Physical, fermentative, and nutritional quality of silages made from three Sorghum bicolor varieties as affected by ensiling duration in South-west Nigeria.

Despite large-scale sorghum production in Nigeria, its utilization as livestock feed is limited to the stover following grain harvest. Therefore, we evaluated the physical, fermentative, and nutritive quality of whole-crop silages from three Sorghum bicolor varieties at different ensiling durations. The experiment was 3×5 factorial comprising three varieties (Samsorg14, Samsorg17, and Samsorg41) and five ensiling durations (0, 4, 8, 12, and 16 weeks). Forages were ensiled at the dough stage, and the silos were opened at the pre-determined durations for quality analyses. Samsorg14 silage recorded higher pH (5.88) and significant titratable acidity (8.32 g kg-1), while the least pH was observed for Samsorg17 silage (4.63). The forages ensiled for 8 weeks had a higher pH (5.04) compared with 4.51, 5.03, and 4.57 recorded at 4, 12, and 16 weeks, respectively. In contrast, forages ensiled for 4 weeks recorded the highest titratable acidity (8.39) and Flieg point (104.07). CP content was higher in fresh Samsorg17 (110.64 g kg-1) and lower (71.01 g kg-1) in Samsorg41 ensiled for 8 weeks as influenced by variety × ensiling duration. Cumulative gas volume and methane were higher for Samsorg41 silage (21.21 and 6.76 ml 200 mg-1 DM respectively). Ensiling for 16 weeks resulted in higher silages' IVDMD (44.00%) compared with other ensiling durations. Samsorg14 and Samsorg17 had a relatively stable silage pH, higher CP, and digestibility. Therefore, their silages could be conserved up to 16 weeks to provide high-quality feed for ruminants during the dry season to maintain animal productivity and ultimately enhance food security.

Different responses of plant N and P resorption to overgrazing in three dominant species in a typical steppe of Inner Mongolia, China.

Nutrient resorption from senesced leaves is an important mechanism for nutrient conservation in plants. However, little is known about the effect of grazing on plant nutrient resorption from senesced leaves, especially in semiarid ecosystems. Here, we evaluated the effects of grazing on N and P resorption in the three most dominant grass species in a typical steppe in northern China. We identified the key pathways of grazing-induced effects on N and P resorption efficiency. Grazing increased N and P concentrations in the green leaves of Leymus chinensis and Stipa grandis but not in Cleistogenes squarossa. Both L. chinensis and S. grandis exhibited an increasing trend of leaf N resorption, whereas C. squarrosa recorded a decline in both leaf N and P resorption efficiency under grazing. Structural equation models showed that grazing is the primary driver of the changes in N resorption efficiency of the three dominant grass species. For L. chinensis, the P concentration in green and senesced leaves increased the P resorption efficiency, whereas the senesced leaf P concentration played an important role in the P resorption efficiency of C. squarrosa. Grazing directly drove the change in P resorption efficiency of S. grandis. Our results suggest that large variations in nutrient resorption patterns among plant species depend on leaf nutritional status and nutrient-use strategies under overgrazing, and indicate that overgrazing may have indirect effects on plant-mediated nutrient cycling via inducing shifts in the dominance of the three plant species.

Overgrazing-induced legacy effects may permit Leymus chinensis to cope with herbivory.

There is growing evidence that herbivory-induced legacy effects permit plants to cope with herbivory. However, herbivory-induced defense strategies in plants against grazing mammals have received little attention. To further understand the grazing-induced legacy effects on plants, we conducted a greenhouse experiment with Leymus chinensis experiencing different grazing histories. We focused on grazing-induced legacy effects on above-ground spatial avoidance and below-ground biomass allocation. Our results showed that L. chinensis collected from the continuous overgrazing plot (OG) exhibited higher performance under simulated grazing in terms of growth, cloning and colonizing ability than those collected from the 35-year no-grazing plot (NG). The enhanced adaptability of OG was attributed to increased above-ground spatial avoidance, which was mediated by larger leaf angle and shorter height (reduced vertical height and increased leaf angle contributed to the above-ground spatial avoidance at a lower herbivory stubble height, while reduced tiller natural height contributed to above-ground spatial avoidance at a higher herbivory stubble height). Contrary to our prediction, OG pre-allocated less biomass to the rhizome, which does not benefit the herbivory tolerance and avoidance of L. chinensis; however, this also may reflect a tolerance strategy where reduced allocation to rhizomes is associated with increased production of ramets.

Stoichiometric ratios support plant adaption to grazing moderated by soil nutrients and root enzymes.

BACKGROUND: Vegetation succession is one of the major driving processes of grassland degradation. Stoichiometry significantly contributes to vegetation dynamics. However, a knowledge gap exists in how soil nutrients and root enzymes influence the stoichiometric ratio to affect vegetation dynamics. METHODS: To address these questions, we selected a dominant species (Leymus chinensis (Trin.) Tzvel.) and a degraded-dominant species (Artemisia frigida Willd.) under different management regimes (enclosure and grazing) on the Inner Mongolia steppe. We measured (i) plant nutrient concentrations, (ii) root enzymes and (iii) soil nutrients to investigate how the selected plant species responded to grazing. RESULTS: The results show that: (i) N and P concentrations and the C:N:P ratio in different organs are significantly affected by grazing, and there is variation in the plant species' response. Grazing significantly increased N and P in the leaves and stems of L. chinensis and the stems and roots of A. frigida. (ii) Grazing significantly increased the activities of glutamine synthase but decreased the activities of acid phosphatase in L. chinensis. The nitrate reductase and acid phosphatase activities significantly increased in A. frigida under grazing conditions. (iii) Grazing decreased the total nitrogen, total phosphorus, and available nitrogen, but increased the available phosphorus in the soil. CONCLUSION: We conclude that A. frigida is better adapted to grazing than L. chinensis, possibly because of its relatively increased stem and root growth, which enhance population expansion following grazing. Conversely, L. chinensis showed increased leaf and stem growth, but suffered nutrient and biomass loss as a result of excessive foraging by livestock, which severely affected its ability to colonize. Root enzymes coupled with soil nutrients can regulate plant nutrients and stoichiometric ratios as an adaptive response to grazing. Thus, we demonstrated that stoichiometric ratios allow species to better withstand grazing disturbances. This study provides a new understanding of the mechanisms involved in grazing-resistance within a plant-soil system.