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1.
A field laboratory was established in Prince Edward Island, Canada, to determine the effects of 2- and 3-year crop rotations, with conventional and minimum tillage treatments, on the severity of soilborne diseases of potato. The 2-year rotation consisted of spring barley and potato (cv. ‘Russet Burbank’), and the 3-year rotation was barley (undersown with red clover), red clover and potato. Examination of potato stem, stolon, and tuber tissues revealed significantly (P=0.05) lower levels of canker and black scurf caused by Rhizoctonia solani, in plants grown in 3-year vs. 2-year rotations. The severity of dry rot (Fusarium spp.) and silver scurf (Helminthosporium solani) was significantly (P=0.05) lower in tubers from plots managed with 3-year rotations and minimum tillage practices. Potato tubers harvested from 3-year rotational soils were significantly (P=0.05) less diseased than those from 2-year rotational soils following inoculation with Phytophthora erythroseptica, causal agent of pink rot. In greenhouse experiments using field soils from 2- and 3-year rotations, we found that potato plants growing in 3-year rotational soils were significantly (P=0.05) less diseased than those growing in 2-year rotational soils following inoculation with P. erythroseptica. Analysis of root zone bacteria recovered from the rhizosphere (exoroot) and potato root tissues (endoroot) showed that the greatest antibiosis activity inhibiting the growth of soilborne pathogens in vitro occurred in bacterial isolates recovered from the endoroot tissues of 3-year rotation crops under minimum tillage management. Our evidence supports the view that soil agroecosystems can be modified through rotation and conservation tillage practices to improve disease suppression by enhancing the antibiosis abilities of endophytic and root zone bacteria (endo- and exoroot). 相似文献
2.
Three tillage practices were compared on a subarctic silt-loam soil to evaluate whether conservation tillage could be used effectively to reduce soil losses from wind erosion without delaying crop maturity or reducing yield. Urea and ammonium nitrate were also compared as sources of fertilizer nitrogen. Plots were cropped to rapeseed (Brassica campestris L.) and barley (Hordeum vulgare L.) in a rapeseed-barley-fallow rotation and in continuous barley. Zero-tillage did not delay maturity nor did it result in reduced yields except where there was excessive competition from perennial grassy weeds. Neither placement appeared to be less than optimum in zero-tilled plots. With proper fertilizer placement and grassy-weed control, conservation tillage appears to be a viable method of reducing the potential for wind erosion in the subarctic. 相似文献
3.
Rotation and tillage effects on soil organic carbon sequestration in a typic Hapludalf in Southern Ontario 总被引：13，自引：0，他引：13
Increased use of conservation tillage is being considered as a way to sequester atmospheric C in the soil. However, little information exists on the effect of rotation and its interaction with tillage on soil organic carbon (SOC). A research trial with combinations of rotations and tillage treatments was sampled 20 years after its establishment to assess the effects on SOC sequestration in a typic Hapludalf in southern Ontario, Canada. The cropping treatments included continuous corn (zea mays L.), six rotations comprised of 2 years of corn following 2 years of another crop or crop sequence, and continuous alfalfa (Medicago sativa L.). Each rotation was split into either fall moldboard plow (MP) or fall chisel plow (CP) treatments. Continuous alfalfa was plowed and replanted every 4 years. Soil samples were taken incrementally to a depth of 40 cm and SOC and bulk density determined. The average SOC concentration (0–40 cm) was greatest in continuous alfalfa (18.0 g C kg−1). The treatments of soybean (Glycine max L.Merr.)+winterwheat (Triticum aestivum L.) or barley+barley (Trifolium pratense L.) (interseeded with red clover) followed by 2 years of corn had higher SOC concentrations (17.2–17.3 g C kg−1) than continuous corn and the treatments of 2 years of corn following 2 years of alfalfa or soybean (16.4–16.5 g C kg−1). The rotation of 2 years of barley followed by 2 years of corn had the lowest SOC concentrations (15.2 g C kg−1). On an equivalent mass basis, the rotations of soybean+winterwheat or barley+barley (underseeded with red clover) followed by 2 years of corn, had 2–9 Mg ha−1 more C than the other corn-based rotations. Including red clover in the winter wheat seemed to accelerate the rate of C mineralization compared to winter wheat without red clover; whereas interseeding red clover with barley increased SOC contents compared to excluding red clover in the barley rotation. More SOC was found in the top 10 cm and less in the 10–20 cm depth of the CP than in the MP soils. However, the CP did not increase the SOC content (0–20 cm) above that of MP indicating that this form of reduced tillage did not increase C sequestration in any of the rotations on this soil. 相似文献
4.
