甜高粱在长江下游农区用作青贮作物的栽培利用技术研究

发布时间：2018-04-30 08:07

  本文选题：甜高粱 + 干物质产量　； 参考：《南京农业大学》2016年博士论文

【摘要】：农区种草是实现我国畜牧业现代化,促进粮食、经济、饲用作物三元种植结构协调发展的重要途径。长江下游农区地处亚热带,降水丰沛、热量充足,发展农区种草有很大的潜力。但这一地区是典型的“稻-经”二元种植模式地区,在饲草生产方面缺少适宜的品种和栽培技术。此外,该地区高温多雨,干草的加工调制受到限制,青贮成为保证全年粗饲料供应的重要手段。所以,筛选研究适于当地生态环境下种植的青贮饲料作物并研发配套的高产栽培利用技术,对长江下游农区种草养畜的持续发展有重要意义。甜高粱(Sorghum bicolor)为多用途C4植物,抗逆性强、适应性广、生物产量高、再生性好,是干旱地区的优良饲用作物。我国长江下游农区传统上将其作为嗜好作物零星种植。能否利用甜高粱抗逆和再生的优良特性,在潮湿多雨气候条件下用作青贮作物栽培利用?国内外少有报道。本研究以青贮玉米为参照,研究了甜高粱(cv.Hunnigreen)的干物质生产性能、营养价值、青贮品质和利用价值,论证了甜高粱在长江下游农区用作青贮作物的可行性。另外,通过系列的田间试验和实验室分析,研究了施氮水平和刈割次数对甜高粱生产性能、氮素利用率、光合作用、营养价值、青贮发酵品质和干物质体外瘤胃发酵特性的影响,提出了甜高梁在长江下游农区高产栽培和青贮利用的关键技术。主要研究结果如下:1.长江下游农区农田生态条件下,甜高粱的干物质(DM)、粗蛋白(CP)和可消化干物质产量远高于青贮玉米,分别为青贮玉米的1.54, 1.47和1.73倍。甜高粱的营养价值和青贮发酵品质与青贮玉米相当;青刈饲用及青贮品质的稳定性优于青贮玉米。甜高粱在长江下游农区用作青贮作物栽培利用潜力巨大。2.两年的施氮试验表明,长江下游农区甜高粱适宜的施氮量为200～400 kg N·hm-2,在该施氮范围内,DM产量高,氮素利用率高,氮素流失少。多元回归和通径分析表明,株高是决定DM产量的主要农艺性状,且不受施氮水平影响。茎叶比和叶面积指数对DM产量的影响在不同施氮水平下存在差异。施氮水平低于100 kg N·hm-2时,茎叶比对DM产量的直接作用最大(P=0.925),叶面积指数对DM产量的直接作用最小(P=0.162);施氮水平为200kgN·hm-2和300kgN·hm-2时,茎叶比对DM产量的影响降低(P=0.073 ),叶面积指数对DM产量的直接作用增加(P=0.797);而施氮水平为400 kg N·hm-2和500 kg N·hm-2时,茎叶比和叶面积指数对DM产量的直接作用均为负值(P=-0.125, P=-0.040)。这表明,高氮水平下的合理密植对甜高粱高产更为关键;而在较低施氮水平下,收获时间对饲草产量和品质的平衡作用更加突显。3.施氮水平和刈割次数对甜高粱光合作用有显著影响。叶片的净光合速率(Pn)随施氮量和刈割次数的增加而增加,在300 kg N·hm-2施氮水平,刈割3次处理下达最大值。叶片的表观量子效率(AQY),光饱和点(LSP)和羧化效率(CE)也均在刈割3次处理下达最大值,且显著高于其他处理组合。说明适当提高施氮量和增加刈割次数有利于提高甜高粱的光合能力。但是,高氮和高频刈割处理下暗呼吸速率(Rd)增大。因此,甜高粱干物质产量并没有与Pn同时在刈割3次处理下达到最大值,说明施氮水平与刈割次数的适当平衡,是提高甜高粱光合生产能力的关键。此外,随着生长期内刈割次数的增加,叶片硝酸还原酶活性(NRA)有增大的趋势。4.施氮水平和刈割次数对甜高粱饲草营养价值和青贮发酵品质有显著影响。结果表明,CP和可溶性碳水化合物(WSC )含量均随施氮量的增加而增加,分别在300 kg N·hm-2和225 kg N·hm-2处理下达最大值。两者对氮肥的不同响应,导致最终青贮发酵品质的不同。施氮量≥225 kg N·hm-2时,青贮甜高粱的pH值和乳酸含量无显著增加,丁酸和NH3-N含量均显著高于其他施氮处理。刈割2次处理下的CP含量最大,且有较高的WSC含量和适宜的含水量,因此在青贮过程中CP损失最小(9.7%),青贮后NH3-N含量最低,pH值低于刈割3次处理,费氏得分较高。虽然青贮后丁酸含量高于刈割3次处理,但两者无显著差异。因此刈割2次处理的甜高粱更适于青贮利用。5.干物质体外瘤胃消化特性的试验结果表明,增施氮肥对甜高粱饲草干物质降解率(DMD)无显著影响,但中性洗涤纤维降解率(NDFD)随施氮量的增加而降低。最大产气量在300 kg N·hm-2处理下达最大,但与150 kg N·hm-2和225 kg N·hm-2处理无显著差异。发酵产物中,除异丁酸(IBA)和异戊酸(IVA)外,总挥发性脂肪酸(TVFA)及其组分均随施氮量的增加而增加,在300 kg N·hm-2下达最大,但与225 kg N·hm-2处理无显著差异,乙酸/丙酸(A/P)在225 kg N·hm-2处理下达最大。(CO2/CH4(CCP)则随施氮量的增加而减小,说明增施氮肥虽然会增加CH4产量,但同时也有利于提高乙酸浓度。DMD和NDFD随刈割次数的增加而增大,但最大产气量却随刈割次数的增大而减小。发酵产物中除IBA外,TVFA及其组分均随刈割次数的增加而降低,但刈割2次处理下的AA和A/P均显著高于其他刈割处理,且CCP高于其他刈割处理。施氮处理对青贮饲料体外瘤胃发酵特性的影响与青贮原料基本一致,但刈割处理对青贮饲料体外瘤胃发酵特性的影响与青贮原料稍有不同。刈割2次处理下的青贮原料,其发酵产生的PA与其他刈割处理无显著差异,而青贮饲料发酵产生的PA显著低于其他别割处理,说明刈割2次处理的甜高粱青贮后,其瘤胃发酵类型更趋向于乙酸型。综合分析发酵酸和产气量,施氮量150 ～ 225 kgN·hm-2,全生长季内刈割2次处理下的甜高粱,更有利于瘤胃微生物的发酵。综上所述,甜高粱在长江下游农区可以用作青贮作物进行栽培利用,在其生长期内施氮225 kgN·hm-2,刈割2次可获得较高的生物产量和较好的饲草品质。
[Abstract]:Farming area grass planting is an important way to realize the modernization of animal husbandry in China and to promote the coordinated development of three yuan planting structure for grain, economy and forage crops. The lower reaches of the Yangtze River are located in subtropical zone, rich in precipitation and abundant in heat, and have great potential for developing agricultural grass planting. In addition, there is a lack of suitable varieties and cultivation techniques. In addition, the region has high temperature and rain, and the processing and modulation of hay are limited. Silage is an important means to ensure the supply of coarse feed for the whole year. Therefore, the selection of silage crops suitable for local ecological environment and the development of a matching high-yield cultivation and utilization technology are developed for the farmers in the lower reaches of the Yangtze River. The continuous development of planting grass and raising livestock is of great significance. The sweet sorghum (Sorghum bicolor) is a multipurpose C4 