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1.
S. Yücel 《Crop Protection》1995,14(8):653-655
Field trials conducted in the pepper growing area ( çel/Turkey) showed that solarization alone and combined with a reduced dose of methyl bromide (40 g/m2), were effective in controlling crown blight disease caused by Phytophthora capsici. Solarization was achieved by covering plots with a clear polyethylene sheet, 0.03 mm thick for 8 weeks. The temperature reached 47 °C and 35 °C at 5 cm and 30 cm soil depth, respectively, an average of 3–8 °C higher than those at equivalent depths in the untreated plots. The average incidence of the disease in solarization plus a reduced dose of methyl bromide, the recommended dose of methyl bromide, solarized and untreated plots in 1991 and 1992 were 17.6 and 13.3%; 20.8 and 16.8%; 24.1 and 19.7%; 39.8 and 42.9%, respectively. All treatments significantly reduced disease incidence.  相似文献   

2.
The effects of relative humidity (RH) and temperature on tomato powdery mildew (Leveillula taurica) were studied in controlled environments to define conditions that affect disease development in fresh market tomatoes in California. Gradients of RH (20–90%) at constant temperatures (20–30°C) were generated in single growth chambers to determine their effect on mildew development on mature tomato plants. Temperatures of 30°C and above were deleterious for spore germination, germ tube elongation, and disease development. Lesion growth and rate of disease progress were significantly higher at 20°C than at 25°C. Low RH levels (20–40%) reduced spore germination and lesion growth, accelerated host tissue death and reduced disease progress. Intermediate RH levels (50–70%) increased spore germination and optimized disease development, provided temperatures were maintained within favorable limits. High RH levels (80–90%) were favorable for spore germination but continued exposure to these conditions led to a limited lesion growth and disease progress. Short daily periods (two or three daily exposures of at least 2 h) of high temperatures (35°C) suppressed disease development by 70–92%.  相似文献   

3.
The genus Lesquerella is a promising source of hydroxy fatty acids (HFA). Several species such as Lesquerella fendleri and Lesquerella mendocina are candidate crops for arid and semi-arid cropping systems. Several reports are available on the environmental effects on growth and yield in Lesquerella, but information on the effect of temperature on plant growth and development specifically during the reproductive period in Lesquerella is limited. The objective of this work was to determine the effect of two contrasting thermal regimes after flowering on time to maturity, plant growth and biomass allocation to the different organs in L. fendleri and L. mendocina. A greenhouse experiment was conducted with plants grown at a range of 11–23 °C during the vegetative phase. After this stage, 50% of the plants of each species remained under the same temperature regime until maturity, whereas the other 50% was transferred to another module subjected to a range of 17–31 °C until maturity. The duration of the reproductive phase was reduced by 23 days in plants of both species in the 17–31 °C treatment compared to those at 11–23 °C, although no differences were observed when the length of the reproductive phase was measured in thermal-time units. Total plant biomass for both species was 20% greater in the 11–23 °C treatment. In L. fendleri, this increment occurred due to more vegetative shoot biomass, whereas in L. mendocina it was associated with greater reproductive and root biomass. No changes in biomass allocation were produced by temperature in L. fendleri, while in L. mendocina the lower temperature regime increased allocation to the reproductive organs, at the expense of a lower allocation to vegetative shoot. These results could be used to predict the specific temperature effects after flowering on yield under field conditions, and suggest that L. mendocina might be a promising perennial alternative for cooler sites.  相似文献   

4.
A 3 years field trial examined the effect of newly and previously applied lime on the growth and yield of two near-isogenic wheat genotypes differing only in aluminium (Al) tolerance (Triticum aestivum L. Al-sensitive line ES8 and Al-tolerant line ET8), and barley (Hordeum vulgare cv. Mundak) on an acid soil (pHCaCl2 4.6 in 0–10 cm and pH 4.1–4.3 in 10–40 cm) in the medium rainfall region of Western Australia. The trial consisted of four lime treatments: (i) no lime control; (ii) surface liming at 1.5 t ha−1 in 1999; (iii) surface liming at 2.5 t ha−1 in 1984; (iv) liming in 1984 and re-liming in 1999. Wheat crops were grown in 1999 and 2001, and barley was grown in 2000.

