施氮量对春小麦根系生长及产量的影响

为探讨施氮量对春小麦根系生长及产量的影响,选用龙麦26和龙麦33为试验材料,分析了不同施氮水平(45、60、75、90和105 kg·hm-2)下春小麦根系性状和籽粒产量的差异.结果表明,施氮量对春小麦根系生长有影响,但在不同根系性状上表现不同.随着施氮量的增加,根系总长、干重、活力呈先升后降趋势,根面积和体积呈升高趋势,根平均直径和根冠比呈下降趋势.春小麦产量也显著受施氮影响,并随施氮量的增加呈先升后降趋势.两个品种均在75～90 kg·hm-2施氮量下获得较好的根系生长状况和增产效果.说明合理施氮可通过促进春小麦根系生长而提高籽粒产量.     

Effect of the Interaction between Cultural Condition and Genotype on Spike Morphogenesis in Spring Wheat

Abstract

The number of grains per spikelet and the number of spikelets per spike are important factors that influence grain yield in wheat. Three wheat genotypes in four foreign groups (OA, OC, OH and OJ) differing in spike type and Japanese cultivars (cvs) were grown under various combinations of seeding densities and fertilization levels. In all groups, the spikelet number per spike and the spike length at maturity were highest at low seeding densities and high levels of fertilization. The OA group (Nepal) and Haruyutaka (Japanese cv) gave a weak response in spikelet number per spike, while the OJ group (Xinjiang Uygur, China) gave a weak response in spike length. The OC group (except for T6), the OH group (Tibet) and Japanese cvs (except for Haruyutaka) responded to treatments in both spikelet number per spike and spike length. The T6 genotype in the OC group (Nepal) gave a weak response in both spikelet number per spike and spike length. Although the OA group had the longest spikes and the OJ group had the shortest spikes, there was no difference in the duration of spike elongation between the OA group and the OJ group. Spike length appeared to be determined mainly by the rate of spike elongation and was not restricted by the dry weight of the spike during the growth phase of the spike.     

Factors Relating to Seedling Emergence in Spring Wheat

Abstract

Spring wheat (Triticum aestivum L.) is cultivated in the northern part of Japan. Although the vigorous early growth of spring wheat is desirable, the rapid and uniform emergence of seedlings is reduced by adverse environmental effects, such as excessive soil moisture and low temperature. Analyses of correlations between field emergence day and germination traits under low temperature, after treatment with polyethelene glycol (PEG) and after flooding treatment of 44 varieties from Japan and other countries indicated a general absence of interrelationships. Moreover, there was no significant correlation between field emergence days in trials in 1996 and 1997. Small and large seeds of Haruyutaka harvested in 1994 and 1996 were hand-sown at depths of 3 cm and 10 cm without fertilizer and with standard fertilizer in brown forest soil in a field of the Tokyo University of Agriculture in Hokkaido. The superiority of large seeds over small seeds was demonstrated by the production of more shoot dry matter with sowing at a depth of 3 cm and by the number of emerged plants with sowing at a depth of 10 cm. Although the coefficients of correlation between field emergence day and germination traits of the wheat varieties were low, a sowing method that optimized seedling growth in the field was demonstrated in this experiment.     

Seasonal diet composition and forage selectivity of Boer goats in a semi-arid gypsophilous grassland

Botanical and chemical compositions of Boer goat diets, determined with repeated collection of forage samples taken from the goat’s mouth, were studied in a gypsophilous grassland during four seasons of the year. Ten pluriparous goats were used to collect selected forage species. Shrubs were a minor dietary component throughout the year (<7.5%). Goats selected more (p?<?0.01) grass during autumn and winter (34.2–37.8%) than during spring (21.2%) and summer (29.0%). During all seasons goat diets were dominated by forbs (>59%). Diets were lowest (p?<?0.05) in percentage of crude protein during spring, summer and autumn (13.2?±?3.5, 13.2?±?2.4 and 14.2?±?3.9, respectively) than winter (17.5?±?2.9) with levels above the recommended quantities for goats throughout the year. In vitro dry matter digestibility of forages selected by goats did not differ between seasons (range 47.4–53.3%). It was concluded that in this particular ecosystem goats preferred forb species over grasses across all seasons. In addition, goats maintained relatively stable diet quality by forage-class mixing of diets.     

“n Voorlopige evaluasie van eenjarige,wintergroen weidings met speenlammers,in die Oos‐Kaapse suurveld

A preliminary evaluation of annual, wintergreen pastures using weaned lambs in the eastern Cape sourveld. Animal production and feed availability on oats, vetch and oats/vetch pastures were evaluated under continuous grazing, at three stocking rates, using weaned lambs. The oats and oats/vetch mixture generally produced significantly more available above‐ground phytomass (AAP) than the vetch pasture. No significant differences in AAP or average daily gain (ADG) were measured between stocking rates on the different pastures. The levels of food availability and animal production obtained with the different pastures indicate that oats, vetch and an oats/vetch mixture can be used as annual, wintergreen pastures in the eastern Cape sourveld. However, the stocking rates that were implemented were too low to determine the production potential of the different pastures and an evaluation of the pastures at higher stocking rates is recommended before any recommendation on optimal stocking rates can be made.     

