PARENT SESSION
Contributed Oral Session 109: Agroecology: Soils; Nutrient Cycling
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 513 A, Level 5, Palais des congrès de Montréal
Diversifying cover crop systems in California conservation tillage rotations: Tightening the N cycle and increasing agroecosystem function.
Koffler, Kaden*,1, Six, Johan 1, van kessel, Chris1, Kaffka, Steve1, Temple, Steve 1, 1 University of California-Davis, Davis, CA, USA
ABSTRACT- Cover crops can improve agroecosystem performance by enhancing N cycling, but little information exists on optimizing cover crop potential in crop rotations. We hypothesized that a diversified cover crop system in a California tomato-corn conservation tillage rotation would improve synchrony between N availability and corn N demands, thereby enhancing agroecosystem function. The two cover crop treatments were 1) winter legume cover crop (WCC) and 2) diversified system with both summer cover crop legume/grass mixture and winter legume cover crop (SCC+WCC). Biomass production was measured and cover crops were labeled with 15N to determine N fixation, N turnover, and cover crop derived corn grain N content. More cover crop biomass was produced (p<0.01) in SCC+WCC than WCC (7778±213 and 6167±254 kg ha-1, respectively), but there was no difference in total N production between the two (291±23 and 258±19 kg ha-1, respectively). Total N-fixation was more than two times higher (p<0.02) in SCC+WCC than WCC (193±21 and 83±30 kg ha-1, respectively), which suggests summer cover crop soil N uptake drew down available soil N pools, forcing more winter cover crop N fixation. Corn yields of WCC and SCC+WCC were not statistically different (9445±554 and 11131±1448 kg ha-1, respectively), however, corn grain N content was significantly higher (p<0.01) in SCC+WCC than in WCC (160±21 kg ha-1 and 113±9 kg ha-1, respectively). The amount of corn grain N derived from cover crops was not statistically different between WCC and SCC+WCC (25.2±2.0 and 34.2±6.8 kg ha-1, respectively), but the amount of corn grain N derived from cover crop fixation was nearly three times higher (p<0.05) in SCC+WCC than in WCC (23±4 and 8±3 kg ha-1, respectively). Our results support the hypothesis that structurally and temporally diversified cover crop systems can increase agroecosystem functioning by tightening N cycling with improved synchrony between N inputs from fixation, available soil N pools, and corn grain N uptake.
Key words: cover crop, agroecosystem function, diversity, N cycle