Double cropping of soybean has progressed less rapidly in the U.S. Southeastern Coastal Plains than expected by the ample rainfall and long frost-free season. Post-emergence herbicides, the management of plant residues to reduce water use by cover crops, and a no-till planter with a combination subsoiler are the innovations that have facilitated this new production. Full-season soybean (Glycine max L.) was planted following a grazed cover crop of winter rye (Secale cereale L.) or late-season soybean was planted following winter wheat harvest. In both cases, a special planter was used with an integral subsoil shank ahead of the opener. Full-season soybean under conservation tillage produced yields equal to or better than yields in conventional clean tillage. In a dry summer, soybean yields under conservation tillage exceeded conventional tillage because of suppressed early biomass production which conserved stored soil water and favored growth during the reproduction phase of the crop-cycle. Late-season soybean yields behind wheat favored the conservation tillage practice of in-row subsoil-planting into stubble. However, planting in burned-off wheat stubble produced the highest yields in this study. In a dry spring, the cover crop accelerated soil water use which resulted in lower soybean yields under conservation tillage. Comparisons of 76 vs. 97 cm row spacing were inconclusive, but the trend suggests that wider rows conserve water under periods of drought and that the narrower-row configuration favors adequate water regimes. 相似文献
5.
Tillage systems can influence weed seed viability and the distribution with depth of weed seeds in soil. To investigate this ‘tillage effect’, weed seed bank composition was determined at two soil depths (0–10 and 10–20 cm) in three tillage systems [mouldboard plough (MP), shallow tillage (ST), and direct drilling (DD)] established for 14 years on a sandy loam (Podzol) in Prince Edward Island, Atlantic Canada. The cropping system was a cool-season soybean (Glycine max L. Merr.) in rotation with barley (Hordeum vulgare L.). The objectives were to evaluate the size and composition of the viable soil seed bank, using the seedling germination method, and to determine if the adoption of non-inversion tillage practices (DD and ST) influence seed bank parameters relative to the conventional full inversion MP. The diversity of weed species was slightly lower for MP (17 species) compared to the ST (21 species) and DD treatments (22 species). The population for most weed species was relatively low with only three common species [low cudweed (Gnaphalium uliginosum L.), creeping buttercup (Ranunculus repens L.), common lambsquarters (Chenopodium album L.)] above 5 m−2. For the total soil depth sampled (0–20 cm), weed seed population was significantly greater under DD (56 weeds m−2) and ST (66 weeds m−2), compared to MP (25 weeds m−2), and mainly related to changes in the number of annual broadleaf weeds, compared to perennial broadleaf and grasses. Comparison of the 0–10 with the 10–20 cm soil depth showed a relatively uniform weed seed distribution for the MP treatment, while a greater proportion of weed seeds was found at the lower soil depth for DD and ST. This distribution tended to be weed species dependent. Soil texture and weed seed characteristics were considered to have a critical impact on the total weed seed bank size, specifically for the 10–20 cm soil depth. Overall, the weed bank size was relatively small indicating that adoption of conservation tillage practices for sandy loams in Atlantic Canada should not cause a major change in weed community and weed populations, or present a need for significant changes in weed control management. 相似文献
6.
