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1.
Continuous hourly records of soil temperature were collected at 1, 5 and 20 cm, throughout two growing seasons, 1973 and 1974, under crops of spring barley in the east of Scotland. Measurements were obtained from three cultivation treatments, deep ploughing, normal ploughing and direct drilling, at two nitrogen fertiliser levels, 0 and 150kg/ha. Compared with ploughed soil, direct-drilled soil had a higher surface reflection coefficient and a higher thermal diffusivity between 5 and 20 cm; overall, this resulted in lower heat sums (°C hours/day over 5 °C and 10 °C) in direct-drilled soil at 1 cm and 5 cm during the first 20 days after sowing. The thermal regimes of normally and deeply ploughed plots were very similar. Nitrogen fertiliser caused significant lowering of soil temperature at all three depths in the latter half of the growing season, due to increased shading of the soil surface by the crop canopy. Some implications of these findings for cultivations for cereals are discussed.  相似文献   

2.
Abstract. Experiments were conducted for one year on two different soil types. On a clay soil straw was either (a) burnt, (b) baled leaving the stubble, or (c) chopped and spread. The soil was tine cultivated to depths of 5, 10 or 15 cm or ploughed to 20 or 30 cm before winter wheat was sown conventionally. In addition, a direct-drilled crop was sown after each straw treatment. On a silt loam soil the direct-drilled, tine cultivated to 15 cm and ploughed to 30 cm treatments following burning or chopping and spreading straw were repeated.
Tine cultivation incorporated less straw than ploughing, decreased plant establishment and early growth but did not decrease yield. Direct-drilling through chopped straw decreased yield on the silt loam but not on the clay soil. Short straw (< 5 cm) was easier to incorporate than longer straw. Ploughing was the most efficient method of straw incorporation because it inverts soil. Early effects on crop growth and nutrient uptake following straw incorporation were transient and associated with large amounts of straw in the seeded layer of soil.  相似文献   

3.
In a long-term cultivation experiment on a sandy clay loam overlying magnesian limestone and cropped with spring barley (Hordeum sativum) each year, mouldboard ploughing, shallow tine cultivation and direct drilling were compared. Compaction had become evident on the direct drilled treatment and to alleviate this the ‘Paraplow’, a slant-legged soil loosening implement, was used on all treatments to a depth of 35 cm in the autumn of 1980.A crop of spring barley (var. Athos) was grown in 1981, at a nitrogen fertiliser rate of 75 kg ha?1 N. Root growth, shoot dry matter, nitrogen uptake, grain yield and components of yield were recorded. Soil strength (by cone resistance) and dry bulk density of the soil were also measured. As a mean of all cultivation systems the ‘Paraplow’ increased grain yield by 12%. The response of the crop to cultivation by the ‘Paraplow’ was greatest on the mouldboard ploughed and long-term direct-drilled systems. The latter out-yielded the former, with shallow tine cultivation intermediate.The decrease in soil strength caused by the ‘Paraplow’ resulted in more rapid penetration of root axes and greater proliferation of roots in each horizon of the profile. There was no significant effect on shoot dry matter up to anthesis but, at harvest, barley on land treated with the ‘Paraplow’ had more ears with more grains per ear. Thousand-grain weight was not affected.The poorer growth of barley on ploughed than direct drilled land in 1981 was explained by temporary waterlogging of the soil in May.  相似文献   

4.
The nitrate content of three heavy clay soils (Evesham, Denchworth and Lawford series) was examined after direct drilling or ploughing, and of another clay soil (Denchworth series) with or without mole drainage and after tine cultivation. Autumn-sown crops were grown at all these sites during the years 1973–80. Except in 1974–75, the nitrate concentration of the soil solution sampled from direct-drilled plots was less than from the ploughed plots, particularly in late autumn and early winter. By January the plots which had been ploughed contained 12–65 kg N ha?1 more mineral nitrogen than direct-drilled plots, but differences between cultivation treatments disappeared rapidly and had gone by early March. After tine cultivation, the nitrate content of the soil profile was not affected by the contrasting drainage status of the plots with or without mole drainage. These results support the view that although denitrification can be greater in direct-drilled soil, the larger nitrate concentrations present in ploughed soil result from the soil disturbance exposing less accessible substrates to mineralization by microbes. By this means, considerable amounts of mineral nitrogen are made available at the beginning of the winter, during the establishment of autumn-sown crops.  相似文献   

