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1.
Soil degradation is the single most important threat to global food production and security. Wind and water erosion are the main forms of this degradation, and conservation tillage represents an effective method for controlling this problem. The objective of this study was to quantify the effects of three tillage methods [zero (ZT), minimum (MT) and conventional (CT)] and three four-year crop sequences [spring wheat (Triticum aestivum L.)–spring wheat–winter wheat–fallow; spring wheat–spring wheat–flax (Linum usitatissimum L.)–winter wheat; spring wheat–flax–winter wheat–field pea (Pisum sativum L.] on crop establishment, plant height, seed weight, soil water storage, crop water use, crop water use efficiency and grain yield over a 12-year period under Canadian growing conditions. Plant establishment was not adversely affected by tillage systems or crop sequences except for flax, where a small reduction was observed with ZT and MT. Conservation tillage showed a yield benefit over CT of 7%, 12.5% and 7.4% for field pea, flax and spring wheat grown on cereal stubble, respectively over the 12 years of the study. Much of the yield increase was due to an increase in soil water in the 0–30 cm soil layer with ZT and MT. However, tillage systems had no effect on grain yield for spring wheat grown on fallow and field pea stubble due to a lack of differences in spring soil water content. Flax grown in sequence with cereals only yielded higher than when it was grown in the sequence which included field pea, even though flax was seeded on spring wheat stubble in both cases. Winter wheat yielded higher when grown on flax stubble than on spring wheat stubble. The results indicate that a one-year non-cereal break crop was enough to alleviate the negative effects of consecutive cereal crops on winter wheat. Spring wheat grown on field pea stubble always yielded more than when grown on cereal stubble. A 10% increase in water use efficiency was observed with flax grown with ZT and MT management. Crop sequence improved water use efficiency in flax and spring wheat. Growing spring wheat on field pea stubble as opposed to growing it on cereal stubble resulted in a 10% increase in water use efficiency. Overall, rainfall accounted for 73%, 72%, 67% and 65% of total water used by field pea, flax, winter wheat and spring wheat, respectively. This explains the large year effect as a result of variation in growing (May–August) season precipitation. The non-significant tillage system by year interaction implies that the positive benefits of ZT and MT occur over a wide range of growing conditions, while the absence of a tillage system by crop sequence interaction suggests that knowledge developed under CT management also applies to ZT and MT. The results of this study support the large shifts towards in conservation tillage being observed in the Canadian prairies.  相似文献   

2.
Abstract. A five year field experiment was conducted to assess the influence of crop rotation and field pea residue incorporation into the soil on maize yield. The data indicated a 30% increase in maize yield grown in rotation with field pea compared to when it was grown after wheat and a further increase of 35% when field pea residues were incorporated into the soil. The effect of field pea and residue incorporation was greater in the presence of fertilizer nitrogen indicating the enhanced capacity of the crop to utilize N from the residue. Legume residue management in sub-tropical regions of the world, having coarse textured soils low in organic matter, could help to increase the yield of cereals besides saving some of the expensive fertilizer input.  相似文献   

3.
Nitrogen acquisition by field pea (Pisum sativum L.) and spring barley (Hordeum vulgare L.) grown on a sandy loam soil and availability of N in three subsequent sequences of a cropping system were studied in an outdoor pot experiment. The effect of crop residues on the N availability was evaluated using 15N-labelled residues. Field pea fixed 75% of its N requirement and the N2 fixation almost balanced the N removed with the seeds. The barley crop recovered 80% of the 15N-labelled fertilizer N supplied and the N in the barley grain corresponded to 80% of the fertilizer N taken up by the crop. The uptake of soil-derived N by a test crop (N catch crop) of white mustard (Sinapis alba L.) grown in the autumn was higher after pea than after barley. The N uptake in the test crop was reduced by 27% and 34% after pea and barley residue incorporation, respectively, probably due to N immobilization. The dry matter production and total N uptake of a spring barley crop following pea or barley, with a period of unplanted soil in the autumn/winter, were significantly higher after pea than after barley. The barley crop following pea and barley recovered 11% of the pea and 8% of the barley residue N. The pea and barley residue N recovered constituted only 2.5% and <1%, respectively, of total N in the N-fertilized barley. The total N uptake in a test crop of mustard grown in the second autumn following pea and barley cultivation was not significantly influenced by pre-precrop and residue treatment. In the short term, the incorporation of crop residues was not important in terms of contributing N to the subsequent crop compared to soil and fertilizer N sources, but residues improved the conservation of soil N in the autumn. In the long-term, crop residues are an important factor in maintaining soil fertility and supplying plant-available N via mineralization.  相似文献   

