粤北低山坡地营造梯田对土壤磷组分及有效性的影响

【目的】探明粤北低山坡地营造梯田对土壤磷形态分布特征和有效性的影响。【方法】选择该区域花岗岩发育的自然林地(FL)、旱作梯田(UT)和稻作梯田(PT)土壤为对象,对土壤剖面不同土层理化性质、磷组分含量及有效性进行测定。【结果】与自然林地FL相比,旱作梯田UT和稻作梯田PT土壤0～20 cm土层有效磷和磷活化系数(PAC)明显增加,以PT最高;3种利用方式土壤有机磷(OP)和无机磷(IP)在剖面中总体表现为"C"字型变化趋势,且均以表层土壤含量最高;与FL相比,UT和PT土壤以IP为主,Fe-P和O-P所占比例较高,其中O-P的比例从7.69%～13.58%上升到22.97%～41.96%;通径分析和冗余分析结果显示,OP是该区域土壤磷有效性的敏感磷源,而游离铁和有机碳是驱动土壤磷组分转化的关键性因子。【结论】粤北低山坡地营造梯田改变了磷在土壤剖面中的分配格局,提高了磷的有效性,也增加了土壤无效态磷的比例。     

黄土高原坡改梯综合效益分析——以燕沟流域为例

 退耕坡地是近年来黄土高原整治生态环境和控制水土流失的关键措施,但对于如何退耕,学术界存在多种不同观点,实践方面存在多种不同模式。以延安燕沟流域坡改梯为例,利用2005年延安站的逐日气象数据和燕沟流域地貌、土壤及土地利用等资料,借助WIN-YIELD软件,对不同地形坡度条件下坡改梯在作物增产、保水减沙效益以及燕沟流域坡改梯实践效果进行模拟、对比和实证分析。结果表明:地形坡度越大,坡改梯作物增产、保水和减沙效益越显著;坡度小于5°的坡耕地可以不进行梯田改造,坡度大于15°的坡耕地应及早实施坡改梯或退耕还林(草)。     

The impact of alley cropping Gliricidia sepium and Cassia spectabilis on upland rice and maize production

G. sepium and C. spectabilis hedgerows were established on slopes ranging from 18 to 31% in an effort to reduce soil erosion and improve upland rice and maize production. Upland rice and maize responded more to soil incorporated G. sepium biomass than to mulched, C. spectibilis. Incorporating hedgerow biomass equivalent to over 40 kg N per hectare, however, did not increase upland rice productivity. Maize, planted during the drought-prone second season, responded more than did rice to mulching. Crop performance improved along the slope gradient. Hedgerow-crop competition was observed at the upper and lower interfaces. Terracing intensified hedgerow-crop competition at the upper interface by reducing the crop's effective rooting depth. Under prevailing climatic and soil conditions, mixed hedgerows of C. spectabilis and G. sepium initially produced approximately 7 tons of fresh biomass per hectare every 3 months. Four years after hedgerow establihment, however C. spectabilis biomass was chlorotic and considerable mortality was observed, suggesting that C. spectabilis may be depleting soil N reserves.     

典型岩溶坡面土壤水分的空间变异研究

选取典型岩溶区顺坡和土地整理后的坡改梯土壤水分空间分布为研究对象,应用地统计学与GIS技术,将土壤水分室内布点和实地监测相结合,对果化示范区进行两个坡面的网格布点和坡面土壤水分空间变异研究.结果表明:顺坡地和土地整理后的坡改梯两个坡地的空间分布存在一定程度的全局空间正相关;两个坡地的空间聚集区和空间孤立区呈现出类似的高-高集聚和低-低集聚明显,而孤立区零星分布的特征;两个坡地均符合球状模型,顺坡地的土壤水分受坡面情况的影响较大;土地整理后的坡改梯土壤水分主要受地形条件和人为因素共同作用的影响;顺坡和土地整理坡地的土壤水分的最小空间变程分别约为90 m和135 m,可作为不同类型坡面土壤水分样点间隔的布设依据.研究结果对于指导典型岩溶区农业生产、保障区域土壤资源可持续合理利用具有重要的理论意义和参考价值.     

Best management practices for agricultural non-point source pollution in a small watershed based on the AnnAGNPS model

Best management practices (BMPs) are implemented to reduce non-point source pollution (NPSP) worldwide. In this study, the AnnAGNPS model was adapted and used to evaluate the effectiveness of BMPs for NPSP control in the Three Gorges Reservoir Area in China. Through field investigation and experimental observation, the AnnAGNPS model database was constructed. The model best simulated run-off and its simulation of total nitrogen (TN) was better than for total phosphorus (TP). Simulation of the spatial distribution of different pollutant loads showed that the annual outputs of TN and TP per unit area were the highest, with an average of 63 and 6 kg hm⁻² per year, respectively. An optimal scenario was developed based on adjustments to the existing land structure which were most effective at reducing N and P loads. The reduction rates of TN and TP loads were 54% and 63%, respectively, while the reduction rates of dissolved and particulate N and P loads were between 47% and 68%. After 27% of arid slope fields were converted into terraces in the study area, the modelled particulate N and P outputs were reduced by 44% and 46%, respectively, showing that terracing sloping land could be effective at reducing particulate N and P losses. These findings indicated that slope-shifting technology is the most important method for NPSP control in the TGRA. In addition, reduced fertilizer use and conservation tillage measures should also be adopted to effectively reduce TN and TP losses.     