plant with strong resistance, wide adaptability, high biological yield and good regeneration. It is a fine feeding crop in arid areas. In this study, the dry matter production performance, nutritional value, silage quality and utilization value of sweet sorghum (cv.Hunnigreen) were studied with silage corn as reference. The feasibility of sweet sorghum used as a silage crop in the lower reaches of the Yangtze River was demonstrated. In addition, through a series of field experiments and laboratory analyses, the effects of nitrogen application level and cutting times on the production performance, nitrogen utilization rate, photosynthesis, nutrient value, silage fermentation quality and the fermentation characteristics of dry matter in vitro were studied. The key techniques for high yield cultivation and silage utilization of Sweet Sorghum in the lower reaches of Changjiang River were put forward. The main results are as follows: (1.) the dry matter (DM), crude protein (CP) and digestible dry matter yield of sweet sorghum are much higher than silage corn, 1.54, 1.47 and 1.73 times of silage corn, respectively. The stability is better than silage corn. The nitrogen application test of sweet sorghum used as a silage crop in the lower reaches of the Yangtze River for.2. for two years shows that the suitable nitrogen application amount of Sweet Sorghum in the lower reaches of the Yangtze River is 200~400 kg N. Hm-2. In the range of nitrogen application, the yield of DM is high, the utilization rate of nitrogen is high and the nitrogen loss is less. Plant height is the main agronomic character determining DM yield and is not affected by nitrogen application level. The effect of stem leaf ratio and leaf area index on DM yield is different at different nitrogen application levels. When nitrogen application level is lower than 100 kg N. Hm-2, the direct effect of stem and leaf ratio on DM yield is the most (P=0.925), and the direct effect of leaf area index on DM yield is minimal (P=0). .162); when the level of nitrogen application was 200kgN hm-2 and 300kgN. Hm-2, the effect of stem and leaf ratio on the yield of DM decreased (P=0.073), and the direct effect of leaf area index on DM yield increased (P=0.797), while the direct effect of stem leaf ratio and leaf area index on the yield of DM was negative when the nitrogen level was 400 kg N. The results showed that reasonable planting at high nitrogen level was more critical for high yield of sweet sorghum, while at low nitrogen level, the balance of harvest time on Yield and quality of forage forage showed that.3. nitrogen level and mowing times had significant effect on Photosynthesis of sweet sorghum. The net photosynthetic rate (Pn) of leaves increased with the increase of nitrogen application and mowing times. Addition, at 300 kg N hm-2 nitrogen application level, mowing 3 times the maximum value. The apparent quantum efficiency (AQY) of leaves, light saturation point (LSP) and carboxylation efficiency (CE) also reached the maximum value under the 3 treatment, and significantly higher than other treatment combinations. However, the dark respiration rate (Rd) increased under high nitrogen and high frequency mowing. Therefore, the dry matter yield of sweet sorghum did not reach the maximum value at the same time with Pn at the same time of cutting 3 times, indicating that the proper balance between the nitrogen level and the mowing times is the key to improve the photosynthetic capacity of the sweet sorghum. The nitrate reductase activity (NRA) increased, and the nitrogen level and cutting times of.4. had a significant effect on the nutritional value