4.
Crop management practices are needed that increase crop residue groundcover and reduce soil erosion after winter wheat (Triticum aestivum L.) planting in the Palouse region of northern Idaho and eastern Washington. Trials were conducted in 1997 and 1998 at the University of Idaho Kambitsch Research Farm near Genesee, Idaho, using farm scale equipment to evaluate dry pea (Pisum sativum L. subsp. sativum) and lentil (Lens culinaris Medik) residue production and groundcover across cultivars and tillage intensity. After harvest, legume plot areas were prepared for winter wheat seeding using four main plot tillage systems designed to give progressive levels of tillage intensity: no-till (NT), Ripper–Shooter™ (RS), RS plus one cultivation, and RS plus two cultivations. In 1997, the two dry pea cultivars produced significantly greater residue than the lentil cultivars. In 1998, ‘Pro 2100’ dry pea had significantly higher residue production than ‘Columbian’ pea and ‘Crimson’ lentil cultivars. In 1997, initial residue cover was highest with NT, averaging 74% groundcover across legume cultivars. After winter wheat seeding, residue cover declined for all tillage treatments, but was still highest at 40% residue cover under NT. In 1998, residue cover was lower for all tillage treatments across all cultivars than in 1997, but NT still had the highest initial residue cover. Wheat yield was not affected by tillage or previous crop treatments in either year. This study showed that NT and reduced tillage systems can maintain previous crop residue on the surface for soil conservation and subsequent crop yields.  相似文献   

5.
Abstract

A three-year field experiment was conducted in Estonia to determine which combinations of pea (Pisum sativum L.) and wheat (Triticum aestivum L.), oats (Avena sativa L.) and barley (Hordeum distichon L.) were most suitable for mixed cultivation and the effect of pea on the yield potential of cereals. The inclusion of pea in cereal seeds and the increasing of its seed density led to substantial decreases in the grain yields of the cereal component. The reason for these decreases was the formation of smaller grains in cereals when intercropped with pea. The inclusion of pea in a cereal crop and the increasing of its seed density led to substantial increases in the protein content of the cereal grains. In barley and oats the increases in grain protein content were the lowest of the three cereals. At the same time, the maximum protein yield per area unit in cereals was obtained from plots of pure crops. In a mix with pea, the amounts of nitrogen consumed by cereals decreased and the protein yield of cereals per area unit were reduced in intercrops. Pea-cereal mixes had an advantage over cereal sole crops with regard to protein yield, due to the pea component. Pea-cereal mixes are particularly suitable for the conditions of organic farming, and should be recommended to farmers, as they ensure a relatively good harvest and high protein yield on soil without nitrogen fertilizers. In conclusion, the study showed that, of the three combinations, pea-oat mixed intercrops gave the highest yield of grain and protein yields.  相似文献   

6.
The effects of mouldboard ploughing, shallow tined cultivation and direct drilling on yields of winter wheat, barley, oats and oilseed rape were compared over 10 years. Three field experiments were conducted on two non-calcareous clays (stagnogleys) and a weakly structured silty soil (argillic brown earth). Two spring N levels were applied to the winter wheat plots on the clay soil in three years and to the winter barley plots on the silty soil in one year. This paper reports the soil bulk density and water content at sowing and the crop growth, yield components and yields obtained during the later years of the study: 1979–1984 on the clayey soils and 1981–1984 on the silty soil.

In the years when cereals were grown, differences in yield between cultivation treatments were small and inconsistent. Oilseed rape yielded significantly more after direct drilling than ploughing because of better establishment and uniformity of growth.