Liming in 1984 increased the pH in both topsoil and subsoil and decreased toxic Al in the subsoil. Liming in 1999 largely increased soil pH in the 0–10 cm in previously unlimed and limed plots, but only slightly increased the pH in 10–20 cm 2 years after application. In 1999, there was an overall 14% grain yield increase by growing ET8, mostly due to much better performance (41%) of ET8 over ES8 in the treatment with surface liming in 1999. In 2001, ET8 had yield 24% higher in the no lime control and 14% higher in the treatment with liming in 1999 compared with ES8. While both genotypes had similar root length density in the topsoil, root length density in acid subsoil was 22–160% higher for ET8 than for ES8. Wheat genotypes produced 23–24% higher yield due to the liming in 1984 compared to the no lime control. In 2000 season, shoot biomass of barley increased by 45–70% in the limed treatments compared with the no lime control. Liming at 2.5 t ha−1 in 1984 or liming at 1.5 t ha−1 in 1999 increased yield by 25%. Liming in 1984 and re-liming in 1999 increased the yield by over 50%. The results suggest that surface liming can ameliorate subsoil acidity as measured 15–17 years after application, and that growing an Al-tolerant crop in combination with surface liming provides a good strategy to combat subsoil acidity. The genotypic variation in response to liming appears to result from the difference in the sensitivity of root proliferation to low pH and high Al.  相似文献   


5.
Rice (Oryza sativa L.) followed by chickpea (Cicer arietinum L.) or a fallow is one of the predominant cropping systems in the rainfed lowlands of India. Crop rotation experiments over 3 years (1996–1998) to quantify N supply and demand under rainfed lowland rice–chickpea and rice–fallow cropping systems on a loam Alfisol and a clay Vertisol in Raipur, India were conducted under direct-seeded rice culture. The rice growth, yield, development and N accumulation were affected most by N rates (0, 40, 80, 120 kg ha−1) followed by cropping system (rice–chickpea, rice–fallow) and soil types (Alfisol, Vertisol). The incorporation of chickpea in the cropping system helped in accumulating a greater amount of soil N than fallow. The rice yield, dry matter and N accumulated were significantly higher in rice–chickpea than rice–fallow systems on both soils and in all years. The lowest rice yields were recorded in 1997 due to unfavorable rainfall distribution. The total rainfall was the highest in this season, but most of it occurred during a short period at an early growth stage. The post-heading rains were lowest in this season and resulted in the lower rice yield as compared with that of 1996 and 1998. This indicates the significance of rainfall distribution in controlling yield in a rainfed environment. The rice yields were lower on Vertisol than Alfisol during periods of drought. The performance of chickpea was also better in Alfisol as compared with that in the Vertisol due to its better soil physical attributes. The residual effect of N applied to the preceding rice crop was non-significant on all yield, growth and N accumulation parameters of chickpea. The N balance computed from the top 70 cm soil layers indicated less N loss in the rice–chickpea system as compared with that in rice–fallow. The recovery efficiency at the highest N rate (120 kg N ha−1) was higher for the rice–chickpea (57–61%) than that of rice–fallow (49–53%) system. The improved N balance for rice–chickpea system from third year onwards was due to switch to dry seeding and improved soil N status. The inclusion of legume and the effective capture of biologically fixed N and soil N through direct-seeded rice system in rainfed lowlands may help in improving the rice yield of resource poor farmers.  相似文献   

6.
Field experiments were conducted in the 2002/2003 and 2003/2004 dry seasons at the Irrigation Research Station of the Institute for Agricultural Research, Kadawa (11°39′N, 38°02′E, 500 m above sea level) in the Sudan Savanna Ecological Zone, Nigeria to study the effects of oxadiazon, date of planting and intra-row spacing on yields of garlic (Allium sativum L.) under irrigation at Kadawa, Nigeria. A uniform inter-row spacing of 15 cm was maintained in the two seasons. The results obtained showed that the hoe-weeded plots and application of oxadiazon at 1.5 and 2.0 kg a.i./ha resulted in comparable but significantly higher bulb yield per hectare, bulb diameter, bulb weight and number of cloves than oxadiazon at l.0 kg a.i./ha and unweeded check. Bulb yield per hectare, bulb diameter, bulb weight and number of cloves were higher at early November planting. Planting garlic at 5 cm intra-row spacing resulted in higher bulb yield in both seasons.  相似文献   