Soil erosion continues to be a primary cause for soil degradation and the loss of soil quality throughout the world. Our objectives were to quantify soil erosion (referred to as erosional drift) and to assign erosion risk to six tillage and crop management treatments evaluated from 1995 to 1999 for a 5-year maize (Zea mays L.), soybean (Glycine hyspida L.), winter wheat (Triticum aestivum L.), oil-seed rape (Brassica napus var. oleifera L.), and spring barley (Hordeum vulgare L.) plus double-crop soybean rotation on Stagnic Luvisols in central Croatia. Standard black fallow (tilled, unsown, and without any vegetative cover) Universal Soil Loss Equation (USLE) plots were used to establish the erosion potential associated with the rainfall pattern for each year. Soil loss from the check plots was several times greater than the T value, which is estimated to be 10 t ha−1 per year. During the 2 years when spring seeded maize or soybean were grown (1995 and 1996) erosion risk was extremely high, especially for treatments where tillage and planting (row direction) were up and down the slope. When autumn seeded winter wheat or oil-seed rape were grown (1996/1997 or 1997/1998), soil erosion was insignificant. Also, except when plowing and sowing were up and down slope, erosion loss for the spring barley plus double-crop soybean crops in 1999 was insignificant. With no-tillage, soil erosion from the maize and soybean crops was reduced 40 and 65% compared to plowing up and down slope, even though the planting direction was still up and down the slope. With the exception of maize in 1995, erosion losses were moderate to insignificant when plowing and planting were performed across the slope. We conclude that erosion risk can be used as a reliable indicator of sustainable land management and that using no-tillage or plowing and planting perpendicular to the predominant slope are effective soil conservation practices for this region. 相似文献
7.
In the U.S. Southeastern Coastal Plains conservation tillage (CT) became useful as a management system with the development of in-row subsoiling systems capable of planting into heavy residues. Research priorities associated with the development of CT included: reducing cover crop water loss, improving stand establishment, assessing nutrient and water management requirements, determining optimal subsoiling strategies, understanding long-term conservation tillage effects on soil properties, evaluating the interaction of crop residue removal with tillage systems, and documenting tillage impact on pests and beneficial organisms. Since the late 1970s the Coastal Plains Soil and Water Conservation Research Center in Florence, SC has made a concerted effort to study these interactions and alleviate them as obstructions to the use of CT management. These studies showed that for Coastal Plain soils such as Norfolk sandy loam (fine-loamy, siliceous thermic, Typic Paleudults) winter cover crops such as rye (Secale cereale L.) desiccated the soil profile by evapotranspiration in the spring. This delayed emergence and early season growth of corn (Zea mays L.) but not full-season soybean (Glycine max (L.) Merr.). Conservation tillage helped manage soil strength by gradually increasing soil organic matter content, restricting traffic patterns and maintaining higher soil water contents. Laboratory studies demonstrated a negative correlation (R2=0.85) between proctor soil strength and organic matter content. Conservation tillage affected nematode, Bradyrhizobium japonicum and Heliothis species populations. Alternate cropping systems using rapeseed (Brassica napus L.) as a winter crop or sunflower (Helianthus annuus L.) either before soybean or after corn provided crop cover against potential soil loss from late autumn through early spring, when bare soil is exposed to intense rainfall. Water quality questions associated with CT have been raised but remain unanswered. Although CT can reduce runoff and erosion, the crop residues can support higher insect populations and pathogen inoculum levels, and thus prompt greater pesticide use. Quantifying relationships between soil strength, macropore formation and persistence, and water infiltration with surface and subsurface water quality is the focus of new long-term evaluations. The findings of these studies, published to date, are summarized in this paper. 相似文献
8.
Influence of tillage practices and nutrient management on crack parameters in a Vertisol of central India 总被引：5，自引：0，他引：5
K. K. Bandyopadhyay M. Mohanty D. K. Painuli A. K. Misra K. M. Hati K. G. Mandal P. K. Ghosh R. S. Chaudhary C. L. Acharya 《Soil & Tillage Research》2003,71(2):133-142
The frequency, size and rate of development of cracks influence the transport of water, nutrients and gases in the soil profile and plant growth processes in Vertisols. Despite their importance, studies on characterising cracks in Vertisols of India are limited. This study attempts to evaluate the influence of different tillage practices, nutrient management and cropping systems on cracking behaviour of a Vertisol in central India. The length, depth, width, area and volume of cracks were recorded after the harvest of the wet season crops, i.e. soybean (Glycine max L.) and rice (Oryza sativa L.) from three ongoing tillage experiments with three different cropping systems, i.e. soybean–wheat (Triticum aestivum L.), soybean–linseed (Linum usitatissimum L.) and rice–wheat. The results revealed that all the crack parameters were significantly negatively correlated with the water content of the 0–15 cm soil layer and, crack width and crack volume were significantly positively correlated with the bulk density of the 0–15 cm soil layer. Gravimetric water content and bulk density of the 0–15 cm soil layer together explained 79% variation in the crack volume. The crack volume was significantly negatively correlated (r=0.86,P=0.01) with the root length density of the previous soybean crop. Rice grown under puddled condition significantly enhanced different crack parameters viz., length, depth, width, surface area and volume of the cracks over nonpuddled direct seeded rice. Sub-soiling practised in soybean under the soybean–linseed system significantly reduced the width, depth, length and surface area of cracks by 12.5, 10, 5 and 12%, respectively, over conventional tillage. No tillage practised in soybean under soybean–wheat system resulted in significant increase in width, depth and volume of the cracks but decrease in length and surface area of cracks over conventional tillage and mould board tillage practice. Application of manure reduced the magnitude of different crack parameters in soybean–linseed cropping system. Thus cracking in Vertisols can be favourably managed by the selection of proper tillage practice, cropping system and organic manure amendments. 相似文献
9.