The success of continuous reduced tillage depended on both burning crop residues and good weed control.  相似文献   


7.
To promote conservation tillage in organic farming systems, weed control and ley removal within arable-ley rotations need to be optimized. A long-term field trial was thus established in Frick, Switzerland in 2002 on a clayey soil and with a mean precipitation of 1000 mm/year. The tillage experiment distinguished between conventional tillage with mouldboard ploughing (CT, 15 cm depth) and reduced tillage (RT), including a chisel plough (15 cm) and a stubble cleaner (5 cm). Results of a 2-year grass-clover ley (2006/2007) and silage maize (2008) are presented. Due to dry conditions, mean grass-clover yields were 25% higher in RT than in CT, indicating better water retention of RT soils. Clover cover and mineral contents of the fodder mixture were also higher in RT. The ley was successfully removed in autumn 2007 in RT plots, and a winter pea catch crop was sown before maize. In CT, ploughing took place in spring 2008. Maize yields were 34% higher in RT than in CT, despite a two- to three-fold higher but still tolerable weed infestation. Maize in RT plots benefited from an additional 61.5 kg of easily decomposable organic N/ha incorporated into the soil via the pea mulch. Measurement of arbuscular mycorrhizal colonization of maize roots indicated a similar mechanical disturbance of the topsoil through the reduced ley removal system compared with ploughing. It is suggested that RT is applicable in organic farming, even in arable-ley rotations, but long-term effects need further assessment.  相似文献   

8.
Nitrous oxide (N2O) emissions and biological nitrogen (N2) fixation by grain legumes are two major processes of N transformation in agroecosystems. However, the relationship between these two processes is not well understood. The objective of this study was to quantify N2O emissions associated with N2 fixation by grain legumes under controlled conditions. The denitrifying capability of two Rhizobium leguminosarum biovar viciae strains, 99A1 and RGP2, was tested in pure culture in the presence of nitrate and in symbiosis with lentil (Lens esculenta Moench) and pea (Pisum sativum L.), respectively, in sterile Leonard jars. Lentil and pea, either inoculated or N-fertilized, were grown in soil boxes under controlled conditions. Profile N2O concentration and surface N2O emissions were measured from soil–crop systems, and were compared with that of a cereal – spring wheat (Triticum aestivum L. ac. Barrie). Results indicated that: 1) neither R. leguminosarum strain, 99A1 or RGP2 was capable of denitrification in pure culture, nor in symbiosis with lentil and pea in sterile Leonard jars, suggesting that introducing these Rhizobium into soils through rhizobial inoculation onto lentil and pea will not increase denitrification or N2O emissions; 2) soil-emitted N2O from well-nodulated lentil and pea crops grown under controlled conditions was not significantly different than that from the check treatments, indicating that biological N2 fixation by lentil and pea was not a direct source of N2O emissions.  相似文献   

9.
Soil and crop management practices may alter the quantity, quality, and placement of plant residues that influence soil C and N fractions. We examined the effects of two tillage practices [conventional till (CT) and no-till (NT)] and five crop rotations [continuous spring wheat (Triticum aestivum L.) (CW), spring wheat–fallow (W–F), spring wheat–lentil (Lens culinaris Medic.) (W–L), spring wheat–spring wheat–fallow (W–W–F), and spring wheat–pea (Pisum sativum L.)–fallow (W–P–F)] on transient land previously under 10 years of Conservation Reserve Program (CRP) planting on the amount of plant biomass (stems + leaves) returned to the soil from 1998 to 2003 and soil C and N fractions within the surface 20 cm in March 2004. A continued CRP planting was also included as another treatment for comparing soil C and N fractions. The C and N fractions included soil organic C (SOC), soil total N (STN), microbial biomass C and N (MBC and MBN), potential C and N mineralization (PCM and PNM), and NH4-N and NO3-N contents. A field experiment was conducted in a mixture of Scobey clay loam (fine-loamy, mixed, Aridic Argiborolls) and Kevin clay loam (fine, montmorillonitic, Aridic Argiborolls) in Havre, MT, USA. Plant biomass yield varied by crop rotation and year and mean annualized biomass was 45–50% higher in CW and W–F than in W–L. The SOC and PCM were not influenced by treatments. The MBC at 0–5 cm was 26% higher in W–W–F than in W–F. The STN and NO3-N at 5–20 cm and PNM at 0–5 cm were 17–1206% higher in CT with W–L than in other treatments. Similarly, MBN at 0–5 cm was higher in CT with W–L than in other treatments, except in CT with W–F and W–P–F. Reduction in the length of fallow period increased MBC and MBN but the presence of legumes, such as lentil and pea, in the crop rotation increased soil N fractions. Six years of tillage and crop rotation had minor influence on soil C and N storage between croplands and CRP planting but large differences in active soil C and N fractions.  相似文献   

