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11.
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
12.
Abstract. Usual residue-management options are to remove the residue, use it as mulch with or without undercutting or to incorporate it into the soil. While the role of surface mulch in evaporation has been widely studied, the information on the effect on evaporation of mulch with undercutting or residue incorporated into soil, particularly in relation to soil type and evaporativity (Eo) is lacking. We studied the effect of wheat straw used in various ways on the course of evaporation loss from soil columns with three soils at Ludhiana, India and one soil at Bushland, Texas, USA, under two Eo's Energy-limited evaporation rates under mulch (Eom) followed the soil-specific relation Eom/Eo= a e(bRes+cEo), where Res is residue rate t/ha and a, b and c are constants; Eo, is expressed in mm/d. In an effort to model the total evaporation (CE) during the energy-limited stage ‘U’ was obtained from appropriate CE versus time curves and (CE-U) was regressed over (t - ti)0.5 to obtain the slope ‘α’ (Ritchie 1972) for the soil-limited evaporation stage. The observed ‘U’ was independent of mulch rate and Eo but was strongly affected by soil type, Values of ‘α’ decreased with increase in mulch rate and decrease in Eo and coarseness of soil. The otherwise short lived benefit of evaporation reduction with mulch per se, which peaked after a few days was maintained when residue was mixed with soil at the stage when evaporation reduction reached a maximum; this benefit continued for several weeks. Cumulative evaporation values computed from ‘U’ and ‘α’ agreed closely with the observed values under straw mulch for loamy sand and clay loam soils and for ‘undercut’ and ‘residue mixed’ treatments on all soils regardless of Eo, and for all situations under small Eo. However, for sandy loam and silt loam soils under Eo of 10 mm/d, the modified square root of the time function of Jalota et al. (1988) gave a better fit. 相似文献
13.
重迎茬亚麻生长发育障碍机制的研究 总被引:2,自引:0,他引:2
重迎茬亚麻减产是由多种因素综合作用的结果,亚麻重迎茬可使病害加重是最主要因素,重茬年限越久发病越严重;重迎茬造成了土壤营养元素的单一消耗,随着重迎茬年限的增加,土壤中速效氮、速效磷、速效钾等含量降低。 相似文献
14.
Variation of Parthenium hysterophorus in response to soil quality: implications for invasiveness 总被引:1,自引:0,他引:1
Summary The performance of Parthenium hysterophorus , native to the tropical Americas and invasive to several countries, was evaluated for response to soil quality. Phenological (six stages) and quantitative growth variables [relative growth rates in height (Rh ) and diameter (Rd )] were measured every fortnight. Based on harvest data, the variables, root:shoot (R:S) ratio, specific leaf area (SLA), relative growth rate in biomass (Rw ), net assimilation rate (NAR) and dry matter allocation to plant components, were determined. High clay content in soils prolonged the rosette stage, enhanced Rh and Rd and hampered root growth, but promoted biomass allocation to shoots. The extreme degree of plant mortality was observed, with only 33.3% individuals surviving to reproduce in the soils with highest clay contents. This appears to be one of the most important findings that certainly has a major bearing on the range of adaptation of the weed. Seed mass declined whereas seed production increased in relatively coarser soils with the exception of nearly pure sand. In soils rich in clay, plants produced a smaller number of larger seeds. These data suggest that variation in fundamental functional traits would enable P. hysterophorus to adjust to a variety of habitat conditions. 相似文献
15.
通过12a大田长期定位试验研究了在自然降水条件、冬小麦—大豆轮作(或休闲)种植制度下,0~400cm土娄土剖面硝态氮分布与积累的特点。结果表明,长期单施氮肥,氮的表观利用率特别低,仅0.51%,氮肥配施钾、磷肥,氮的表观利用率为25%~35%,氮磷钾平衡施肥及配施有机肥,氮的表观利用率达到50%;施N肥方式显著影响土壤硝态氮积累和淋移,旱地土娄土长期单施化学氮肥或氮钾、氮磷、氮磷钾肥使土壤NO-3-N大量积累和淋移;氮磷钾与有机肥的配合施用能有效地缓解土壤对硝态氮的积累,提高氮肥利用率。 相似文献
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为探究不同氨基酸菌肥施用量对茶树生长和土壤肥力含量的影响,以鸿雁12号茶树为研究对象,采用田间微区试验的方法,设置了不施用氨基酸菌肥作对照组(CK)和氨基酸菌肥施用量分别为75 kg·hm-2(T1)、150 kg·hm-2(T2)、225 kg·hm-2(T3)和300 kg·hm-2(T4)的处理,研究不同氨基酸菌肥施用量对茶树生长、茶叶品质及土壤肥力的影响。结果表明:氨基酸菌肥施用后能显著增加茶叶芽头密度及茶叶产量,提高茶叶中氨基酸含量和土壤中碱解氮含量。试验6个月后与CK相比,T4组的芽头密度显著增加了63.4%,茶叶产量显著增加了71.5%;T1~T4处理茶叶中氨基酸含量分别增加了9.73%、6.41%、7.57%和13.2%,土壤中碱解氮含量分别增加了25.0%、36.0%、46.0%和37.6%。综上,氨基酸菌肥的施用能提高茶叶产量及品质,改善茶园土壤环境质量,为茶园生产的合理施肥及优质高效生产提供数据参考。 相似文献