5.
Vane shear strength, water status and bulk density were measured at various times in a growing season at two depths in a swelling clay topsoil. The site comprised experimental plots that had been ploughed annually, or direct-drilled for 10 years; short-term fallow areas, created on adjacent long-term grassland, were compared with the arable plots. In the middle of the topsoil layer (nominally 120 mm depth) of all three treatments shear strength was linearly related to water content, and similarly to bulk density in the direct-drilled and ploughed soils. Closer to the soil surface (nominally 40 mm), relationships between strength and wetness or density were less distinct, particularly in the spring, when drying was not accompanied by an increase in strength; possible reasons for this anomaly are considered. The shear strength of the untilled soils was greater, at both depths, than that of the ploughed soil. Other factors including density, water potential, soil structure and organic constituents, differed with time or between treatments, and their contribution to variations in shear strength are discussed.  相似文献   

6.
The effects are repotted of direct drilling and mouldboard ploughing on soil water retention and extraction in three soils over two to four years. In the years 1972–75 when winter rainfall was close to or greater than the long-term average the maximum soil water content of the upper 100 cm differed little between the cultivation treatments. In contrast, after the dry winter of 1975–76, about 10 per cent more water was stored in the direct-drilled soil, especially below 50 cm. In the following dry summer, winter wheat extracted up to 22 mm more water from uncultivated soil and this was associated with better growth of the crop than after ploughing. When simulated rain was applied, water infiltrated rapidly to a depth of 50–100 cm in direct-drilled soil, whereas on ploughed land its movement was retarded below the plough sole even when cultivation had been carried out under conditions which minimized smearing. Water storage at depth was consequently greater under dry conditions in the direct-drilled soil while excess water reached drain depth more rapidly in wet conditions.  相似文献   

7.
The leaching of nitrate-N under autumn-sown arable crops was measured using hydro-logically isolated plots, about 0.24 ha in area, from 1984–1988. Fluxes of water and nitrate moving over the soil surface (surface runoff), at the interface between topsoil and subsoil (interflow), and in the subsoil (drainflow) were monitored in plots with mole-and-pipe drain systems (drained plots); surface runoff and interflow only were monitored in ‘undrained’ plots. Half the drained and undrained plots were direct-drilled, and on the other half seedbeds were prepared by tillage to 200 mm. Tillage increased the total leaching loss of nitrate by 21 % compared with direct drilling in drained plots. About 95% or the nitrate moving from the soil was present in the water intercepted by the subsoil drains in these plots. In undrained plots less water and nitrate were collected in total; more of the nitrate was present in interflow on ploughed plots and in surface runoff in direct-drilled land. Losses of nitrate for the whole experiment from 1978-1988 were analysed. This showed that, between the harvest of one crop and the spring application of fertilizer to the next, loss of nitrate-N from ploughed land (Lp) was approximated by Lp=22+Fkg N ha?1, where F was the autumn fertilizer-N applied. After fertilizer was applied in spring, loss of nitrate-N depended on rainfall such that for 100 mm rainfall about 30% of the fertilizer-N was lost by leaching. About 18% more nitrate-N was lost from direct-drilled land than from ploughed land in spring, but the total loss was generally small compared to that over winter. The apparent net mineralization of organic-N was measured in 1988. In autumn and winter there was little effect of tillage treatment (26 and 31 kg N ha?1 on direct drilled and tilled plots respectively). However, over the year 83 kg N ha?1 were mineralized in tilled plots, and 67 kg N ha?1 in direct-drilled plots. Five factors governing the leaching of nitrate are assessed and this identified that fertilizer nitrogen application to the seedbed of winter sown crops and the mineralization of nitrogen from the residues of the previous crop are the most significant factors for nitrogen leaching in the UK.  相似文献   