Wheat yield and weed population as influenced by three tillage systems on a clay soil in temperate continental climate 总被引：1，自引：0，他引：1
The potential benefits of conservation tillage practices depend mainly on the soil and climatic conditions of the site. A study was conducted to determine the effects of three tillage systems (conventional, CT; reduced, RT; zero, ZT) on spring wheat (Triticum aestivum L.) and weed growth on a clay soil in temperate continental climate, northern Alberta (55°43′N, 118°41′W), Canada. A medium duty cultivator with 25 cm sweeps spaced 22 cm apart and a working depth of 8–10 cm was used for tillage in the CT (once in fall and twice in spring) and RT (once in spring) plots. The ZT plots received a harrowing to spread straw and a preseeding application of Roundup (glyphosate) to control weeds. Experimental design was a randomized complete block with four replications and the tillage systems were fixed in space for the 1989, 1990 and 1991 seasons. The RT treatment resulted in higher yields than the CT or ZT treatments. However, the differences were not always significant. The ZT treatment produced higher yields than CT in 1989 and 1991, whereas its yields were lower than CT in 1990. The 3 year means of total dry matter (TDM) were 3899 kg ha−1, 3640 kg ha−1 and 3331 kg ha−1 for the RT, ZT and CT treatments, respectively. The corresponding grain yields were 1728 kg ha−1, 1573 kg ha−1 and 1530 kg ha−1. The concentration of total N in plants and grains of wheat, amounts of extractable NO3-N, NH4-N and P in soil and soil moisture and bulk density were not significantly affected by tillage. The mean weight diameter of aggregates in surface soil was significantly greater under ZT than under the other systems. Wild buckwheat (Polygonum convolvulus L.) was more abundant under CT, but common groundsel (Senecio vulgaris L.), dandelion (Taraxacum officinale Weber), hemp nettle (Galeopsis tetrahit L.), field horsetail (Equisetum arvense L.) and smartweed (Polygonum scabrum Moench) tended to have higher populations under the ZT system. The populations of foxtail barley (Hordeum jubatum L.) wild rose (Rosa sp.), stinkweed (Thlaspi arvense L.) and wild oats (Avena fatua L.) showed no consistent effect of tillage. Tillage or preseeding application of glyphosate did not provide an effective control of all weed species. The spring tillage of the RT system improved crop yields and weed control relative to ZT, whereas the fall tillage of the CT system (in addition to spring tillage) reduced crop yields and had no significant effect on weed population relative to RT. The overall results showed that tillage intensity could be reduced to the level of RT without any adverse influence on crop yields, soil properties or weed populations. The RT system is also economical and environmentally desirable owing to lower tillage and herbicide requirements. 相似文献
10.
