Rice straw and sweet potato vines are the main by-products of agricultural crops, and their disposal creates problems for the environment in the south of China. In order to establish an easy method for making rice straw silage successfully, experiments were conduct to evaluate fermentation quality and nutritive value of rice straw silages ensiled with or without sweet potato vine. Paddy rice straw (PR) and upland rice straw (UP) were ensiled alone or with sweet potato vines (SP) by a ratio of 1:1 (fresh matter basis), over 3 years. Compared with rice straw silages ensiled alone, the mixed-material silages (PR + SP, UR + SP) showed higher fermentation quality with lower propionic acid content and NH -N ratio of total N, and higher (P < 0.05) concentrations of lactic acid and acetic acid, resulting in decrease (P < 0.05) of dry matter loss and higher (P < 0.05) in vitro ruminal dry matter digestion. When the fermentation quality, chemical composition and in vitro rumen fermentation characteristics were considered, ensiling would be an effective way of utilization of rice straw and sweet potato vines in the regions where rice and sweet potato are harvested at same season, and the sweet potato vines have the potential to improve rice straw fermentation quality with low water soluble carbohydrate content in south of China.

In order to better utilize the last cut alfalfa harvested before killing frost in a high moisture environment, the effects of chemical additives on the quality of alfalfa silage were studied in south of China. The alfalfa was freshly harvested at branching stage, and wilted by dry matter content of about 300 g/kg (fresh matter basis). Silage was prepared by using a small-scale silage fermentation system, where sucrose, potassium citrate, sodium carbonate, formic acid, acetic acid and propionic acid were used as silage additives, and no additives served as control. These silos were stored at ambient temperature (5-20°C), and the silage qualities were analyzed after 120 days of fermentation. All additive treatments affected the chemical composition and N distribution, increased the water-soluble content and crude protein contents, decreased non-protein nitrogen (NPN) content, and enhanced the in vitro ruminal dry matter digestibility (except for sodium carbonate). Silages treated with organic acids were preserved with significantly (P < 0.05) lower pH value, ethanol content and NPN content compared with control. When the fermentation quality, chemical composition and N distribution were considered, the treatment with sucrose or organic acids resulted in high quality of alfalfa silage ensiled before killing frost, with formic acid having the best effect.

Key determinants of regrowth rate following harvest in alfalfa (Medicago sativa L.) are the levels of root carbon (C) and nitrogen (N) reserves. This study was undertaken to assess the impact of alfalfa cultivars differing in fall dormancy on regrowth potential in relation to the quantitative changes in root C and N reserves at the onset of regrowth. Five contrasting alfalfa cultivars were grown in the field and were harvested three times. Shoot regrowth dry weight increased significantly with decreasing fall dormancy. Alfalfa cultivars with less dormancy tended to have higher concentrations of root C and N reserves, whereas significantly greater pools of root C and N reserves were found in roots at each harvest time because of greater root dry weight. Shoot regrowth was positively correlated to the pools of root soluble sugar, starch and total non‐structural carbohydrates, but not correlated to their concentrations at each harvest time. Shoot regrowth was also linearly related to the pools of root total N and soluble proteins, but not consistently related to their concentrations. Our results suggest that the total amount of C and N organic reserves in alfalfa roots rather than their concentrations are determining factors of shoot regrowth.

No abstract

Non‐dormant alfalfa (Medicago sativa L.) has been cultivated successfully in the east central regions of China as a short‐term component of a forage‐grain rotation system, but it remains unclear how shoots of alfalfa with different levels of fall dormancy develop in this system. Five alfalfa cultivars with contrasting fall dormancy were sown in the field in Nanjing, China, in October 2012 and 2013, and were harvested three times in the following year. The number and dry weight of shoots that originated from crown (crown shoots) and axillary buds (axial shoots) were recorded at each harvest. The results were analyzed for dormant, semi‐dormant and non‐dormant cultivars over 2 years. At the first spring harvest, axial shoots accounted for an average of 18.3% of dry weight per plant and became the dominant shoot type during later harvests. Crown shoots accounted for 81.7% of plant dry weight in first harvest and the majority of dry weight per plant totaled over three harvests in all fall dormancy types. Fall dormancy had little effect on the relative proportion of crown and axial shoots in dry weight per plant, and the number of crown and axial shoots. Non‐dormant cultivars produced heavier individual crown and axial shoots, resulting in greater dry weight per plant at each harvest. Our results show that non‐dormant cultivars used in our study produce greater dry weight per plant under a short‐term cultivation system, primarily because they have greater dry weight of individual crown and axial shoots.