8.
The underlying question of these investigations asked, how and to which extent rape plants react with transpiration and soil water uptake to different degrees of nitrogen fertilization. Therefore repeated campaigns with concurrent measurements of plant surfaces (leaves, stems, pods), diurnal courses of leaf transpiration and root length density of rape plants growing on heavily (240 kg ha—1), moderately, (120 kg ha—1), and nil N‐fertilized plots of an experimental field in northern Germany were performed during two growing seasons. Additionally, matric potentials at different soil depths were measured. In the first year (1994) investigations were concentrated primarily on shoot area development and transpiration, whereas in the subsequent year (1995) root measurements were mainly undertaken. Also, the influence of soil management (ploughing, conservation tillage) was taken into consideration. The plots where the shoot measurements were carried out were ploughed in 1994 and rotovated in 1995. Matric potentials were measured in both years in ploughed soil and, for comparison, also in soils with conservation tillage. Shoot area index, as measure of the transpiratory capacity of the canopy, increased on ploughed soil and reached a maximum before flowering. Thereafter it decreased until harvest when the relative amount of green stems and pods was increasing. Then, the measured transpiration rate per pod surface area was equal to, or higher than, the transpiration rate per leaf surface area. Plant surface area was smaller in plots with conservation tillage and decreased generally with decreasing N‐fertilization. Increasing plant surface area was joined by an increasing density of plant canopy. Light interception was thus highest in the plots receiving 240 kg N ha—1. Although the shading effect may cause a reduction of transpiration per plant, the total plant mass per area generally resulted in a greater water loss from these plots. Roots reached at least 110 cm depth. Root length density was significantly higher in the upper 10—30 cm of soil than at greater depths. Root mass was smaller in soil with conservation tillage than in ploughed soil. Oscillations of soil matric potentials in the diurnal and long‐term periods were highest in the upper 10 cm of soil. Here, they corresponded well with the cumulative diurnal transpiratory water loss. It is concluded that the soil water dynamics depends largely on the distribution of plant roots. As a result, rape plants did not change their specific transpiration capacity as a response to increased nitrogen fertilization. However, the transpiring plant surface and root length density increased the turnover rate of water by a higher plant density per plot. This effect was more pronounced in ploughed than in rotovated plots.  相似文献   

9.
Information is needed about root growth and N uptake of crops under different soil conditions to increase nitrogen use efficiency in horticultural production. The purpose of this study was to investigate if differences in vertical distribution of soil nitrogen (Ninorg) affected root growth and N uptake of a variety of horticultural crops. Two field experiments were performed each over 2 years with shallow or deep placement of soil Ninorg obtained by management of cover crops. Vegetable crops of leek, potato, Chinese cabbage, beetroot, summer squash and white cabbage reached root depths of 0.5, 0.7, 1.3, 1.9, 1.9 and more than 2.4 m, respectively, at harvest, and showed rates of root depth penetration from 0.2 to 1.5 mm day?1 °C?1. Shallow placement of soil Ninorg resulted in greater N uptake in the shallow‐rooted leek and potato. Deep placement of soil Ninorg resulted in greater rates of root depth penetration in the deep‐rooted Chinese cabbage, summer squash and white cabbage, which increased their depth by 0.2–0.4 m. The root frequency was decreased in shallow soil layers (white cabbage) and increased in deep soil layers (Chinese cabbage, summer squash and white cabbage). The influence of vertical distribution of soil Ninorg on root distribution and capacity for depletion of soil Ninorg was much less than the effect of inherent differences between species. Thus, knowledge about differences in root growth between species should be used when designing crop rotations with high N use efficiency.  相似文献   

10.
The concentration of oxygen at three depths (15, 30 and 60 cm) has been measured in a direct-drilled or ploughed clay soil of low hydraulic conductivity (Evesnam series) which was cropped with winter wheat in three consecutive growing seasons (1972/73 to 1974/75). The mean oxygen concentrations between January and March varied with the seasonal rainfall; in the relatively dry winter of 1972/73they were 20 per cent (v/v) at 15 cm and 12 per cent (v/v) at 60 cm, but in the wetter winters of 1973/74 and 1974/75 they were less than 11 and 6 per cent (v/v) at 15 and 60 cms respectively. Direct drilling resulted in higher oxygen concentrations at 15 cm than ploughing in both wetter winters, the mean concentration being 10.2 and 7.2 per cent (v/v) in direct-drilled and ploughed plots respectively. Frequency distributions of values obtained at individual sampling points showed that when the mean oxygen concentration of the soil at 15 cm decreased to its annual minimum (in January-March), a significantly higher proportion of the sampling points under direct drilling continued to show concentrations of oxygen greater than 10 per cent (v/v). The results are interpreted as indicating that the higher oxygen concentrations found in this soil after direct drilling are due to the development of a system of continuous large pores and channels which would otherwise be destroyed by annual ploughing.  相似文献   

