2017-144: Development of best management practices for residue and fertility management of annual polyculture
Researcher: Jillian Bainard
Reducing inputs and increasing soil health provides a win-win scenario for producers. Annual polycrop mixtures could more closely mimic the natural ecosystem, which is thought to reduce inputs, improve soil, suppress weeds, increase yield, increase C sequestrations, etc. This study will investigate the effect of annual polyculture residue and fertility management on forage production/quality, soil health, & productivity. Three different polycrop mixtures suitable for each region, rotated with cereal crops, will be evaluated in field trials at Melfort and Swift Current
The purpose of this study was to develop best management practices for the incorporation of diverse annual forage crop mixtures (polycultures) into cropping rotations, to note the annual polycrop residue, nitrogen fertility, soil health, and production productivity. Three diverse annual forage mixtures were used: a "balanced mix" (equal proportions of oats, barley, peas, hairy vetch, Groundhog Radish, and Hunter hybrid brassica), a "nitrogen fixing mix" (peas, hairy vetch, Berseem clover), and a "weed control mix" (oats, peas Groundhog radish, Hunter hybrid brassica, Winfred hybrid brassica). They were grown under three fertilizer rates and with three residue amounts.
During the 2018 growing season, near Swift Current, Saskatchewan, the balanced mix produced the produced the highest biomass, and the balanced and weed control mixes performed similarly for weed control while the N-fixing mix had the most weeds. Forage quality was similar between the mixtures but the higher inclusion of legumes resulted in lower fiber and increased protein.
Prior to seeding in spring 2019, soil moisture was highest under 100% residue for all cropping treatments, showing some bene to having the ground covered through the fall and winter. Spring soil nitrous oxide was significantly greater under the treatments that received more fertilizer and residue.
In spring 2019, a wheat monoculture was seeded over all plots, and there were significant effects of the previous treatments on the productivity of the wheat crop. Higher wheat yields were found with higher fertilizer and residue rates. Following the wheat harvest, the researchers, they could still observe impacts of the 2018 crop on the soil, particularly as the N-fixing plots had higher soil moisture, higher nitrogen, nitrate, and organic carbon.
In 2020, a pea monoculture was seeded over all the plots. Pea yield was lowest on the N fixing plots, indicating concerns with seeding legumes too soon after a polyculture that includes a high proportion of legumes, likely due to pathogen buildup.
Interestingly, in 2020 the weeds were highest in the plots that had the most weeds in 2018 even though this effect was not observed in 2019. These impacts on the weed seed bank became evident once a less competitive crop was grown (peas vs. wheat). In fall 2020, following the second annual crop rotation of a pea crop, no soil factors were significant any longer, suggesting that the soil nutrient dynamics following a forage polyculture might be short-lived in a semi-arid system of Swift Current.
For a video presentation on this project, please visit: https://www.youtube.com/watch?v=NPUhDFjQI2A