10.
Abstract. Field peas (Pisum sativum L.) were grown in sequence with winter wheat (Triticum aestivum L.) or spring barley (Hordeum vulgare L.) in large outdoor lysimeters. The pea crop was harvested either in a green immature state or at physiological maturity and residues returned to the lysimeters after pea harvest. After harvest of the pea crop in 1993, pea crop residues (pods and straw) were replaced with corresponding amounts of 15N‐labelled pea residues grown in an adjacent field plot. Reference lysimeters grew sequences of cereals (spring barley/spring barley and spring barley/winter wheat) with the straw removed. Leaching and crop offtake of 15N and total N were measured for the following two years. These treatments were tested on two soils: a coarse sand and a sandy loam. Nitrate concentrations were greatest in percolate from lysimeters with immature peas. Peas harvested at maturity also raised the nitrate concentrations above those recorded for continuous cereal growing. The cumulative nitrate loss was 9–12 g NO3‐N m–2 after immature peas and 5–7 g NO3‐N m–2 after mature peas. Autumn sown winter wheat did not significantly reduce leaching losses after field peas compared with spring sown barley. 15N derived from above‐ground pea residues accounted for 18–25% of the total nitrate leaching losses after immature peas and 12–17% after mature peas. When compared with leaching losses from the cereals, the extra leaching loss of N from roots and rhizodeposits of mature peas were estimated to be similar to losses of 15N from the above‐ground pea residues. Only winter wheat yield on the coarse sand was increased by a previous crop of peas compared to wheat following barley. Differences between barley grown after peas and after barley were not statistically significant. 15N lost by leaching in the first winter after incorporation accounted for 11–19% of 15N applied in immature pea residues and 10–15% of 15N in mature residues. Another 2–5% were lost in the second winter. The 15N recovery in the two crops succeeding the peas was 3–6% in the first crop and 1–3% in the second crop. The winter wheat did not significantly improve the utilization of 15N from the pea residues compared with spring barley.  相似文献   

11.
Abstract

Crop yield response to micronutrient fertilization is difficult to predict, particularly under unfavorable environmental conditions as these may alter both crop nutrient demand and the soil micronutrient supply to plant roots. The research objective was to evaluate the effect of various soil temperature and moisture conditions on crop growth response to added micronutrient copper (Cu), zinc (Zn), and boron (B) along with soil micronutrient supply and distribution among fractions. Brown and Dark Brown farm soils collected from southern Saskatchewan were used to grown wheat, pea and canola within controlled environment chambers. The biomass yields of all crops decreased under cold soil temperature and moisture stress (drought and saturated) conditions. Greater plant uptake of Cu, Zn, and B was associated with optimum (i.e., field capacity) soil moisture and warm temperature (23°C) growing conditions, compared to drought (i.e., 50% field capacity), saturated, and cold (5°C) temperature conditions. Environmental stress had the greatest impact on pea growth, reducing crop yield and micronutrient utilization efficiency more than 95%. Soil supplies of Cu and Zn were most negatively impacted by drought stress due to reduced mobility of these diffusion limited nutrients. The extractable micronutrients levels and chemical speciation fractions of Cu, Zn, and B indicating that bioavailability and micronutrient transformation were not affected during our short-term (i.e., six-weeks) study. However, it is suggested that assessments of micronutrient forms also be conducted on soil samples under actual moisture and temperature conditions as they exist in the experiment, as well as on dried, processed samples.  相似文献   

