Effect of urea fertilization on biomass yield, chemical composition,in vitrorumen digestibility and fermentation characteristics of straw of highland barley planted in Tibet

Abstract

SUMMARYA completely randomized experiment for planting highland barley in 36 field plots of the Lhasa Agricultural Experiment Station was applied to investigate the effect of urea nitrogen (N) fertilization levels of 0 (control), 156, 258, 363, 465 and 570 kg/ha on nutrient accumulation, in vitro rumen gas production and fermentation characteristics of highland barley straw (HBS). Each urea application was divided into three portions of 0.4, 0.3 and 0.3 and sequentially fertilized at seeding (growth stage (GS) 0), stem elongation (GS 32) and heading (GS 49), respectively. The maturity stage lasted 5-13 days longer in response to the urea N fertilization compared with the control. After removing grains, HBS biomass was harvested at maturity. The biomass yields of leaf, stem, straw and grain were increased quadratically with increasing urea N fertilization, and HBS and grain yields peaked at the estimated urea N fertilization levels of 385 and 428 kg/ha, respectively. The increase of urea N fertilization increased the accumulation of crude protein, cellulose and lignin, and decreased the content of ash and hemicellulose in HBS, resulting in a decrease of the energy content available to be metabolized. After incubating HBS for 72 h with rumen fluids from lactating cows, the urea N fertilization decreased in vitro dry matter disappearance and cumulative gas production, and slightly altered fermentation end-gas composition. Urea N fertilization decreased microbial volatile fatty acid production, but did not alter the ratio of lipogenic acetate and butyrate to glucogenic propionate. In a brief, the current urea N fertilization strategy promoted the growth of the highland barley and increased biomass yield, protein and cellulose accumulation of HBS. A urea N fertilization level ⩽385 kg/ha could be sufficient for growth of highland barley in Tibet without a consequent nutritive reduction in ruminal digestion.

Silage Fermentation and In Vitro Degradation Characteristics of Orchardgrass and Alfalfa Intercrop Mixtures as Influenced by Forage Ratios and Nitrogen Fertilizing Levels

“…The concentrations of branched-chain VFAs produced were mainly dependent on the composition and extent of ruminal deamination of amino acids in feeds, and higher CP was significantly correlated with the higher molar concentrations of valerate and isovalerate production [65], which explained the higher ruminal valerate and isovalerate production with increasing alfalfa proportion in the present study. However, no effects of N levels occurred on the molar concentrations of branched-chain VFAs in the present study because the community of dominant ruminal microbes and fermentation pathways of VFA end-products were not affected or changed [19].…”

“…The entire content of each bottle was filtered with pre-weighed nylon bags (8 × 12 cm, 42 µm pore size) to obtain the non-degraded particles. Ten milliliters of filtrate were sampled to measure the concentrations of ammonia N and volatile fatty acids (VFAs) [19]. The nylon bags were then thoroughly rinsed with fresh water and then oven-dried at 65 • C for 48 h. The in vitro dry matter disappearance (IVDMD), in vitro neutral detergent fiber disappearance (NDFD), and in vitro acid detergent fiber disappearance (ADFD) was calculated by the difference between the pre-incubated and post-incubated amounts, corrected by the blanks after the incubation.…”

Rhizosphere Bacterial Community Response to Continuous Cropping of Tibetan Barley

“…The ability of the rhizosphere soil to transform nitrogen elements decreases during continuous cropping, and the decreased TN and AN may attribute to the low yields of Tibetan barley in the fields. The grain yields of Tibetan barley ranged from 1.5 to 6.1 t ha −2 with different concentrations of urea N fertilization (Cui et al, 2016). According to the Standard of Qinghai Province (DB63/T1536-2020), the high, intermediate, or low yields of Tibetan barley are 5.25 to 6.00 t ha −2 , 4.50 to 5.25 t ha −2 , and 4.05 to 4.5 t ha −2 , respectively.…”

Combining Orchardgrass and Alfalfa: Effects of Forage Ratios on In Vitro Rumen Degradation and Fermentation Characteristics of Silage Compared with Hay

“…For each cultured fluid, the concentrations of ammonia N [23] and MCP [24] were determined. The determination of VFAs was conducted according to the method described by Cui et al [25]. Briefly, the filtrate of each cultured fluid kept in polypropylene tubes (10 mL) was centrifuged at 3500× g for 15 min at 4 • C and 1.0 mL of the supernatant sample was mixed with 0.3 mL of 250 g/L orthophosphoric acid solution into a polypropylene microtube for 30 min.…”

“…Thereafter, the mixture was cooled at 4 • C for 2 h and centrifuged at 15,000× g for 10 min at 4 • C. The supernatants were kept at −20 • C for later VFAs analysis. Methane, CO 2 , and hydrogen gas (H 2 ) produced per kg OM digested were measured with a gas chromatograph according to the method described by Cui et al [25].…”