11.
EFFECT OF PLOUGHING AND DIRECT DRILLING ON SOIL NITRATE CONTENT   总被引：4，自引：0，他引：4  
The concentration of nitrate-N at 30 cm depth in a clay soil was 2–5 times greater (p<.05) after ploughing than after direct drilling during the winter and spring of 1972–3. However, by early May no significant differences could be detected between cultivation treatments. It is concluded that decreased mineralization of soil nitrogen in the direct-drilled soil is the main factor responsible for the differences observed.  相似文献   

12.
Numbers of earthworms collected from direct-drilled or ploughed land were studied during successive years on contrasting soil types sown with cereals. Samples were taken in autumn using a combination of chemical expulsion and hand sorting of soil. The population was consistently larger on direct-drilled than on ploughed land, and the difference became greater in each successive year. Deep burrowing species were affected similarly to the population as a whole. Population differences on the two treatments were greater with spring — than autumn - sown crops. After tine cultivation numbers were usually similar to those after ploughing. On a direct-drilled clay soil on which straw had been either burned, or chopped and spread, no differences were recorded in the overall population. However, significantly larger numbers of deep burrowing species were found on the chopped and spread areas, whereas on the burned areas numbers of Allolobophora chlorotica were significantly greater.  相似文献   

13.
The influence of tillage methods on plant water status was measured in spring barley on a sandy loam soil (Wighill series) in 1976. Three methods of tillage were used: direct drilling, tine cultivation to 12.5 cm depth, and moldboard plowing to 20 cm depth. Soil bulk density was higher in the 0–5 and 5–10 cm layers of the direct-drilled plots. Soil strength was also higher in the direct-drilled plots to 22.8 cm depth compared with plowed plots, and to 15.2 cm depth compared wiht tine-cultivated plots. Thje only significant effect on soil water content (measured to 90 cm depth) was between 80 and 114 days from planting when extraction from the 0–10 cm depth was greater in the direct-drilled plots compared with the plowed plots, and at 20 cm depth greater in plowed plots than in direct-drilled plots. There were no significant differences between tillage methods in leaf water potential, above-ground dry matter produced, and grain yield.  相似文献   

14.
The release and fate of nitrogen from 15N-labelled perennial ryegrass (Lolium perenne L.) and white mustard (Sinapis alba L.) catch crops were studied in field microplots. The initial decline in 15N-labelled organic N, after incorporation of the material in early December, was more rapid from mustard containing 2.6% N than from ryegrass containing 1.4% N. After 9 months of decomposition, the residual organic 15N from the two materials declined at the same rate; the average decay constant for the following 2 years of decomposition was 0.30 a?1. After 33 months of decomposition, 23% and 34% of the mustard and ryegrass 15N, respectively, was recovered in organic residues in the topsoil. Seven per cent of the ryegrass N was leached below 45 cm in micro-lysimeters during the winter following incorporation. Three spring barley (Hordeum vulgare L.) crops, which succeeded ryegrass incorporation, accumulated 19%, 4% and 2%, respectively, of the ryegrass N in the above-ground plant parts. Perennial ryegrass swards recovered a total of 26% of the ryegrass and 22% of the mustard catch-crop N within 2 years. After 2 years of decomposition in unplanted soil, 82% of the ryegrass N was accounted for. The 15N that was not accounted for may be present in the 10–45 cm depth, or it may have been lost by denitrification.  相似文献   