of sorghum forage and the quality of the silage fermentation. The results showed that the content of CP and soluble carbohydrate (WSC) increased with the increase of nitrogen application, and reached the maximum value at 300 kg N hm-2 and 225 kg N. Hm-2 respectively. The different response to nitrogen fertilizer resulted in the difference of the final silage fermentation quality. When the amount of nitrogen fertilizer was more than 225 kg N hm-2, the pH value and lactic acid content of the silage sweet sorghum were not significantly increased, and the content of butyric acid and NH3-N was significantly higher than that of other nitrogen treatments. The content of CP under the mowing treatment was the largest, and the content of WSC and the suitable water content were higher, therefore, the content of WSC and the appropriate water content were higher. In the process of silage, the loss of CP was the lowest (9.7%), the content of NH3-N was the lowest after silage, and the value of pH was lower than that of mowing 3 times. Although the content of Fermor was higher than that of 3 times of mowing, there was no significant difference between the two treatments. Therefore, the sweet sorghum which was mowing 2 times was more suitable for the experiment of the digestion characteristics of the rumen in the silage using.5. dry matter in vitro. There was no significant effect on the dry matter degradation rate (DMD) of the sweet sorghum forage, but the degradation rate of neutral detergent fiber (NDFD) decreased with the increase of nitrogen application. The maximum gas yield reached the maximum at 300 kg N. Hm-2 treatment, but no significant difference was found between the 150 kg N. Hm-2 and 225 kg N. Hm-2. The total volatile fatty acid (TVFA) and its components increased with the increase of nitrogen application, reaching the maximum at 300 kg N. Hm-2, but there was no significant difference from 225 kg N hm-2 treatment. Acetic acid / propionic acid (A/P) reached the maximum under 225 kg N. Hm-2 treatment. The concentration of.DMD and NDFD increased with the increase of mowing times, but the maximum gas yield decreased with the increase of mowing times. Except for IBA, the TVFA and its components decreased with the increase of mowing times, but the AA and A/P under 2 treatments were significantly higher than other mowing treatments, and CCP was higher than the other mowing. The effect of nitrogen treatment on the fermentation characteristics of silage in vitro was basically the same as that of silage, but the effect of Mowing on the rumen fermentation characteristics of the silage was slightly different from the silage material in vitro. There was no significant difference between the PA and the other mowing treatments of the 2 times of mowing, but the fermenting of the silage was fermented. The production of PA was significantly lower than other cutting treatments, indicating that the rumen fermentation type was more inclined to acetic acid after the 2 treatment of sweet sorghum silage. The fermentation acid and gas yield, the nitrogen application amount of 150~225 kgN. Hm-2, and the sweet sorghum under 2 treatments in the whole growing season were more beneficial to the fermentation of the rumen microorganism. Sorghum can be used as a silage crop for cultivation and utilization in the lower reaches of the Yangtze River, with 225 kgN hm-2 nitrogen applied during its growth period, and high biological yield and better forage quality can be obtained by cutting 2 times.

【学位授予单位】：南京农业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S54
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本文编号：1823758