7.
The many recent dry-grind plants that convert corn to ethanol are a potential source of substantial amounts of corn oil, if an economical method of separating it can be developed. Oil separation from corn germ by aqueous extraction (AE) was studied. Batches of 5–20% germ in a buffer solution were preheated in a pressure cooker, ground in a blender or colloid mill, churned in an incubator/shaker and centrifuged to separate a free oil fraction. The highest oil yields were obtained when the germ mass fraction was between 0.1 and 0.16. Addition of an enzyme solution to the ground germ suspension prior to churning, aqueous enzymatic extraction (AEE) gave an oil yield twice as high as the AE yield, carried out using similar conditions. Both types of extraction produced the most oil after a 122 °C cook followed by churning at 160 rpm and 70 °C. Oil yield increased linearly with dispersion loading, from 0.5 up to 1.0 g/cm2 based on beaker cross-section (0.09–0.12 germ mass fraction). Over a several month period the germ used for the extractions became more difficult to extract, despite storage at 4 °C.  相似文献   

8.
In high productivity zones of Indo-Gangetic Plains in south Asia, the rice–wheat system is stressed due to production fatigue as evidenced by declining soil organic matter content, low efficiency of fertilizer use and diminishing rates of factor productivity. We, therefore, conducted field experiments at Modipuram, India, to conserve soil organic carbon, improve N and P use efficiency, and increase yields of rice–wheat system through inclusion of forage cowpea during the summer before cultivating the rice–wheat system. Cowpea forage harvested at 50 days removed greater amounts of N and P through aboveground biomass than those recycled through belowground roots and nodules. The NO3-N in soil profile below 45 cm depth after wheat harvest was greater under fallow during summer than under cowpea, suggesting that cowpea minimized NO3-N leaching beyond 45 cm depth. Similarly, in the treatments receiving both 120 kg N and 26 kg P ha−1, NO3-N in soil below 45 cm depth was lower compared to those receiving N or P alone. After three crop cycles, soil OC content in 0–15 and 15–30 cm depths was greater compared to initial OC in plots having cowpea. P applied at 26 kg ha−1 increased available P content over initial P content, and also over P content of soil under no P treatments. The available P content was, however, invariably low under summer cowpea plots as compared to that under no cowpea ones. With continuous rice–wheat cropping, the bulk density (BD) of soil increased over the initial BD at different profile-depths, more so at 30–45 cm depth in no cowpea plots, but inclusion of summer cowpea helped decreasing the BD in the surface (0–15 cm) and sub-surface (15–30 and 30–45 cm) soil layers. Summer cowpea grown on residual fertility after wheat harvest did not influence rice yield, but increased wheat grain yield (P<0.05 during the terminal year), when both the crops received fertilizer N and P at recommended rates. Skipping of N or P or both, however, resulted in consistently low yield of these crops under summer cowpea treatments than those under no cowpea treatments, although the differences were not necessarily significant every year. The use efficiency of applied N and P fertilizers in rice and wheat, measured as agronomic efficiency and apparent recovery, was increased with the use of fertilizer N and P at recommended rates, and also with inclusion of summer cowpea.  相似文献   

9.
Production of spring potato (Solanum tuberosum L. cv. Désirée) on a deep sandy soil in the central highland of the Negev desert of Israel under drip irrigation with saline water (up to 6.2 dS m−1) was studied in the years 1992–1997. The objective of the study was to determine the effects of saline water irrigation on potato production in an arid environment with special focus on the interactions with weather conditions. Although yields were often high, salinity effects were evident in some years. Thus 1992 and 1996 yields were 6–7 kg m−2 and showed no significant effect of salinity, while a pronounced drop in yield with increasing salinity was observed in 1993 and 1994. Analysis of weather data for 1993–1994 suggests that the decline in yield was due to interactions between saline irrigation and prolonged heat wave events occurring during crop development. Further experimental work (1997) revealed that tuber yield was most sensitive to combined salt and heat stress when heat waves occurred at 40–60 days after emergence. The combined stress apparently leads to the collapse of mechanisms for avoiding salt accumulation in young expanding leaves, resulting in failure of vegetative growth recovery and a consequent reduction in the leaf area index and canopy functioning. The relationship between tuber sink demand and available photoassimilate supply at certain stages of plant development is discussed with reference to the ability of the potato plant to recover from the combined stress.  相似文献   