15.
Compost maturity is one of several issues that the composting industry must face as it attempts to provide a high quality product to the agricultural community. In this paper, we examine the potential for using immature compost prepared from a mixture of municipal solid waste (MSW) and biosolids as a mulch for control of weeds in vegetable crop row-alleys. Two field experiments were conducted with 4 and 8-week-old composts in the fall of 1995 and the spring of 1996. The 4-week-old compost was applied to mulching depths of 3.8 (68 t dry weight .ha?1), 7.5 (135 t dry weight .ha?1), 11.3 (203 t dry weight .ha?1), and 15 cm (270 t dry weight .ha?1) in the fall, and at 2.0 (35 t dry weight .ha?1), 3.8, 7.5, and 11.3 cm depths in the spring. Other treatments were paraquat applied at 0.6 kg.ha?1 and an untreated control. All treatments were applied in row-alleys between raised, polyethylene-covered soil beds. The 8-week-old compost was applied to depths of 3.8, 7.5, 11.3, and 15 cm in fall and to depths of 2.0, 3.8, 7.5 and 11.3 cm in the spring. Untreated alleys served as controls. In the fall 1995 experiment under low weed pressures, the 4-week-old compost applied to 7.5 cm or greater depths completely inhibited weed germination and growth for 240 days after treatment. In the spring 1996 experiment, 4-week-old compost completely inhibited weed germination and growth for only 65 days if applied to a depth of 7.5 cm or deeper due to higher prevailing weed pressures, particularly due to yellow nutsedge (Cyperus esculentus L.). In the same spring experiment, a 50 % reduction in percentage weed cover was obtained for 240 days with a 11.25 cm deep layer of mulch compared to the control. In the fall 1995 experiment, 8-week-old compost applied at 7.5 cm or depths completely inhibited weed germination and growth for 240 days. In the spring 1996 experiment, 8-week-old compost applied as a 11.25 cm mulch reduced percent weed cover as compared to the control up to 240 days. In general, weed cover and weed dry weight decreased linearly as the depth of the mulch increased.Under these immature composts, inhibition of germination or subsequent weed growth may have been due to both the physical effects of the mulch and the concentrations of phytotoxic fatty acids during the first few days after mulches were applied. At the time of mulching with the 4-week old compost, acetic acid was present at a concentration of 1221 mg.kg?1 in the fall mulch, and at 4128 mg.kg?1 in the spring mulch. The same concentrations in the 8-week-old compost for the fall and spring mulches were 1118 mg.kg?1 and 3113 mg.kg?1, respectively. In conclusion, immature compost may provide an effective alternative weed control method for row-alleys in vegetable crop production systems. During these experiments, it was observed that man-made contaminants such as glass, hard and soft plastics in the composts were esthetically unacceptable and potentially posed hazards to field workers.  相似文献   

16.
The impact of urea prills (1–2 mm) versus urea supergranules (USGs, ～10 mm), placed at different depths, on the growth and nitrogen (N) use efficiency of spring wheat was investigated under greenhouse conditions. The amount of fertilizer 15N derived from either form was 50% greater in the top soil than at lower depths. The comparatively slower release and distribution of USG-N resulted in enhanced dry matter production and fertilizer-N uptake during the later growth stages that were also associated with a higher translocation of fertilizer-15N into the grain (34.9% versus 28.7% for the prills). Deeper placements of USGs (5.0–7.5 cm) resulted in greater fertilizer-N recovery in the crop (70.5–78.0%) compared to the use of prills (56.6%). Our results strongly suggest that the proper application of USGs can increase yields and fertilizer-N utilization of wheat and simultaneously decrease N losses compared to equivalent use of prills, and therefore presents important agronomic advantages.  相似文献   

17.
Arbuscular mycorrhizal fungi (AMF) can form symbiotic relationships with most crops, but their impact on the environmental migration of cadmium (Cd) in farmland is limited. A field experiment was performed in the rainy season (May–October) for two years in Cd-polluted farmland used for maize cultivation. A fungicide (benomyl) was used to specifically inhibit native AMF growth in the farmland. The growth and Cd uptake of maize and the Cd concentration and loss in runoff and interflow were investigated. Benomyl strongly and significantly inhibited AMF colonization rate in maize roots, reduced the contents of total and easily extractable glomalin-related soil protein (GRSP) in soil and the Cd uptake in maize roots, and increased the Cd uptake in shoots. Particulate Cd was the main form of Cd loss in runoff, while dissolved Cd was the main form of Cd leaching loss at depths of 20 cm and 40 cm. Inhibiting AMF increased the Cd concentration in runoff and interflow and promoted dissolved Cd loss in runoff and interflow at 20 cm depth by 34.7% and 68.0% and particulate Cd loss by 46.4% and 19.7%, respectively. Furthermore, the AMF colonization rate in maize roots and the GRSP content in soil were significantly positively correlated with Cd uptake in roots and negatively correlated with the concentration and loss of Cd in runoff and interflow. These results indicated that the benomyl-induced inhibition of native AMF promoted Cd transfer to maize shoots and increased Cd loss via runoff and interflow from polluted farmland.  相似文献   