12.
Flexibility in crop rotation planning allows canola and pea producers to adapt to changing management practices and marketing opportunities. Current recommendations in western Canada are to follow a 1 in 4-yr rotation for canola or pea on a particular field, but producers are interested in increasing frequency of these crops. The objective of this study was to determine the impacts of frequency of broad-leaf crops canola and pea and fungicide application in various crop rotations on accumulation and distribution of nitrate nitrogen (N) and extractable phosphorus (P) in the soil profile after 8 yr on a Dark Brown Chernozem (Typic Boroll) loam at Scott, Saskatchewan. The field experiment (from 1998 and 2005) contained monoculture canola and monoculture pea compared with rotations that contained these crops every 2, 3, and 4 yr with wheat and/or flax. Two cultivars of canola were included, an herbicide-tolerant and blackleg-resistant hybrid, and a conventional (not herbicide tolerant) open-pollinated, blackleg-susceptible (OP) cultivar. Subplots were fungicide treatments that attempted to control both blackleg and sclerotinia stem rot in canola and mycosphaerella blight in pea. Residual soil nitrate N in most layers and extractable P in many layers were significantly affected by crop rotation or rotation length, with the greatest amounts after monocultures. Fungicide application resulted in decreased amount of residual soil nitrate N, but it had no effect on soil extractable P. Crop phase (i.e., individual crops that make up the rotation) had a significant effect on soil nitrate N in many crop rotations; for example, residual soil nitrate N tended to be greatest after pea or OP canola and also after flax in the 4-yr rotation with flax. Crop phase had no effect on soil extractable P in any crop rotation. The lower amounts of residual soil nitrate N were usually associated with greater cumulative seed yields, and more so with greater cumulative N removal in seed in various crop rotations and phases within rotations. In conclusion, the findings suggest that accumulation of residual nutrients in soil, especially nitrate N, can be minimized by extending crop rotations, using high-yielding disease-resistant canola cultivars, and applying fungicides in years with weather conditions conducive to diseases.  相似文献   

13.
In the Canadian prairies, current recommendations allow growing of canola or pea once every 4 years on a particular field to effectively mange diseases, insects, and weeds, but producers are interested in increasing frequency of these crops to optimize economic returns. A 4-year (from 1999 and 2002) field experiment, with treatments consisting of rotations of monoculture canola and pea to rotations that contained these crops every 2, 3, and 4 years with wheat and flax, was conducted on a Black Chernozem (Udic Boroll) silty clay at Melfort, Saskatchewan, to determine the impact of frequency of broad-leaf crops canola and pea in various crop rotations on accumulation and distribution of nitrate nitrogen (N) and extractable phosphorus (P) in the soil profile after 4 years. Two cultivars of canola, an herbicide-tolerant blackleg- resistant variety (hybrid) and a conventional (not herbicide tolerant) open-pollinated, blackleg-susceptible variety (OP), were included. Mean effects of crop rotation or rotation length on soil nitrate N were not significant, though the amount of soil nitrate N in different soil layers tended to be greatest with monocultures and least in the 4-year rotation with flax. Effects of crop phase (i.e., individual crops that make up the rotation)?×?crop rotation interactions on soil nitrate N were significant for all layers in the soil profile. The amounts of nitrate N in soil after canola, especially hybrid canola, were lowest in most crop rotations, suggesting the importance of canola in minimizing downward movement of nitrate N in the soil profile. Soil extractable P in the 0- to 15-cm layer was least with monocultures and greatest in the 4-year rotation with flax. There was a significant effect of crop phase on soil extractable P, but soil P levels varied with crop phase in different rotations. In conclusion, residual nitrate N in soil can be reduced by extending crop rotations and using high-yielding disease-resistant canola cultivars, most likely by improving crop yields.  相似文献   