Moisture conservation for rainfed wheat production with alternative mulches and conservation tillage in the hills of north-west India 总被引：3，自引：0，他引：3
In the hills of north–west India, maize (Zea mays L.)-wheat (Triticum aestivum L.) is the dominant cropping system. However, rainfed wheat suffers from lack of optimum moisture at sowing. Field experiments were conducted for 3 years on a silty clay loam (Typic Hapludalf) to evaluate the effectiveness of mulches and conservation tillage for rainfed wheat in mitigating this problem. The treatments were ten factorial combinations of five mulch-tillage practices and two nitrogen levels (N60 and N120 kg ha−1). Mulch treatments consisted of application of 10 Mg ha−1 (dry weight basis), to previous standing maize, of either wild sage (Lantana camara L.) or eupatorium (Eupatorium adenophorum Sprengel) in combination with either conventional or conservation (minium) tillage prior to wheat sowing. These alternative practices were compared to the conventional farmer practice of soil tillage after harvest of maize with no mulch. The application of these weed mulches to standing maize maintained friable soil structure owing to a five fold higher mean population of earthworms underneath mulch. Mulches resulted in 0.06–0.10 m3 m−3 higher moisture in the seed-zone when wheat was sown compared with the conventional farmer practice of soil tillage after maize harvest. Mulch-conservation tillage treatments favourably moderated the hydro-thermal regime for growing a wheat crop. The mean root mass density under these treatments at wheat flowering was higher by 1.27–1.40 times over the conventional farmer practice during the 3 year study. Conservation tillage holds promise because it does not require elaborate tillage and may ultimately reduce animal draught in the hilly regions. Recycling available organic materials having no fodder value coupled with conservation tillage may help enrich the soil environment in the long-term. The practice also offers gainful use of these obnoxious weeds that cause great menace in grass and forest lands in the region. 相似文献
11.
Recent research has indicated that conservation systems with narrow-rows have potential for higher crop productivity on southeastern USA Coastal Plains Soil. The objective of this study was to determine how surface tillage and subsoiling affect nutrient distribution in the soil profile in narrow- and wide-row systems. A secondary objective was to determine the effect of row position on soil pH and nutrient concentrations in the wide-row system. Soil samples were collected in 1996 from plots that had been growing soybean (Glycine max (L.) Merr.) double cropped with wheat (Tritiucum aestivum L.) for 3 years and then again in 1999 after 3 years of continuous corn (Zea mays L.). Narrow-row spacing was 19 cm for soybean and 38 cm for corn. Wide-row spacing was 76 cm for both soybean and corn. Wheat was grown in 19 cm wide-rows. Soil samples were randomly collected from throughout the plots in the narrow-row culture. In the wide-row culture, separate samples were collected from the row and from between rows. Treatments were surface tillage (disc tillage (DT) and no surface tillage (NT)), with different frequencies of subsoiling. The soil type was Goldsboro loamy sand (fine-loamy, siliceous, thermic, Aquic Kandiudult). Soil samples from four depths (the surface 5 cm of the A horizon, the remainder of the A horizon, the E horizon, and the top 7.5 cm of the B horizon) were analyzed for pH, P, K, Ca, and Mg. Nutrient concentrations and pH differed little between row spacings at any depth after either 3 or 6 years. Differences due to subsoiling appeared mainly due to nutrient removal as the treatments with more intense subsoiling had higher yield and lower concentrations of nutrients (except K). Concentrations of P, Mg, and Ca at the soil surface tended to be higher in NT than in DT, especially in the mid-rows of the 76 cm wide-row systems. The data suggest only small differences in soil nutrient stratification can be expected as growers adopt narrow-row crop production systems with intensive subsoiling. 相似文献
12.
During 1980, an extremely dry growing season, soybean (Glycine max L. Merrill) root morphologies were characterized at the R2 growth stage in Steele, Sharkey, Rilla, Calloway, and Stuttgart soils with a tillage pan and with a disrupted tillage pan. Results showed that the presence or absence of tillage pans resulted in dramatic changes in the soybean root morphology. Without pans, classical taproot systems tended to develop. With pans, soybean root systems tended to follow old root channels and fractures through the pan. Below the pan, soil structure manifested strong influences on root morphology. On all soils except the Steele (loamy sand), roots penetrated the tillage pan in numbers comparable to those penetrating the soil horizons with the pan disrupted. Although soil impedance to root penetration increases with drying and the 1980 growing season was exceptionally dry, mechanical impedance to soybean root penetration of tillage pans on silt loam and clay soils did not appear to be a problem. However, on the loamy sand soil mechanical impedance inhibited soybean root penetration and appeared to be a major problem. 相似文献
13.
