Herbage production, botanical and plant-part composition of mixed black oat (Avena strigosa Scherb.) annual ryegrass (Lolium multiflorum Lam.) pastures under different management strategies

Abstract

Mixing annual ryegrass and black oat can improve forage production in subtropical and temperate areas with integrated crop-livestock systems. Thus, we evaluated the forage production dynamics of mixed annual ryegrass-black oat pastures under different management strategies based on canopy height and supplement level. Pastures were continuously stocked with Boer goats at two grazing heights (12 or 21 cm); animals received or did not receive energy supplements (0 and 15 g kg-1 of body weight). These treatments were applied using a factorial scheme (2 × 2) and randomized block design with three replications. We evaluated the herbage accumulation rate (kg of DM h-1 day-1) using the exclusion cage technique, herbage mass (HM, kg of DM ha-1) using the double sampling technique, and botanical and plant-part composition (%) of destructive samplings. Supplementation had no effect on the parameters measured (P ≤ 0.05). Annual ryegrass become the predominant species during the experimental period and mainly at the lowest canopy height. Total herbage production during the 131 days of pasture utilization was 10,280 kg of DM ha-1. The herbage accumulation rate was similar between the two canopy heights; however, it varied throughout experimental period. Leaf lamina mass was lower in treatments 12 cm up to 102 after sowing; after that, they were equivalent. At the end of the study, herbage mass was 2720 kg DM ha-1 with the 21-cm treatment and 2170 kg DM ha-1 with the 12-cm treatment. It is recommended to maintain mixed annual ryegrass-black oat pastures at 12 cm in height. Reasons are discussed throughout the text.

Grazing intensity and nitrogen fertilization effects on biomass and morphology of black oat roots in an integrated crop–livestock system

“…The experimental treatments consisted of three grazing intensities of the black oat pasture (1) heavy grazing, (2) moderate grazing, and (3) ungrazed (control). Moderate grazing had a post‐grazing stubble height of 15 cm (Carvalho et al., 2018; Savian et al., 2014; Soares et al., 2019), while heavy grazing had a post‐grazing stubble height of 7 cm (Assmann et al., 2015; Carvalho et al., 2018; Ribeiro, Dieckow, et al., 2020). Grazing intensities were combined with three topdressing N rates of 0, 75, and 150 kg N ha −1 , applied in the form of urea.…”

“…In this region, heavy grazing is characterized by low forage allowance and residual stubble height below 10 cm (Assmann et al., 2015; Carvalho et al., 2018; Ribeiro, Dieckow, et al., 2020), which compromises pasture production and root growth (Piazzetta et al., 2014; Ribeiro, Dieckow, et al., 2020), reducing the overall system productivity (Carvalho et al., 2010; Kunrath et al., 2020). Conversely, moderate grazing of black oat is characterized as a residual stubble height of 15–20 cm (Carvalho et al., 2018; Savian et al., 2014; Soares et al., 2019). In ICLS, moderate grazing has been reported to not affect root growth negatively and has been recommended as a practice to maintain soil C stock (Ribeiro, Ibarr, et al., 2020, 2021) and pasture productivity (Carvalho et al., 2010; Kunrath et al., 2020).…”

FORAGE YIELD, ELONGATION RATE AND BOTANICAL COMPOSITION OF Lolium multiflorum LAMB. IN RESPONSE TO DIFFERENT GRAZING INTERVALS AND INTEN

“…Bribiesca et al (2002) observed leaf to stem ratios of 1.4 and 1.1 in a perennial ryegrass pasture harvested at a plant height of 3 and 15 cm, respectively. Plant age affects yield of plant morphological components (Soares et al, 2019;Beecher et al, 2015;Hopkins et al, 2006).. As plants age with increasing grazing interval, leaf production drops and the proportion of both stem and senescent material increases or negatively affecting leaf to stem ratio (Soares et al, 2019;Beecher et al, 2015;Hopkins et al, 2006). Results in the present study are consistent with previous studies in that plant height increased with increasing GIv (Barthram and Grant, 1984;Hurley et al, 2013).…”