Sequence and process of species selection by cattle in relation to optimal foraging theory on an old land in the Natal Sour Sandveld

The sequence in which cattle grazed four grass species during a grazing period was monitored at four stages through the grazing season. Data collected revealed that: (i) species could be classed as being of preferred, avoided or intermediate acceptability, (ii) grazing of classes always proceeded in a set sequence; cattle first grazed preferred, then intermediate classes but largely resisted grazing avoided species, (iii) classes were grazed at different rates through the grazing period, (iv) utilization of intermediate and avoided classes was largely dependent on the extent of grazing of preferred species and exhibited a threshold relationship and (v) observed trends were in general agreement with those predicted on the basis of optimal foraging theory. The data suggests that non‐selective grazing systems may be based upon faulty grazing philosophy.     

Seasonal grazing capacity of an irrigated grass/legume pasture in the Rûens area of the southern Cape

Seasonal changes in grazing capacity of an irrigated grass/legume mixture consisting of lucerne, red clover, white clover, tall fescue, cocksfoot and perennial ryegrass were determined in the Rûens area of the southern Cape. Applying variable stocking rates and three grazing pressures (1,5; 2,25 and 3,0 kg DM/dry sheep‐unit/ day) in a six‐paddock grazing system, it was found that the mean annual stocking rate for maximum wool yield was 54,4 dry sheep‐units/ha over a period of three years. The seasonal grazing capacity of the pasture varied throughout the year and dry matter availability was most limiting during winter and highest during spring. The clover component of the pasture was depressed by the high grazing pressure and declined with age, while the grass content increased proportionally. The proportional lucerne content of the pasture material was more stable and was promoted by the high grazing pressure, but was not influenced by increased pasture age.     

How could herd mobility be used to manage resources and livestock grazing in semi-arid rangeland commons?

Pastoralists in Namaqualand, South Africa, use herd mobility to manage livestock and rangeland resources. However, their socioeconomic conditions and ecological landscapes are changing and we explore the options that are available for pastoralists to respond to these changes. This paper presents five possible scenarios for managing livestock in rangeland commons in semi-arid Namaqualand and outlines some of the major advantages and disadvantages associated with each scenario. Scenarios in response to drivers of change include (1) maintaining the status quo with an assumption that current mobility practices are adapted to local environments, (2) integrating new lands into the existing commons for use by mobile pastoralists, (3) using existing lands under existing mobile pastoralism conditions but introducing grazing reserves for use in times of drought, (4) amalgamating herds into larger units under the care of skilled herders, and (5) developing commercial-scale farms for single-occupancy owners because government might be pressured to further promote black commercial farmers to deracialise the commercial farming sector in South Africa. We consider these scenarios as starting points for discussions on future management options that pastoralists in Namaqualand may wish to consider as the managers of rangeland commons.     

放牧绵羊排泄物在荒漠草原土壤内的养分降解

试验研究了放牧绵羊粪便在内蒙古短花针茅草原土壤内的降解。结果显示:羊粪干物质的降解率为0.74mg.g-1.day-1,有机物质、C和N含量在一年的试验期间分别降解了25.0%、35.5%和16.6%;各成分间的降解有显著的相关性,其降解符合回归曲线方程为y=y0+a(1-e-bx);夏季是羊粪分解的主要时期。     

基于GIS的贵州西部春薯种植气候适宜性精细化区划

以贵州西部地区15个气象观测站1978-2010年的气候资料为基础,采用地理信息系统(GIS)技术,对春薯进行气候适宜性区划,为贵州春薯生产安全布局、品种调整提供科学依据。通过分析马铃薯平均气象产量与同期气候因子的关系,得出春薯的气候适宜性区划指标有8个:海拔高度、生育期平均气温、>10℃活动积温、降水量、日照时数以及7月平均气温、7-8月昼夜平均温差、5-7月降水量,每个指标分3级,对应最适宜、适宜和次适宜。通过对各站点的气候资料及其对应的经度、纬度、海拔高度、坡度和坡向等基础信息数据,应用多元线性回归方法,建立区划指标的空间分析模式。依托GIS技术空间分析功能,运用模式进行网格距为100m×100m以及精确到贵州西部地区乡(镇)的精细化气候区划,得到春薯最适宜区占贵州西部面积的52%,适宜区占45%,次适宜区占3%。