牧区饲草储备量与牲畜出栏率的直线回归分析

饲草料储备量与牲畜出栏率之间存在着回归关系,建立回归方程;Y=-1.79 1.6x,预测和防止冬季牲畜缺草而形成的牲畜损失。     

杂交桑全草本栽培试验及其推广模式

经5年试验,山东省高密市杂交桑全年贴地伐条草本栽培获得圆满成功。试验区较通常的杂交桑留干收获法增产桑叶14．7％,5龄期收获桑叶用工节省43．2％,较品种选792桑园常规收获法增产桑叶29．9％,5龄期收获桑叶用工仅是选792桑园常规收获法的33．2％。推广模式：桑品种为桂桑优12或沙2×伦109;栽植形式为（90～100）cm×25cm;剪伐方式为每年的春、夏、秋3期蚕的4、5龄期用镰贴地伐条,实行条桑育。试验桑已种植7年,无衰败迹象。凡有水浇条件的地区,均可推广这种栽培与养蚕模式。     

Specific ion effect on the accumulation of abscisic acid in wheat

Studies were carried out in the glass house using sand culture to find out the specific ion effect on the accumulation of abscisic acid in wheat. Seeds were sown in sixteen different solutions of chloride, sulphate, nitrate, carbonate salts of sodium, potassium, calcium and magnesium used each at ‐2 bar osmotic potential. The leaf samples taken after 25 days of sowing indicated that osmotic as well as salt stress increased significantly the accumulation of abscisic acid. The accumulation of abscisic acid was significantly less under potassium and calcium salt ions as compared to that under sodium and magnesium salts ions. Overall effect of anions showed that accumulation of abscisic acid was more under PEG (osmotic stress and chloride salts but it was less under sulphate and nitrate salts and was the least under carbonate salts. The accumulation of abscisic acid was exceptionally high under potassium dihydrogen phosphate. In general, the accumulation of abscisic acid‐a growth inhibitor varied not only with the type of the cation but also depended on the accompanying anion indicating differential growth response of plants under different types of saline conditions having dominance of different salt ion(s).     

The influence of stocking rate and grazing system on the crude protein content and digestibility of Tarchonanthus veld in the northern cape 1

Abstract

Four stocking rates (10, 7, 6 and 4 ha/large stock unit), in both rotational and continuous grazing, have been applied with cattle on Tarchonanthus veld. The crude protein content and digestibility of organic matter of handcut samples and herbage samples collected by means of oesophageal fistulated steers in the different treatments, were determined.

The results indicated that the crude protein content (3,9 to 6,7%) and digestibility (48,7 to 59,4%) of handcut samples was not representative of the diet of grazing cattle. The crude protein content of the samples collected by means of oesophageal fistulated steers varied from an average of 13,6%. (October to December) to an average of 5,3% (July and August). On average, the digestibility of the fistula collected samples varied between 60,4% (February to April) and 50,2% (July to October). The crude protein content of the fistula collected samples tended to increase with increasing stocking rate while digestibility declined. Both crude protein content and digestibility of the fistula collected samples did not differ significantly between rotational and continuous grazing.     

Individual animal performance in relation to herbage mass and stocking rate in the Natal Sour Sandveld

Grazing trials were established at two sites in the Natal Sour Sandveld. The objective of this article was to present the patterns in individual animal performance in relation to herbage mass and stocking rate for the period November 1986 to September 1987. Rainfall exceeded the mean annual rainfall for Site 1 and was well below average for Site 2. Rainfall at Site 1 exceeded that at Site 2 by 329 mm. Distinct patterns in herbage mass were seen during the season. A grazing cut‐off was established at 2 000 kg/ha of herbage mass. Herbage mass seldom exceeded 2 400 kg/ha in grazed camps. A quantity limitation was evident for most of the growing season. The relationship between animal performance and stocking rate was linear but the slopes of the relationships differed.     