14.
The aim of this investigation was to find the cause of poor growth of barley that occurred with zero tillage and stubble retention in a long-term fallow management experiment on a vertisol in southern Queensland. The experiment compares 12 treatments comprising three factors of tillage (zero, mechanical), stubble (burnt, retained) and nitrogen fertilizer (0, 23 and 46 kg ha−1 year−1) in four randomised blocks. Dry matter yield of barley at anthesis showed a highly significant Mitscherlich relationship with tissue nitrogen (N) concentration. Cate-Nelson analysis indicated a critical N concentration of 1.58%N. The barley responded to fertilizer N although 9 of 12 zero-till, stubble-retained plots and 5 of 12 mechanical-till, stubble-retained plots still lay below the critical N concentration. Zero-till, stubble-retained treatment had least nitrate-N in the soil profile to 120 cm indicating a problem in N supply rather than in N recovery by the roots.

The effects of the long-term treatments on properties related to the N supplying capacity of the soil were investigated by determinations on topsoil samples from which undecomposed stubble was removed. Soil from zero-till, stubble-retained treatment had more organic carbon (C) and Kjeldahl N than mechanical-till, stubble-retained treatment which had more than stubble-burnt treatments. The C:N ratio of the soil was lower in stubble retained treatments. Kjeldahl N was higher with annual N fertilization only where stubble was retained. Organic C increased and Kjeldahl N decreased over a 3 year period in all treatments. Respiration of CO2, mineralizable N, and microbial biomass C and N in the soil were all greater with long-term stubble retention than with stubble burning irrespective of tillage treatment.

Numbers of root-lesion nematodes (Pratylenchus thornei Sher and Allen) and stunt nematode (Merlinius brevidens (Allen) Siddiqi) following a wheat crop were substantially greater with zero-till than with mechanical-till. Root-lesion nematode were increased by N fertilization of previous crops while stunt nematodes were increased by stubble-retention. Earthworm numbers were increased by stubble retention particularly when combined with zero tillage.

Factors responsible for observed differences in soil nitrate and crop response to N in this field experiment appear to be: (a) N immobilization by recently retained stubble, (b) lower rates of mineralization of soil N under surface-retained stubble, and (c) higher rates of leaching in zero-till treatment.  相似文献   


15.
Abstract

A two-year field experiment was conducted to investigate the impact of short crop rotation and organic amendments on rapeseed yield under weed competition conditions. The primary experimental plots consisted of either triticale or pea as a prior crop, consisting of four subplots with either 25 tons of composted cattle manure (CCM), 150?kg urea N ha?1 (N), 25 tons composted cattle manure + 75?kg urea N ha?1 (CCM?+?N), or no urea N or manure added as the control (C0). Rapeseed seed yield was not significantly affected by previous crops, except for rapeseed grown after pea which had slightly higher seed yield (2058?kg ha?1) than those grown after triticale (1942?kg ha?1). Plants that received CCM?+?N produced the highest amount of seed yield (2447?kg ha?1), but were not significantly different from plants that received just urea N (2218?kg ha?1). Weeds gained more biomass when the previous crop was pea compared to those whose previous crop was triticale. Weeds in plots that received CCM?+?N produced the greatest biomass, followed by N, and CCM plots, respectively.  相似文献   

