Grass Buffer Strips Improve Soil Health and Mitigate Greenhouse Gas Emissions in Center-Pivot Irrigated Cropping Systems

Declining water resources and soil degradation have significantly affected agricultural sustainability across the world. In the southern High Plains of USA, buffer strips of perennial grasses alternating with cultivated corn strips were introduced in center-pivot irrigated crop fields to increase agronomic production and ecosystem services. A study was conducted to evaluate soil carbon (C) and nitrogen (N) dynamics, greenhouse gas (GHG) emissions, and soil health benefits of integrating circular grass buffer strips in the center-pivot irrigated corn production system. Multiple parameters were assessed in the grass buffer strips, and at distances of 1.52, 4.57, and 9.14 m away from the edges of grass strips in corn strips. While grasses in the buffer strips depleted N compared to corn strips, potential C mineralization (PCM) was 52.5% to 99.9% more in grass strips than in corn strips. Soil microbial biomass C (MBC) content was 36.7% to 52.5% greater in grass strips than in corn strips. Grass buffer also reduced carbon dioxide (CO2) and nitrous oxide (N2O) emissions from corn strips. Grass buffer strips can improve soil health and sustainability in center-pivot irrigated cropping systems by increasing soil C components and reducing GHG emissions.

Influence of mowing and narrow grass buffer widths on reductions in sediment, nutrients, and bacteria in surface runoff

Miller, J. J., Curtis, T., Chanasyk, D. S. and Reedyk, S. 2015. Influence of mowing and narrow grass buffer widths on reductions in sediment, nutrients, and bacteria in surface runoff. Can. J. Soil Sci. 95: 139–151. Little research has been conducted on the effect of mowing and buffer width on the effectiveness of short-width (< 10 m) native grass buffers to filter sediment, nutrients, and bacteria. A 2-yr (2011–2012) field study was conducted on native rangeland in southern Alberta. The treatments of mowing and buffer width (1.5, 3, 6 m) were evaluated using a randomized complete block design with four replicates. The buffer plots were pre-wet with distilled water. A spiked solution was then applied to each plot using a run-on distribution device and the runoff collected every 10 min for 30 min once the runoff started discharging from the plot. The volume of runoff, and percent reduction in concentration and mass of sediment [total dissolved solids (TSS)], phosphorus [dissolved reactive P (DRP), total P], nitrogen (total N), and bacteria (Escherichia coli, total coliforms) in runoff were determined. The findings did not support our hypothesis that percent reductions in concentrations and mass for sediment, nutrients, and bacteria were greater for mowed than unmowed buffers. In contrast, the findings supported our hypothesis that increasing buffer width would significantly (P≤0.05) decrease mass (but not concentration) of sediment, nutrients, and bacteria in runoff. The significant mass reduction was attributed to a reduced runoff ratio caused by longer residence time and greater infiltration in the wider buffers. Mass reductions for the three buffer widths ranged from 29 to 92% for TSS, 22 to 93% for DRP, 38 to 93% for total P, 23 to 92% for total N, and between 61 and 94% for E. coli and total coliforms. These findings suggest that buffer width but not mowing may reduce runoff quantity and improve runoff quality over the short term.