Effects of mouldboard ploughing and direct planting on yield and nutrient uptake of potatoes in Norway 总被引：3，自引：0，他引：3
The use of conservation tillage systems is now widespread for cereals in erosion-prone areas of Norway. However, few growers are willing to adopt such practices for other crops. An experiment was conducted in southern Norway (60°46′N, 10°49′E) from 1987 to 1993 to compare the effects of two different tillage treatments on potato (Solanum tuberosum L.) yield and quality. The conventional labour-intensive treatment, with autumn mouldboard ploughing, levelling and two passes with a spring-tine harrow in spring was compared with planting directly into untilled barley (Hordeum vulgare L.) stubble, with straw removed. The soil type in the experiment was a morainic, stony loam (Typic Cryoboroll, Orthic Melanic Brunisol). Prior to the start of the experiment direct-planted plots had not been ploughed for 9 years. During the trial years (1987–1993) a pattern of two different yield curves emerged as functions of the date of harvesting. The yield curve for direct planting was steeper, crossing that of conventional tillage on approximately 10 September, thus predicting higher tuber yield for direct planting when harvesting occurred after this date, but lower tuber yield than with conventional tillage in the case of early harvesting. The reason for this is thought to be cooler soil and delayed growth and maturation with direct planting. Furthermore, direct planted potatoes gave higher haulm yield, and also had higher contents of N, P and K in both haulm and tubers. No significant differences in tuber quality were found between the two treatments. A strong negative correlation was found between the yield increase caused by direct planting and mean air temperature in August. The trial indicated that direct planting of potatoes in cereal stubble is a viable alternative to conventional plough tillage on loam soil in Norway, provided that the growing season is adequately long. 相似文献
14.
Temporal changes in the surface aggregate stability of an Oxic Paleustalf under different tillage practices (direct drilled/stubble retained versus conventional cultivated/stubble burnt) and under different crops (wheat (Triticum aestivum L.) versus lupin (Lupinus angustifolius L.)) were monitored at a 10-year-old rotation site in Wagga Wagga, N.S.W., Australia.
Seasonal fluctuations in aggregate stability were observed under all treatments and were greater than the differences detected between the different tillage and cropping treatments. The seasonal variation was significantly related to the soil water content at the time of sampling and the lowest stability occurred during the autumn/winter period. Cropping under direct drilling and stubble retention resulted in significantly higher stability and lower seasonal fluctuations in stability than under conventional tillage and stubble burning. Despite the seasonal fluctuation, water stability over the season of both of the macroaggregate (more than 250 μm) and microaggregate (less than 50 μm) fractions increased significantly.
While the mean (temporal) stability of the different treatments was significantly related to the mean organic carbon content (r = 0.91) and polysaccharide content, the temporal changes were not related to the soil organic carbon content nor the living root length density.
Lupin had a more beneficial effect on promoting macroaggregate stability than wheat under the conventional tillage/stubble burnt treatment but no significant difference was found under the direct drilled/stubble retained treatment. 相似文献
15.
Productivity parameters and soil health dynamics under long-term 2-year potato rotations in Atlantic Canada 总被引：1，自引：0，他引：1
M. R. Carter H. T. Kunelius J. B. Sanderson J. Kimpinski H. W. Platt M. A. Bolinder 《Soil & Tillage Research》2003,72(2):153-168
Crop rotation effects, due to emerging soil ecological interactions and processes that occur with time, can have a major impact on crop productivity and soil health. 2-year potato (Solanum tuberosum L.) rotation studies were conducted during an 11-year period on a fine sandy loam (Orthic Podzol) under a cool, humid climate in Prince Edward Island in eastern Canada. Rotation partners included Italian ryegrass (Lolium multiflorum Lam.), red clover (Trifolium pratense L.), and barley (Hordeum vulgare L.). The study objective was to assess trends in yield parameters, populations and diversity in nematodes and soil-borne pathogens, and soil structural stability and organic matter retention with time. Italian ryegrass had the largest biomass of both herbage (6.5 Mg ha−1) and roots (4.8 Mg ha−1), compared to red clover or barley. Averaged across 9 years, potato tuber yield was highest under Italian ryegrass (35.0 Mg ha−1) and lowest under red clover (31.1 Mg ha−1) rotations. Differences in tuber yield among rotations was associated with soil N limitation and nematode activity, but was not evident until Year 6. Population densities of specific plant parasitic nematodes recovered from roots and soil were generally low and varied according to host plant. Root lesion (Pratylenchus spp.) and root-knot (Meloidogyne spp.) nematodes were more prevalent under red clover compared to other rotational crops. Stunt (Merlinius spp. and Tylenchorhynchus spp.) nematodes were more common under Italian ryegrass. The main organisms associated with tuber-borne disease were Rhizoctonia solani, Streptomyces spp., Fusarium spp., and Helminthosporium solani. The greatest reduction in tuber-borne diseases occurred with the potato–red clover rotation but significant differences were infrequent. Soil structural form throughout the soil profile (to 30 cm depth) was not adversely affected by the rotational treatments during the duration of the study, while soil structural stability at the soil surface (0–10 cm) was significantly improved. Losses of soil organic C, during the 11-year period ranged from marginal (4%) for rotations with Italian ryegrass, to significant (16%) under the barley rotation. Computer simulations, using the Century model, illustrated the importance of C inputs to maintain soil organic matter levels. Overall, potato crop productivity and soil organic C were generally maintained in rotations that contained Italian ryegrass, but declined under rotations with red clover and barley. 相似文献
16.