Effects of soil conservation on soil properties of citrus orchards in the Three‐Gorges Area,China

Mountain region citrus production systems occupy large parts of the landscape prone to soil erosion in the Three‐Gorges Area of China. Several soil conservation measures, such as terracing hedgerows, are widely implemented in citrus orchards to control soil erosion. However, little is known about the effect of those measures on soil properties. The objective of this work was to analyse the changes of soil properties in citrus orchards subjected to different conservation measures. Experiments were conducted in four plots: control plot (SC, sloping orchard without conservation measures), sloping orchard with contour hedgerows (SCH), terraced orchard (TC) and terraced orchard with grass cover (TCG). Samples of soil surface from 0 to 15 cm were collected to analyse texture, bulk density (BD), aggregate stability, saturated hydraulic conductivity, soil organic matter (SOM) and soil nutrients. The spatial variability of those properties was also evaluated at slope and field scales. The results showed that the three conservation measures significantly increased saturated hydraulic conductivity, aggregate stability, SOM and available N, P, K, but decreased BD. The terracing with grass cover measures were the most effective in improving soil fertility among the three measures. The average SOM, available P, N, K in TCG were 0·27, 0·50, 1·74 and 1·72 and these rates are larger than for the in SC. Compared to SC, silt content was increased the SCH, while clay content was increased with TC and TCG. There was a downslope increase in clay content and total N but a decrease in gravels in the SC plot. However, that trend did not exist in the other plots. At the field scale, the soil aggregate stability and total nitrogen were significantly higher near the hedgerow under SCH, and the available N was significantly higher in the middle position under TC; the other soil properties had no significant trends based on the distance to hedgerow or stone bunds. Results of this study will contribute to a further understanding of the environmental influence of soil conservation measures. Copyright © 2010 John Wiley & Sons, Ltd.     

半干旱黄土区水平阶整地人工油松林地土壤水分和养分状况

水平阶整地是半干旱黄土高原丘陵沟壑区普遍应用的一种抗旱造林措施。为研究水平阶整地措施对人工油松林的影响,对20a高密度人工油松林样地的土壤水分和养分状况进行了研究。结果表明,雨季末各样地0—160cm土层的平均土壤含水量为5.43%,其中0—60cm土层为6.94%,60—160cm土层为4.53%,雨季对各样地的土壤水分补给量很小;碱解氮、速效磷、速效钾、有机质和全氮具有表聚性,尤其是0—10cm土层表聚性显著,全磷和全钾表聚性不明显;各样地pH值均大于8;0—100cm土层的全磷、速效磷、全钾和速效钾平均含量为中等水平,有机质、全氮、碱解氮为低或很低水平。结果说明在半干旱黄土区降水量不足的情况下,人工植被密度如果过大,会恶化土壤水分和养分的状况,所以人工疏伐就成了人工林后期管理和经营中必要的环节。     

西南山区等高植物篱和植物固结地埂的水土保持功能的理解

水土流失是个世界范围的严重环境问题,比如由于丰沛的降雨和陡坡耕作,造成的中国西南部偏僻山区的坡耕地水土流失.这些区域采取了多种保持土壤措施减少土壤流失,可当地农民并不接受引进的等高植物篱措施;而植物固结地埂是一项传统的且当地农民乐意接受的水土保持措施.本文比较了等高植物篱和植物固结地埂的结构,设置3种植物固结地埂高度0 (CK)、10cm (H10H)、和15 cm (H15H),分析了等高植物篱(H0H)和上述3种地埂高度的植物固结地埂对径流、侵蚀量的影响及产投比和经济效益,旨在理解当地农民的选择.研究结果显示最明显的区别是植物固结地埂具有一定高度的地埂能够方便农事活动并且有效减少水土流失.植物固结地埂的第2个处理(H15H)比无地埂无植物篱的坡耕地处理(CK)减少径流55.56％±6.25％,减少侵蚀量79.26％±3.50％.不同处理的径流量、土壤侵蚀减少量和土壤抗蚀性变化顺序为:H15H＞H10H＞H0H＞CK.H15H的产投比最高为1.52.与其他试验处理相比,虽然H15H措施需要的劳动力更多,但它具有较高的植物篱收获量和产投比以及较强的抗冲蚀性.因此,西南地区坡耕地上推荐具有15 cm地埂高度的植物固结地埂措施(H15H),甚至该项水土保持措施可适用于与西南地区气候相似的其它区域或是其它国家.     

贵州省岩溶山区旱坡耕地梯化的环境效应研究

1997～1999年3年时间,在田间生产条件下,研究贵州岩溶山区旱坡耕地梯化的环境效应,结果表明：可防治水土流失和石漠化扩展;为大于25度的旱坡耕地退耕还林,准备了较好的立地条件;提高小于25度旱坡耕地的粮食作物产量近20%,为陡坡耕地顺利退耕提供物质保障;本旱坡耕地梯化技术,操作简便、易行,投资少,见效快。     

茶园坡改梯配套技术及生态效益研究

坡地茶园土壤流失比较严重,特别是新植茶园。提高茶园土壤覆盖度是减少茶园土壤侵蚀的有效手段。重庆地区山地茶园实行坡改梯后,再配套绿肥等复合种植技术及开沟集中深度施入速效追肥技术,提高茶园覆盖度,可显著提高坡地茶园持续的保土保水保肥能力,其土壤年侵蚀量仅为64．3～174．2kg／667m^2,是降低山地茶园土壤侵蚀,形成山地茶园生态栽培的有效模式。