The structure of the soil in the arable layer is controlled by tillage, soil biota activities and weathering, whereas the structure below this layer is mainly the result of the activities of soil biota. Organic farmers tend to minimise the depth of the main tillage operation to encourage soil biota to create a soil structure with continuous biopores and a well crumbled topsoil. The best main tillage operation for preventive weed control, especially important in organic farming, is mouldboard ploughing. The shallow ploughing experiments described in this paper were conducted to ascertain the minimum ploughing depth for an ecologically accountable, sustainable tillage system with good weed control, good land qualities (in terms of workable days, aeration and soil moisture conditions) and finally with good yields. The “ecoplough” used for shallow ploughing was developed by Rumptstad Industries to meet the requirements of relatively shallow ploughing with good soil inversion for weed control. The plough has seven or eight bottoms for ploughing depths of 0.12–0.20 m, a working width of 2.1 m and a working speed of 1.7 m s−1. Its width is such that the tractor with wide low-pressure tyres runs on top of the land.
After using the plough for 6 years on Luvisols (>200 gkg−1<2 μm) in the IJsselmeer polders and on Luvisols (120–160 gkg−1<2 μm) in polders near the northern coast of The Netherlands, it was found that compared with conventional ploughing, shallow ploughing required less energy and labour and produced a relatively smooth surface. The latter facilitates the preparation of a seedbed consisting of relatively fine, strong, stable and moist aggregates. Organic matter, soil biota and nutrients were concentrated higher in the profile, influencing the workability of the soil, the growth of weeds and the growth of crops. Most of the yields were similar to yields after conventional ploughing, but weed populations increased when ploughing depth was <0.2 m. It was concluded that for organic farming on “active” soils (soils subject to shrink/swell with >200 g kg−1<2 μm), shallow ploughing seems to be the best reduced tillage system. It has several advantages. The main factor determining the minimum ploughing depth is control of weeds, especially of perennials. 相似文献
This paper describes successes and complications in eutrophication abatement in the Naardermeer nature reserve, The Netherlands. Restoration of this lake started in 1985. The main measure was the reduction of external nutrient load by the supply of phosphate-free water. Water quality and aquatic vegetation were monitored and the usefulness of a modelling approach in designation of management programs was investigated. The monitoring showed that for the first 4 years, recovery was retarded, possibly because of phosphorus release from the lake-bed sediments. After 10 years, turbidity was reduced and characteristic vegetation with Najas marina and Characeae species had re-established in large parts of the lake. Due to spatial heterogeneity it appeared necessary to dredge the lake-bed sediments locally. The model predicted most changes in aquatic vegetation correctly, indicating its predictive value. However, to predict restoration perspectives for rare species, expert judgement still remains necessary. Suggestions are made for selection of successful management measures depending on the conditions of lake ecosystems. 相似文献