16.
Crop rotation and cultural practice may influence soil residual N available for environmental loss due to crop N uptake and N immobilization. We evaluated the effects of stacked vs . alternate‐year crop rotations and cultural practices on soil residual N (NH4‐N and NO3‐N contents) at the 0–125 cm depth, annualized crop N uptake, and N balance from 2005 to 2011 in the northern Great Plains, USA. Stacked rotations were durum (Triticum turgidum L.)–durum–canola (Brassica napus L.)–pea (Pisum sativum L.) (DDCP) and durum–durum–flax (Linum usitatissimum L.)–pea (DDFP). Alternate‐year rotations were durum–canola–durum–pea (DCDP) and durum–flax–durum–pea (DFDP). Both of these are legume‐based rotations because they contain legume (pea) in the crop rotation. A continuous durum (CD) was also included for comparison. Cultural practices were traditional (conventional tillage, recommended seeding rate, broadcast N fertilization, and reduced stubble height) and improved (no‐tillage, increased seeding rate, banded N fertilization, and increased stubble height) systems. The amount of N fertilizer applied to each crop in the rotation was adjusted to soil NO3‐N content to a depth of 60 cm observed in the autumn of the previous year. Compared with other crop rotations, annualized crop biomass N was greater with DCDP and DDCP in 2007 and 2009, but was greater with DDFP than DCDP in 2011. Annualized grain N was greater with DCDP than CD, DFDP, and DDFP and greater in the improved than the traditional practice in 2010 and 2011. Soil NH4‐N content was greater with CD than other crop rotations in the traditional practice at 0–5 cm, but was greater with DDCP than CD and DDFP in the improved practice at 50–88 cm. Soil NO3‐N content was greater with CD than other crop rotations at 5–10 cm, but was greater with CD and DFDP than DCDP and DDCP at 10–20, 88–125, and 0–125 cm. Nitrate‐N content at 88–125 and 0–125 cm was also greater in the traditional than the improved practice. Nitrogen balance based on the difference between N inputs and outputs was greater with crop rotations than CD. Increased N fertilization rate increased soil residual N with CD, but legume N fixation increased N balance with crop rotations. Legume‐based crop rotations (all rotations except CD) reduced N input and soil residual N available for environmental loss, especially in the improved practice, by increasing crop N uptake and N immobilization compared with non‐legume monocrop.  相似文献   

17.
This study was undertaken to ascertain whether pulses, instead of pasture legumes, were more beneficial to grain yields by the following cereals in ley rotation systems. We evaluated growth processes for pastures or pulses and growth and yields for the following sequential crops of wheat and barley in a 3-crop rotation. The pasture or pulse phase that formed the main treatments consisted of grass pastures (Grass), medics (Medic) or faba beans that was either green manured (Faba-gm) or harvested for grain (Faba-gr). The rotations were initiated in two phases with Phase 1 starting in 1994 and Phase 2 in 1995, and each phase ran over 2 rotation cycles lasting 6 years. Despite differences in dry matter (DM) produced in the shoots and roots by the pastures and faba beans in the first years, they had similar seasonal evapotranspiration (ET) so water stored in the 100 cm profile of the soil was always similar when wheat was planted. By contrast, inorganic N in soil at wheat planting was always higher in legume rotations than in Grass and these differences persisted to the barley crop. Cereals in rotations with faba beans (Faba-gr and Faba-gm) produced more DM and grains than in Grass. In only 2 out of 8 croppings of cereals did wheat or barley in Medic out-yield those in Grass. These yield differences were not associated with uptake of soil N or use of soil-water by the cereals, but possibly due to lower levels of Pratylenchus neglectus in the soil under rotations with faba beans compared with pasture. Increased N supply after legumes or from fertilizer, however, increased grain protein in the cereals. This study showed that rotations with faba beans produced higher yields for the following cereals than with grassy or legume pastures, also green manuring of faba beans produced no advantage in yield for the cereals.  相似文献   