10.
Subsoil constraints are major limiting factors in crop production in many soils of southern Australia. A field study examined effects of deep incorporation of organic and inorganic amendments in 30–40 cm on soil properties, plant growth and grain yield of wheat (Triticum aestivum var. Ambrook) on a Sodosol with dense sodic subsoil with or without lucerne history in a high rainfall region (long-term average annual rainfall 576 mm) of Victoria. Amendments were applied at a rate of 10–20 t ha−1. Deep ripping alone and deep ripping with gypsum did not significantly affect grain yields. In comparison, application of organic materials doubled biomass production and increased grain yield by 1.7 times. Organic amendment-treated plots produced 60% more grains per area than the untreated control. The crop extracted over 50 mm extra water from below 40 cm soil in organic amendment-treated plots than the untreated control. Nitrogen uptake was almost doubled (403 kg ha−1) in the organic amendment-treated plots than the untreated control (165 kg ha−1). The improved yield with amendments was related to an increase in plant available water in the hostile subsoil, and prolonged greenness of leaves and supply of nitrogen and other nutrients.  相似文献   

11.
Experiments at Bharatpur, Pantnagar, Berhampur, Mohanpur, New Delhi, S.K. Nagar, Kangra and Sriganganagar, India were sown with oilseed Brassica cultivars Varuna and an important cultivar for the area on 10 dates at weekly intervals. Data of experiments conducted previously at Hisar and Ludhiana as available in reports were also used for the study. Mustard aphid (Lipaphis erysimi) appearance on inflorescences of the plants was positively correlated to a maximum temperature between 20–29 °C in the preceding week and also to a morning relative humidity (RH) >92% and daily mean RH of >75%. Long hours of leaf wetness and minimum temperature >5 °C also favoured aphid infestation. Regional and cultivar specific models were developed to predict the crop age at which the mustard aphid first appears on the crop, the peak number of aphids and the crop age at peak number at least 1 week ahead of first appearance of the pest on the crop. These will allow growers to apply insecticides in a more timely and effective manner. Here we report only the models that were found effective based on validation in the 2 years.  相似文献   

12.
Field trials were conducted at Samaru in the northern Guinea and at Bakuta and Kadawa in the Sudan Savanna ecological zones of Nigeria to identify suitable herbicides for weed control in irrigated onion. The herbicides tested were chlorthal-dimethyl, fluorodifen and oxadiazon. In the trials each herbicide treatment was compared with an identical treatment which received supplementary hand-weeding. The results of these experiments show that oxadiazon at 1·0–2·0 kg a.i./ha, with or without supplementary hoe-weeding at 6 weeks after transplanting, combined effective weed control with high bulb yields in irrigated dry season onions. While fluorodifen at 1·5 kg a.i./ha followed by supplementary hoe-weeding may be effective at sites with low weed infestation, a higher rate (3·0 kg/ha) may be desirable at sites with a higher broad-leaved weed infestation. Chlorthaldimethyl at 10·0 kg a.i./ha effectively controlled weeds at all the sites and gave high onion yields at sites with 6–12% clay; the selectivity was, however, lower at Bakura with very light soil. Uncontrolled weed growth caused 49–86% reduction in the bulb yields compared with the best herbicide treatments.  相似文献   

13.
Grape cane waste was investigated as a potential source of high-value phytochemicals with medicinal and anti-phytopathogenic applications. Extraction yields of trans-resveratrol and trans--viniferin from Vitis vinifera cv. Pinot Noir grape cane were 3.45 ± 0.04 and 1.30 ± 0.07 mg g−1 dw, respectively. The analyte extraction efficiencies were investigated using protic and aprotic solvents. Yields varied 22-fold over the range of solvent systems investigated, demonstrating the importance in solvent polarity and hydrogen bonding capability for efficient extractions. The current study suggests that these compounds can be quantitatively extracted from grape cane residue using low-cost, environmentally benign, and non-toxic aqueous alcoholic solvent systems such as ethanol:water mixtures. With current commercial values of trans-resveratrol and trans--viniferin between US$ 2000 and US$ 3000 per kg, established stilbene yields from cane waste could represent an agricultural coproduct valued at US$ 2000–US$ 3000 per hectare of production. At present levels of worldwide wine grape production, the extraction of trans-resveratrol and trans--viniferin from grape cane waste may reach a global economic value of >$30 billion.  相似文献   