18.
The characteristics and properties of the soil macropore system may cause different infiltration behavior under different tillage practices. To evaluate the effect of a specific tillage system on infiltration and percolation with particular regard to the influence of crop structure and soil animal activity dye tracer irrigation experiments were conducted in a silty (Luvisol) as well as in a sandy loam soil (Podzolluvisol). The spatial distribution of water flow paths was experimentally examined at four square areas of 0.49 m2, under conservation and conventional tillage. Natural rainstorms were simulated by irrigating the plots with 2.8×10−3 M methylene blue solutions. For both soils the root crowns of the agricultural crop, wormcasts and stained soil sections as well as macroscopic conduits were traced on plastic sheets. The investigated soil depths were 0, 5, 10 and 20 cm for the both soils. For the Luvisol, the 30, 40, 50, 80 and 120 cm depths were also studied.For the Luvisol, the conservation tillage plot revealed pronounced vertical connectivity and continuity of the macropore network (maximum depth of stained pores=120 cm), while at the conventional tillage plot, continuous macropores were observed to soil depths of 50 cm, but mainly restricted to the ploughed topsoil (0–30 cm soil depth).For the Podzolluvisol, at the conservation tillage site extensive mulch residues prevented water transport beneath 5 cm soil depth. In contrast, at the conventionally tilled site stained water reached a depth of 20 cm. For all investigated plots on both soil types, the location of the root crowns of agricultural crop and of wormcasts was not related to percolation patterns.The results suggest that conservation tillage on silty soils under agricultural landuse could induce an increased water retention capacity reducing the significance of fast runoff components.  相似文献   

19.
Improving phosphorus (P) accessibility in subsoils could be a key factor for sustainable crop management. This study aims to explain the quantity of different P fractions in subsoil and its biopore systems, and to test the hypothesis that crops with either fibrous (fescue) or tap‐root systems (lucerne and chicory) leave behind a characteristic P pattern in bulk subsoil, biopore linings and the rhizosphere. The crops were cultivated for up to 3 years in a randomized field experiment on a Haplic Luvisol developed from loess. Aqua regia‐extractable P (referred to as total P) and calcium acetate lactate‐extractable P (PCAL) were assessed at 0–30 (Ap horizon), 30–45 (E/B horizon), 45–75 and 75–105 cm subsoil depths. In addition, sequential P fractionation was performed on different soil compartments between 45 and 75 cm depths. The results showed that total P stocks below the Ap horizon (30–105 cm) amounted to 5.6 t ha?1, which was twice as large as in the Ap, although the Ap contained larger portions of PCAL. Both PCAL and sequential P extractions showed that biopore linings and the rhizosphere at the 45–75 cm depth were enriched, rather than depleted, in P. The content of inorganic P (81–90% of total P) increased in the following order: bulk soil = biopores <2 mm ≤ rhizosphere ≤ biopores >2 mm. Biopores >2 mm and rhizosphere soil were clearly enriched in resin‐ and NaHCO3‐extractable Pi and Po fractions. However, we failed to attribute these P distribution patterns to different crops, suggesting that major properties of biopore P originated from relict biopores, rather than being influenced by recent root systems. The stocks of the sum of these P fractions in the bulk subsoil (182 kg ha?1 at 45–75 cm depth) far exceeded those in the biopores (3.7 kg ha?1 in biopores >2 mm and 0.2 kg ha?1 in biopores <2 mm). Hence, these biopores may form attractive locations for root growth into the subsoil but are unlikely to sustain overall plant nutrition.  相似文献   

20.
Abstract. The objective of the present study was to investigate the potential of undersown catch crops to counteract soil degradation after autumn ploughing. Italian ryegrass (Lolium multiflorum Lam.) and white clover (Trifolium repens L.) were undersown in spring wheat on a loam soil in southern Norway, allowed to grow as cover crops after grain harvest and ploughed in to 20 cm depth as green manure in late October. Ryegrass prevented a collapse of the ridged plough furrow profile during winter, which occurred on grain monoculture and white-clover plots. Also, it tended to improve the water stability of aggregates, aggregate size distribution, bulk density, and pore volume in soil sampled in May. The preservation of the plough furrow profile was mainly attributed to enmeshment by an extensive system of fine roots and less to rhizosphere and microbial effects on aggregate stability. The results showed that ryegrass catch crops may give rapid structure improvements that are likely to contribute appreciably to easier seedbed preparation and less soil degradation in arable farming systems, even if the soil is ploughed in autumn.  相似文献   

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