18.
Field pea (Pisum sativum L.) is widely grown in South Australia (SA), often without inoculation with commercial rhizobia. To establish if symbiotic factors are limiting the growth of field pea we examined the size, symbiotic effectiveness and diversity of populations of field pea rhizobia (Rhizobium leguminosarum bv. viciae) that have become naturalised in South Australian soils and nodulate many pea crops. Most probable number plant infection tests on 33 soils showed that R. l. bv. viciae populations ranged from undetectable (six soils) to 32×103 rhizobia g−1 of dry soil. Twenty-four of the 33 soils contained more than 100 rhizobia g−1 soil. Three of the six soils in which no R. l. bv. viciae were detected had not grown a host legume (field pea, faba bean, vetch or lentil). For soils that had grown a host legume, there was no correlation between the size of R. l. bv. viciae populations and either the time since a host legume had been grown or any measured soil factor (pH, inorganic N and organic C). In glasshouse experiments, inoculation of the field pea cultivar Parafield with the commercial Rhizobium strain SU303 resulted in a highly effective symbiosis. The SU303 treatment produced as much shoot dry weight as the mineral N treatment and more than 2.9 times the shoot dry weight of the uninoculated treatment. Twenty-two of the 33 naturalised populations of rhizobia (applied to pea plants as soil suspensions) produced prompt and abundant nodulation. These symbioses were generally effective at N2 fixation, with shoot dry weight ranging from 98% (soil 21) down to 61% (soil 30) of the SU303 treatment, the least effective population of rhizobia still producing nearly double the growth of the uninoculated treatment. Low shoot dry weights resulting from most of the remaining soil treatments were associated with delayed or erratic nodulation caused by low numbers of rhizobia. Random amplified polymorphic DNA (RAPD) polymerase chain reaction (PCR) fingerprinting of 70 rhizobial isolates recovered from five of the 33 soils (14 isolates from each soil) showed that naturalised populations were composed of multiple (5-9) strain types. There was little evidence of strain dominance, with a single strain type occupying more than 30% of trap host nodules in only two of the five populations. Cluster analysis of RAPD PCR banding patterns showed that strain types in naturalised populations were not closely related to the current commercial inoculant strain for field pea (SU303, ≥75% dissimilarity), six previous field pea inoculant strains (≥55% dissimilarity) or a former commercial inoculant strain for faba bean (WSM1274, ≥66% dissimilarity). Two of the most closely related strain types (≤15% dissimilarity) were found at widely separate locations in SA and may have potential as commercial inoculant strains. Given the size and diversity of the naturalised pea rhizobia populations in SA soils and their relative effectiveness, it is unlikely that inoculation with a commercial strain of rhizobia will improve N2 fixation in field pea crops, unless the number of rhizobia in the soil is very low or absent (e.g. where a legume host has not been previously grown and for three soils from western Eyre Peninsula). The general effectiveness of the pea rhizobia populations also indicates that reduced N2 fixation is unlikely to be the major cause of the declining field pea yields observed in recent times.  相似文献   

19.
为了探讨不同覆盖耕作方式对农田土壤物理性状及作物产量的影响,该试验研究了免耕、常规2种耕作方式和4种留茬高度的玉米秸秆还田处理,对麦-玉两熟农田土壤含水率、容重、孔隙度以及作物产量的影响。结果表明:在0～40cm土层内,秸秆还田的集雨和保水效果显著,免耕留茬0.5m还田处理的含水率比免耕无覆盖处理增加了15.95%。秸秆还田量对0～40cm内土壤贮水量的影响不同。耕作措施显著影响了土壤容重,小麦播种前常规留茬1m还田、常规全量还田处理容重低至1.0g/cm3左右。秸秆还田能增加土壤总孔隙度、降低毛管与非毛管孔隙度的比值。单一免耕处理降低了作物产量,而免耕覆盖能增产,其留茬1m还田处理比无还田处理增产22.44%,比常规留茬0.5m还田处理高3.64%。因此,免耕留茬1m还田处理在改善农田土壤物理性状和增加作物产量方面显著,该研究可为农田管理过程中耕作措施和秸秆还田量的选择提供参考依据。  相似文献   

20.
Intercropping is of increasing interest in temperate-arable farming systems. The influence of nitrogen (N) fertilization and sowing ratio on concentrations and uptake of calcium (Ca), potassium (K), magnesium (Mg) and phosphorus (P) by oat and pea was assessed in three substitutive intercrops on a fertile soil in eastern Austria. N decreased Ca in oat grain and increased P in pea grain as well as Ca and Mg in oat residue and Mg and P in pea residue. Intercropping did not affect nutrient concentrations of oat grain, whereas a lower pea share in intercrops increased P in pea grain. In residue, Ca, K and Mg concentrations were higher in oat and Ca and K partly lower in pea with a lower share of each crop. The oat-dominated intercrops could partly achieve a slightly higher total grain nutrient yield than pure stands at no or low N; however, these benefits diminished with a higher pea share and N input. In comparison to pure stands, higher residue nutrient yields were obtained by intercropping in all sowing ratios and fertilization levels. Consequently, oat–pea intercropping can be a strategy for increasing the macronutrient yield of grain and especially of residue for ruminant feeding.  相似文献   

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