Does harvesting cover crops eliminate the benefits of cover crops? Insights after three years
2021
Blanco‐Canqui, Humberto | Drewnoski, Mary E. | Rice, Dan (Daniel G.)
Harvesting cover crops (CCs) can provide economic benefits, but its impacts on soils and crop yields are little known. We studied the 3‐yr cumulative impacts of CC harvest on soil compaction, water and wind erosion potential, water infiltration, fertility, and crop yields under irrigated no‐till continuous corn (Zea mays L.) silage in southeastern Nebraska. Treatments were: (a) no CC, (b) non‐harvested multspecies CC mix, and (c) harvested CC mix (10‐cm cutting height). Compared with non‐harvested CC, harvested CCs did not affect bulk density or penetration resistance, indicating that it did not increase soil compaction risks. Similarly, it did not affect wet aggregate stability. Harvested CCs, however, reduced total cumulative infiltration by 63% (27.7 vs. 10.33 cm), organic matter concentration by 9% (44 vs. 40 g kg–¹), and dry aggregate size by 21% (1.58 vs. 1.25 mm), relative to non‐harvested CCs, suggesting that harvesting CCs may reduce CC benefits of water capture and wind erosion control. Compared with no CCs, harvested CCs reduced wind‐erodible fraction by 36% (0.58 vs. 0.37) and nitrate concentration by 37% (81 vs. 51 mg kg–¹), and increased dry aggregate size by 38% (0.77 vs 1.25 mm). These results suggest that harvested CCs can still provide benefits for reducing wind erosion and nitrate leaching potential relative to not planting CCs. Harvested CCs did not reduce corn silage yield in two of three years. Overall, harvesting CCs did not reduce all the soil benefits, but long‐term (>3 yr) monitoring is needed to fully understand CC harvest impacts.
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