14.
Avoidable losses and economic injury levels (EILs) were computed for the sorghum head bug, Calocoris angustatus Leth., on three cultivars during three rainy seasons (1985–1987) at ICRISAT. Grain yield in plots protected with 2–5 insecticide sprays (carbaryl at 500 g a.i./ha) between the half-anthesis and the dough stage was significantly higher than in untreated plots, with cost-benefit ratios > 1. Plots that were not protected at half-anthesis and/or complete-anthesis, and at milk and dough stages, suffered a significant loss in yield. Bug damage spoiled the grain quality in terms of germination, 1000-grain mass, grain hardness and percentage floaters. Three to four sprays between complete-anthesis and the dough stage prevented a significant reduction in grain quality. Head bug density at half-anthesis, complete-anthesis, milk and dough stages was significantly and negatively associated with grain yield. Bug density at different stages explained 43–94% of the variance in yield. Direct effects of bug numbers at the milk stage and the indirect effects of head bug density at other stages through the milk stage contributed towards maximum reduction in yield. Maximum avoidable losses were recorded in cultivar ICSV 1 (88·6%), followed by CSH 1 (69·9%), and CSH 5 (53·9% in 1986 and 55·0% in 1987). Loss in grain yield/ha due to one insect/panicle at half-anthesis and that based on natural increase, were 548 and 232 kg in CSH 5 during 1986 and 1987, respectively, 251 kg in ICSV 1, and 77 kg in CSH 1. EILs based on a cost-benefit ratio of 1:1 ranged from 1·3–1·4 insects/panicle for CSH 1, 0·4 for ICSV 1, and 0·4–0·6 and 0·2–0·4 for CSH 5 during 1986 and 1987, respectively. Simple cost estimates for insecticide sprays and the resultant saving in grain yield are a useful tool for decision-making in pest management.  相似文献   

15.
Wheat gluten films were cast from aqueous dispersions containing 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) as cross-linking reagents and glycerol as a plasticizer. Cross-linking was carried out to improve film properties such as water sensitivity and tensile strength. Films were characterized by measuring protein and water content, amount of amino groups, swelling of the films in water, and mechanical properties such as tensile strength (σmax) and strain at maximum stress ( at σmax). The use of different ratios of EDC to COOH resulted in different tensile properties and different percentage of swelling, which was attributed to the degree of cross-linking in the film. At a ratio of EDC/NHS/COOH=0.5/0.5/1, films had a water content of 10–11.5% and showed the highest σmax (2.8±0.9 MPa), the lowest at σmax (142±67%), and the lowest swelling (46%) compared to σmax=1.7±0.4 MPa, at σmax=257±63%, and swelling=68% for native gluten films.  相似文献   

16.
Multiple novel vegetable oil-based polyols were synthesized from the reaction-addition to epoxidized soybean oil (ESBO) by a series of acid acyl moieties derived from vegetable oils. The acid acyl moieties were linoleic acid (LA), ricinoleic acid (RC), ricinoleic acid estolide (RC estolide) and hydrolyzed bodied soybean oil (HBSBO). LA and RC were commercially available but RC estolide and HBSBO were synthesized by enzymatic catalytic reactions. In the reaction-addition, ESBO was heated with the acid acyl moieties at 170 °C, atmospheric pressure without any catalyst and solvent. The synthesized vegetable oil-based polyols had acid numbers less than 10 (mg KOH/g), hydroxy numbers of 82–152 (mg KOH/g), and hydroxyl equivalent weights of 370–680. The polyols made from RC estolide and HBSBO had improved numbers of OH equivalent weight comparing to the numbers from alkoxyl hydroxyl soybean oil which is widely used commercial soy-based polyols.  相似文献   

17.
The production of oleoresin from Pinus trees is a relevant economic activity in developing countries, since it provides terpenes used in the chemical industry. The oleoresin production by trees of Pinus elliottii in southern Brazil was investigated. Trees of approximately 28 years of age were individually analyzed for oleoresin yield using the bark streak method of wounding for resin tapping. Plain wounding and wounding followed by application of commercial resin stimulant paste, composed of an ethylene precursor (CEPA) and sulphuric acid, were used as reference treatments. The optimum concentrations of CEPA and sulphuric acid in the stimulant paste were investigated in relation to oleoresin yield, as well as the shape of wound and tree diameter. The replacement of CEPA with auxin in the resin stimulant paste was also evaluated. The results showed that both horizontal and V-shaped streaks are equivalent for oleoresin yield. Trees with larger diameter at breast height, defined as the trunk diameter 1.4 m above the ground (22–23.5 cm) yielded more oleoresin than their smaller counterparts (18–19.5 cm). Oleoresin yield was equivalent with stimulant pastes containing between 1.5 and 4.5% CEPA. Trees exposed to stimulant pastes containing from 3 to 4.5% CEPA had average year oleoresin yield above 5 kg. The use of 20% sulphuric acid in the stimulant paste resulted in higher oleoresin yields. Auxin (2,4-D at 1 mM) was effective in replacing CEPA in the stimulant paste, particularly in smaller DBH trees or after 1 year of application in larger DBH individuals. In conclusion, cost reductions on resin tapping can be achieved by adjusting stimulant paste components and managing subsets of trees in specific fashion based on DBH ranges.  相似文献   