盐胁迫下不同水稻基因型根内Na^＋和Cl^—的分布情况比较

应用Ｘ－射线显微分析技术比较了基本性状相似。但耐盐性显著不同的３组共６个水稻基因型的根内Ｎａ＾＋和Ｃｌ＾－分布情况。在盐胁迫下，耐盐基因型根内中柱的Ｎａ＾＋含量称高于其它部位，而盐感基因型根中的Ｎａ＾＋则在整个横断面上分布得较为均匀，显示耐盐基因型根的中柱薄壁细胞对Ｎａ＾３＋有相对积累作用，从而控制Ｎａ＾＋向地上部的运转，Ｃｌ＾－在所有基因型的根横断面上分布都较为均匀。耐盐与盐敏感基因型之间没有明     

影响青海1号老芒麦产量的气候因子分析

[目的]为了明确影响青海老芒麦产量的关键气候因子,为青海老芒麦的大面积推广和应用提供理论依据。[方法]通过2000～2004年的田间试验,在抽穗至开花期测定2龄牧草的产量,通过点聚图与线性回归法分析青海老芒麦草产量与3个气候因子(降水、日照和温度)的相关性。[结果]在3个气候因子中,降水的变化趋势与青海老芒麦产量的变化趋势较为一致,呈极显著正相关(r=0.96),而日照和温度的变化对青海老芒麦产量的影响不显著。各月降水量的变异系数远高于气温和日照,说明与其它气候因子相比,降水是很不稳定的气候因子。降水量和牧草产量之间的回归方程为:Y=20792+3401.4 x。[结论]降水是影响青海老芒麦牧草产量的关键气候因子。     

Effects of species diversity on seasonal variation in herbage yield and nutritive value of seven binary grass-legume mixtures and pure grass under cutting

Intensively managed sown temperate grasslands are generally of low species diversity, although swards based on grass-legume mixtures may have superior productivity and herbage quality than grass-only swards. We conducted a cutting experiment over two years to test the effect of species composition and diversity on herbage yield, contents of N, neutral detergent fibre (NDF) and in vitro organic matter digestibility (IVOMD). Perennial ryegrass (PR, Lolium perenne) was sown alone and with each of four forage legumes: red clover (RC, Trifolium pratense), lucerne (LU, Medicago sativa), birdsfoot trefoil (BT, Lotus corniculatus) and white clover (WC, Trifolium repens); WC was also sown with hybrid ryegrass (HR, Lolium × boucheanum), meadow fescue (MF, Festuca pratensis) and timothy (TI, Phleum pratense). Herbage productivity was lowest in pure PR followed by PR/BT, and highest in PR/RC; this mixture had the highest legume proportion, N content and N yield. There was less WC in swards with HR and MF than with PR and TI. These differences were reflected in N contents of herbage of the mixtures. Legumes had higher N and lignin and lower NDF contents and IVOMD than grasses. Among legumes, NDF content was highest and IVOMD lowest in LU, followed by BT and the clovers. The highest N content was in WC. Among grasses, PR and HR had lower NDF contents and a higher IVOMD than MF; the highest N content was in PR. The grass component of mixtures had less effect than the legume component on herbage yield and quality. Results are discussed in terms of their potential to contribute to forage resources in farming practice and enhance resource use efficiency and ecosystem services.     

Pathways to improving the N efficiency of grazing bovines

Livestock production has been identified as a major source of nitrogen (N) losses. Therefore, it is important to reduce N output through animal excretions by improving N utilisation by the animal. The objective of this paper is to identify pathways for producing grass-based diets that maximise bovine N utilisation during grazing, based on literature on the interface of plant and animal sciences. The focus is on Western-European perennial ryegrass-based systems under rotational grazing and both beef and dairy production systems are considered.

Three pathways have been identified through which more efficient N utilisation by grazing bovines can be achieved by manipulation of the chemical composition of the grass forage: (1) matching protein supply to animal requirements, (2) balancing and synchronising carbohydrate and N supply in the rumen, and (3) increasing the proportion of rumen undegradable protein (RUP).

Matching the diet requirements of grazing bovines through herbage manipulation encompasses the manipulation of carbon (C) and nitrogen (N) contents of growing herbage. These C and N contents vary both spatially within the grass sward and over time. Under grazing conditions, grassland management tools, such as the length of the regrowth period, grazing intensity, fertiliser N application rate and herbage variety are the main pathways to manipulate C and N dynamics. Regrowth length, N application rate and high sugar varieties were shown to be the most promising grassland management tools with respect to manipulating herbage quality and subsequent bovine N efficiency. However, these management tools are interrelated and may show adverse effects on production.

Due to the complex nature of interactions, modelling is essential in order to quantify and predict the effect of any combination of herbage management tools under specific circumstances.

Areas in which additional research is required are the fractionation of N compounds in herbage as affected by herbage management, and the effect of high sugar varieties on bovine N efficiency under a range of herbage management combinations.