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1.
Abstract. In Australia, stubble burning and tillage are two of the major processes responsible for the decline of soil organic carbon concentration in cropped soils, and the resulting soil degradation. However, the relative importance of these two practices in influencing the soil organic carbon concentration and the long-term impact on soil quality and productivity are not clear. The effects of stubble burning as practised by farmers in southeastern Australia were evaluated in two field trials, one of 19 years duration, the other of 5 years. Conventional tillage (three tillage passes) led to greater loss of soil organic carbon than stubble burning. Loss of total soil organic carbon attributed to stubble burning in the 0–10 cm layer was estimated to be 1.75 t C ha−1 over the period of the 19-year trial, equivalent to 29% of that lost due to tillage. In the 5-year trial, no change in soil organic carbon due to stubble burning was detectable. Changes in soil quality associated with stubble burning detected in the longer trial included a reduction in macro-aggregate stability, and increases in pH and exchangeable K+ . Only the latter two were detected in the shorter trial. A higher mean wheat yield (average 0.15 t ha−1 ) following stubble burning was observed in the 19-year trial but not in the 5-year trial. Research to monitor the longer term effects of stubble burning is needed, and to identify conditions where loss of soil organic carbon is minimized. 相似文献
2.
3.
对湖南省森林的固土保肥、改良土壤和净化大气效益进行了计量评估,结果表明由于对森林的保护,每年,湖南省少流失的土壤234.37×10 相似文献
4.
《Scandinavian Journal of Forest Research》2012,27(2):142-151
The effects of timing and intensity of precommercial thinning were studied in three Scots pine artificially regenerated stands on Vaccinium forest sites in southern Finland. A two-level factorial design (3×3) was used in each stand: thinning at dominant height of 3, 6 and 9 m to 1000, 1600 and 2200 stems ha?1. The effects of the treatments were analysed after a period of 23–25 yrs when the dominant height was 14–15 m. Early thinning resulted in the highest standing volume and amount of merchantable wood, and also in slightly accelerated height development. Thinning to 1000 stems ha?1 caused a considerable production loss, but there were no differences between the densities of 1600 and 2200 stems ha?1. Branches became thicker after early thinning, but the differences between the treatments were negligible for crop trees. Crown ratio was lowest as the result of early or moderate thinning (2200 stems ha?1). 相似文献
5.
Haiyang Liu Zhanfeng Hou Zhi Chen Pei Wu Chuanzhong Xuan Hongbo Wang 《Land Degradation u0026amp; Development》2019,30(3):328-336
Crop residues, particularly standing stubble, can reduce soil erosion by wind in conservation tillage. To determine the optimum architecture of standing stubble for effective reduction of wind speeds near the soil surface, we quantitatively analyzed the interception effect of standing stubbles on soil erosion particles through pure wind experiments and sand‐bearing wind experiments. The relationship between stubble height, row number, and interception rate was also revealed. The study was conducted in a wheat field under conservation tillage. Three representative heights of standing stubble were tested: 10, 20, and 30 cm. All had an average plant density of 400 plants m−2, row spacing of 20 cm, and an average stubble cover of 52%. A wind‐tunnel was placed over the stubble, and the central wind speeds were selected at 6, 9, 12, 15, and 18 m s−1. During the experiments, the blowing time was set for 10 min, and 1,404 g of local soil from the experimental area was fed into the wind‐tunnel. A sand collector was placed at the 16th, 19th, 23rd, 27th, and 31st stubble row away from the air inlet of the wind‐tunnel to measure the amount of soil eroded by wind at different stubble heights under conditions of blank and sand‐bearing winds. The concept of ‘interception rate’ and its corresponding formula were proposed. The interception rates of 10‐cm and 20‐cm high stubbles were lower than those of 30‐cm stubble and decreased sharply, particularly at wind speeds >12 m s−1. Even at the wind speed of 18 m s−1, the interception of wind erosion particles with 30‐cm high stubble at 16th, 19th, 23rd, 27th, and 31st rows were 20.85%, 41.55%, 60.46%, 80.59%, and 85.96%, but only 5.75%, 24.76%, 39.32%, 62.39%, and 76.04% with 10‐cm high stubble at the same positions. The interception effect was similar at the 27th and 31st rows. However, more than 31 rows would be required of the 10‐cm stubble and 20‐cm stubble to intercept the same amount of wind erosion particles as with 27 rows of the 30‐cm stubble. The soil particle interception rate increased with an increase in the number of rows of standing stubble and decreased with an increase in wind speed. As expected, with additional rows of stubble, the amount of soil intercepted increased. Therefore, for a farmland that uses 400 plants m−2, leaves of 30‐cm high stubble with 52% cover, and has row spacing of ≤20 cm, the effective amount of standing stubble should be more than 27 rows. 相似文献
6.