The purpose of this work was to determine whether some soil physical and chemical properties, and microbial activity were affected by two conservation tillage systems in a Chernozemic clay loam soil (Vertic Argiudoll), after 5 years of trial initiation. Two crop sequences, corn (Zea mays L.)–wheat (Triticum aestivum L.)/soybean (Glycine max (L.) Merr.) and wheat/soybean, under chisel plowing (ChP) and no till (NT) were evaluated. Physical and chemical properties were also analyzed taking the same soil without disturbance as reference. The Hénin instability index (HI) was larger in ChP than in NT in both corn–wheat/soybean (C–W/S) and wheat/soybean (W/S) sequences (P≤0.05). The C–W/S sequence differed from W/S (P≤0.01) in total organic carbon (TOC). As regards organic carbon fractions, no differences were found in labile organic carbon (LOC), while W/S under ChP showed the lowest value (P≤0.01) of humified organic carbon (HOC). No differences were found in microbial respiration either in crop sequences or in tillage systems. Soil physical and chemical properties differentiated crop sequences and tillage treatments from the undisturbed soil when a Student’s t-test was performed. Five years elapsed since the beginning of this trial was time enough to detect changes in some of the soil properties as a consequence of management practices. An important reduction in the soil structural stability was observed as related to the undisturbed soil. However, the C–W/S sequence under NT resulted in lower soil degradation with respect to the other treatments. 相似文献
17.
J. P. Thompson 《Soil & Tillage Research》1992,22(3-4):323-337
In a long-term experiment on a vertisol in southern Queensland, depression of vegetative growth of barley (Hordeum vulgare L.) by stubble retention was far greater with zero tillage than with mechanical tillage of the fallow. The possible phytotoxic effects of stubble on barley and wheat (Triticum aestivum L.) were investigated in seedling bioassays. Stubble collected from field plots just prior to planting did not reduce germination of wheat or barley seed but markedly reduced coleoptile length at 4 days. This effect of stubble became less apparent after 6 and 8 days, and was overcome by increasing water volume in the bioassay dish. Stubble absorbed 4.5–6 times its own weight of water and thereby competed with the germinating seed. Filtrates of stubble macerates in water, collected either before or after incubation of the saturated stubble, had no effect on coleoptile length indicating the absence of a water-soluble phytotoxin.
Brown lesions on wheat coleoptiles (most apparent at 8 days) and roots were decreased by stubble but increased by more water in the bioassay dish. Alternaria sp. and two types of bacteria were associated with the coleoptile lesions, and Fusarium sp. and several types of bacteria were associated with root lesions. Surface sterilisation of seed reduced root lesions but not coleoptile lesions. Filtrates of both incubated and unincubated stubble macerates reduced coleoptile lesions.
Poor early growth of barley in the field on zero-till, stubble-retained plots was not associated with incorporation of stubble into the drill slit in contact with the seed. Poor early growth was not overcome by nitrogen fertilizer drilled into the soil 2 months before planting. The quantities of air-dried stubble on the soil surface were capable of absorbing of the order of 4 mm rainfall. It is concluded that neither phytotoxins nor water absorption by the stubble were likely causes of the problem of poor early growth. 相似文献
18.
