Effects of crop rotation and sheep grazing management on the seedbank and emerged weed flora under a no-tillage integrated crop-livestock system

Abstract

Effective integrated weed management in agricultural landscapes depends on the ability to identify and manage processes that drive weed dynamics. The current study reports the effects of grazing management and crop rotation strategies on the seedbank and emerged weed flora in an integrated crop-livestock system (ICLS) experiment during a 12-year period under no-tillage in sub-tropical southern Brazil. During winter, Italian ryegrass cover crops were grazed by sheep: grazing management treatments included two stocking methods (continuous and rotational) and two forage allowances (10 and 20 kg of herbage dry matter available per 100 kg animal live weight). During summer, the crop rotation treatments involved either soybean-maize or soybean-soybean in succession with winter-grazed cover crops. The treatments were part of a factorial randomized complete block design. Treatment effects were evaluated on the weed seedbank and emerged weed flora populations during winter-grazed cover crop and summer crop growth as well as during the harvest phase. The current results demonstrate that crop rotation and grazing management exhibited interactive effects on the determination of weed outcomes in an ICLS. However, overall, compared with moderate forage allowance, high forage allowance during the winter-grazed cover crop caused lower emerged weed flora in subsequent crops (20% reduction during crop growth and 90% reduction at crop harvest) and 48% reduction in seedbank size. High forage allowance promoted more residue from winter-grazed cover crop biomass, which remained during the summer crop phases and probably resulted in a physical barrier to weed emergence.

Plant community responses to integrating livestock into a reduced‐till organic cropping system

“…Research on integration of livestock into cropping systems has produced a wide range of weed community responses (Tracy and Davis 2009, Hilimire 2011, McKenzie et al 2016, Schuster et al 2018, MacLaren et al 2019, Rosa‐Schleich et al 2019). These discrepancies stem from differences in duration of study, and location and system studied.…”

Optimizing forage allowance for productivity and weed management in integrated crop-livestock systems

“…No random effects of fields or farmers were observed for this relationship. Schuster et al (2018) showed the importance of straw in reducing weed emergence, which may explain why weed emergence decreased exponentially as the sward height increased (Fig. 2a).…”

“…Nevertheless, cover crops with high dry matter production and forage potential can also provide a source of grazing for livestock and thus provide an additional source of revenue for farmers and increase food production per unit area between successive grain crops (Moraes et al 2014;Nie et al 2016;Sulc and Franzluebbers 2014). However, many reports indicated that some of the benefits provided by cover crops depend on the amount of residue left on the surface (Webster et al 2016;Schuster et al 2018) and grazing of cover crops may have a direct impact on the residual straw amount (Hunt et al 2016). There is still a lack of information about the minimum sward height of winter grazed cover crops that does not negatively affect weed control benefits, as well as the sward height that promotes high meat production with the best combination of stoking rates and animal performance (Fig.…”

Reintegration of Crop-Livestock Systems in Europe: An Overview

“…In Brazil, a soybean-beef cattle rotation found that high grazing intensity (sward maintained to < 10 cm) increased the weed seed bank by more than threefold, whereas low grazing intensity (sward maintained to 30-40 cm) decreased the seed bank by 42% [102] . This was attributed to the taller sward outcompeting weeds.…”