacity, creating a small-scale variability in infiltrability; they restrict subsurface flow and increase return flow and they redirect surface runoff (Tullberg et al, 2001, Green et al, 2003, Silburn and Hunter, 2009. Tillage is intended to remove these adverse effects of wheeling and provide other positive effects, such as incorporation of residues and seeds.…”

Towards Sustainable Land Use in Vertisols in Kenya: Challenges and Opportunities

“…In Queensland, Australia, zero tillage and no-traffic were observed to minimize environmental degradation effects including soil erosion while increasing grain yield. Further, the amount of rain required to initiate run-off in irrigated cotton was increased by retaining crop residues and other materials that increased soil cover while perennial pasture rotations improved soil fertility (Silburn and Glanville, 2002;Armstrong et al, 2003). Land forming for surface water drainage: Poor drainage is a major problem in Vertisols due to water logging of early planted crops; thus, universally, Vertisols are cropped post-rain season with plant growth being sustained largely by residual soil MC.…”