Effects of human-mediated processes on weed species composition in internationally traded grain commodities 总被引：2，自引：0，他引：2
International trade is a major route by which non‐indigenous organisms are introduced into new habitats. Various kinds of weed seeds have been introduced through grain trade. The objectives of this study were to understand the factors that affect the initial assemblage of plant species introduced by the international grain trade and to extract their general attributes. We surveyed weed seed contamination of spring wheat imported from Canada to Japan and analysed the effects of the field abundance of each weed and of harvesting and cleaning on the quantity of weed seed included in the imported wheat. The field abundance was positively correlated with the weed seed quantity. Seeds of short weeds and seeds with a pappus were eliminated from the wheat by the harvesting or cleaning process. Many other crop plants contaminated the wheat. Because various transportation vehicles, temporary storage sites and port elevators are used commonly with all exported crops and it is difficult to remove all residues from them, other crops might be carried over into the wheat commodity. These relationships also apply to other grains. 相似文献
7.
The market for herbage seed straw has diminished in many seed-production areas due to less livestock. Seed growers are therefore looking for alternatives to straw removal, which up to now has been the most common practice. During 2000–2006, different alternative straw chopping methods, both at the back of the combiner and with a tractor-mounted flail-chopper, and field burning strategies were evaluated in seed crops of timothy (Phleum pratense) and meadow fescue (Festuca pratensis) in southeast Norway. The requirement for an extra N input in autumn (30–40?kg ha-1) when practising straw chopping was also examined. Compared to straw removal, straw chopping at the back of the combiner during seed harvest did not reduce seed yield in the following year as long as stubble height was low (<10?cm in timothy) and the straw spread uniformly in the field. On average, seed yield was 1–4% and 1–9% higher compared to straw removal in timothy and meadow fescue, respectively. If the chopped straw was spread unevenly, or long stubble was left at combining, it is recommended to use a tractor-mounted flail-chopper after harvest. The experiments did not provide any support for an extra input of nitrogen in autumn, either in timothy or meadow fescue, when the straw was chopped rather than removed. Burning of stubble and straw soon after seed harvest was another efficient clean-up method after harvest, which increased seed yield 9–15% and 17–20% compared to straw removal in the two species, respectively. However, as the burning method is risky and causes smoke emissions, it is normally not recommended. It is concluded that for most seed growers, the most effective, least laborious and most environment-friendly alternative to straw removal will be to chop the straw at the back of the combiner during seed harvest. 相似文献
8.
针对秸秆全量还田对收割留茬的要求,分析大型全喂入联合收割机改制二层割刀的可行性,设计了一种基于地轮仿形的收割机二层割刀。该套装置采用地轮仿形,实现了留茬高度一致,控制留茬高度低于25 cm。该结构实现了秸秆全量还田的要求,降低了收割机脱粒分离负荷,减少了一遍秸秆粉碎作业程序,在提高作业效率和质量的同时,合理降低了农机作业成本。 相似文献
9.
Summary Effects of temperature and daylength on the bolting of a number of B. campestris accessions were investigated both in the open and in the IVT phytotron. From the results it was concluded that low temperature and genotype are the predominant factors with respect to bolting. Daylength has rather limited influence. One cultivar bolted more than 12 weeks earlier at 10 and 14°C than at 18°C. On the other hand some cultivars did not require vernalization at all.At 14°C and short daylength, depending on genotype, the period of time between sowing and 50% bolting ranged from 8 to 30 weeks. At this temperature the stimulating effect of long day (24 h), depending again on the genotype, ranged from 0 to 4 weeks. The genotypes most resistant to bolting appeared to be the stubble turnips (B. campestris ssp. rapa).In terms of seed(ling) vernalization at 5°C the cold requirement ranged from 0 to more than 3 weeks, depending on the genotype. The required vernalization periods at 5°C can be used as a criterion in screening for resistance to bolting. 相似文献
10.
近年来大型养殖场不断出现,但养殖场的环境恶劣、工作强度大、工作效率低,为了解决养殖场工作人员的劳动强度,设计了适合养殖场的清扫机器人.以养殖场环境为依据,结合嵌入式系统,使用的微处理器是三星S3C2410,设计出的养殖场清扫机器人主要由通信模块、运动控制模块、传感器模块3部分组成.该机器人可以解决养殖场的诸多问题,提高工作效率. 相似文献