Two different methods were evaluated for the assessment of Verucillium biguttatum in soil: the pellet sampler (PS) and the modified Andersen air sampler (AS). Both techniques allowed the distribution of soil on selective Rhizoctonia plates (RP) as soil fine particles and cylindrical pellets, respectively. The white speculating colonies of V. biguttatum can easily be recognized on RP.
Compared with the PS, the AS method yielded more colonies of V. biguttatum over a wider range of artificially-produced densities, and with a lower detection threshold. It is assumed that for germination and subsequent development of colonies a more or less close contact is essential. Microscopical observations revealed that the soil particles are often not in immediate contact with hyphae of R. solani and then no outgrowth of V. biguttatum can occur.
Combined with the AS, sampling the soil volumetrically with PS can serve as a more efficient substitute for the time-consuming weighing procedure.
The observed differences for various soils suggest that besides the presence of R. solani, more factors affect the germination process. The value of the AS method is discussed in view of its applicability to studies on population dynamics of V. biguttatum in soil. 相似文献
19.
Two field trials with spring barley (Hordeum vulgare L.) were conducted at two locations in Denmark in order to evaluate the effects of tillage and growth of a catch crop on yield parameters under temperate coastal climate conditions. Ploughing in autumn or spring in combination with perennial ryegrass (Lolium perenne L.) as a catch crop was evaluated on a coarse sand (Orthic Haplohumod) from 1987 to 1992 at three rates of N fertiliser application (60, 90 and 120 kg N ha−1 year−1). Rotovating and direct drilling were also included as additional tillage practices. The experiment was conducted on a 19-year-old field trial with continuous production of spring barley. Ploughing in autumn or spring in combination with stubble cultivation and a catch crop, in addition to minimum tillage, was evaluated in a newly established field trial on a sandy loam (Typic Agrudalf) from 1988 to 1992. Yield parameters and N concentrations in grain and straw were determined. On the coarse sand, N uptake in the grain in ploughed plots without a catch crop was significantly greater when spring ploughed as opposed to autumn ploughed, but grain and straw yields did not differ significantly. Grain yield, straw yield and total N uptake did not differ significantly between direct drilled and autumn ploughed plots, but the trend was for grain yield to be lower with direct drilling. After 19 years of catch crop use, yield parameters in ploughed plots were greater than in plots without catch crops. This was most pronounced in the autumn ploughed plots. Rotovating the catch crop in the spring decreased grain yield compared with underploughing the catch crop in autumn or spring. No significant interactions were found between tillage and N rates. On the sandy loam, grain as well as straw yield and total N uptake were not significantly affected by catch crop or time of ploughing. Grain yield was significantly lower with reduced tillage (stubble cultivation in autumn) than in all other treatments. 相似文献
20.
In order to identify the best management method for soybean [Glycine max (L.) Merr.] following barley (Hordeum vulgare L.), a field study was carried out at the Sari Agriculture College Station during two years. The experiment was conducted as a split–split plot design based on complete blocks with two methods of residue management (burning or non-burning of barley residue) as the main plot factor, three tillage methods (plow + disk, double disk and no-tillage) as sub-plot factor, and three within row plant spacings (4, 8 and 12 cm, with 50 cm row width) as sub-subplot factor. The experiment was performed in four replications and soybean cultivar Hill was used. The combined analysis of the data showed that the effect of tillage methods and spacing within rows on yield was significant at the 1% level of probability. No significant interaction among experimental factors was observed. Comparison of means (Duncan's multiple range test) indicated that yield means of plow + disk and double disk were significantly different (2371 and 2412 kg/ha, respectively) compared with no tillage (2115 kg/ha), but the difference between them was not significant. Yield means of 4 and 8 cm within row spacings (2452 and 2405 kg/ha, respectively) were significantly different compared to 12 cm spacing within the row (2041 kg/ha), but a significant difference between them was not observed. Results of this study showed that residue non-burning, plow + disk or double disk and 4 or 8 cm within-row-spacings are the best planting methods for soybean following barley. 相似文献