18.
Performance of improved guayule lines in Australia   总被引：1，自引：0，他引：1  
Guayule (Parthenium argentatum Gray) is a potential source of commercial natural rubber. Its commercialisation depends mainly on economical plant production. The objective of this study was to evaluate the performance of improved lines in Australia. Seeds from five improved lines (AZ-1, AZ-2, AZ-3, AZ-5 and AZ-6) and two previously developed guayule lines (N 565 and 11591) were obtained from the Agricultural Research Service (ARS) of the United States Department of Agriculture (USDA). Seedlings from these lines were grown in a glasshouse for 3 months and later transplanted in a field experiment in early September 2001. Plant height and width were monitored from transplanting to 62 weeks at regular intervals. After 62 weeks, plant dry matter production, rubber and resin content, and yields were analysed. Plant height and width of the improved lines were higher than N 565 and 11591. Plant dry matter, rubber and resin yields were significantly different among lines. Of the five lines, AZ-1 and AZ-2 produced rubber yields of 620 and 550 kg/ha, respectively and these yields were significantly greater than for N 565 (371 kg/ha) and 11591 (391 kg/ha). AZ-1 and AZ-2 also produced significantly higher resin yields, 727 and 668 kg/ha, respectively, than those for N 565 (436 kg/ha) and 11591 (325 kg/ha). Rubber and resin yield increase of lines, AZ-1 and AZ-2, were in the range of 41–68% and 53–123%, respectively over N 565 and 11591. AZ-1 tended to produce higher rubber and resin yields than AZ-2 but exhibited highly variable plant height (CV=25%) and width (CV=41%) indicating potential for further genetic improvement. AZ-2 offers the best combination of desirable characters including early vigour, uniformity and comparatively higher rubber and resin yields.  相似文献   

19.
In a search for alternatives to methyl bromide for controlling carnation vascular wilt caused by Fusarium oxysporum f. sp. dianthi (Fod), poultry manure plus soil solarization was studied in soil under greenhouse conditions in four 2-year experiments. These were conducted in naturally infested soil to compare the effects of this treatment with soil solarization alone and methyl bromide. Soil treatments were performed during June 2000 for Experiment 1, from July to mid-August 2002 for Experiment 2, from late July to late August 2006 for Experiment 3 and from late May to late June 2008 for Experiment 4. Additionally, a treatment with commercial poultry manure pellet plus soil solarization was included in the two latter experiments. Poultry manure caused reductions of Fod viability in soil samples at depths of 15 and 30 cm, ranging respectively from 93 to 100% and 89 to 100% for Experiments 1, 2 and 3. Carnations planted in plots treated either with poultry manure, methyl bromide or soil solarization had lower final disease incidences, smaller areas under their disease progress curves and higher yields in comparison with untreated plots in Experiments 2, 3 and 4. In Experiment 1, soil solarization was performed under suboptimal conditions, and it provided disease levels and yields similar to those of the untreated control plots. Nevertheless, under the same conditions, previous amendment of Fod-infested soil with poultry manure increased disease control over soil solarization alone, improved carnation yield and quality and also increased plant vigor, thus providing a satisfactory alternative to methyl bromide. The application of organic amendment to the same plot before every crop cycle is recommended to ensure continuous disease control, but the rates of application could be reduced to half for the third and fourth crop cycles, thereby reducing undesirable environmental effects.  相似文献   

20.
Permanent raised beds are being proposed for the rice–wheat system in the Indo-Gangetic Plain to increase its productivity and to save water. It is not clear whether reported water savings in rice arise from the geometry of the beds per se or from the particular water management that keeps the soil in aerobic conditions and that can also be applied on flat land. Moreover, little research has been reported on direct seeding of rice on raised beds and on the effect of raised beds on the subsequent wheat crop. In this paper we compare the yield, input water (rainfall and irrigation) use and water productivity of dry-seeded rice on raised beds and flat land with that of flooded transplanted and wet-seeded rice, and analyze the effects of beds on the subsequent wheat crop. The experiment was conducted in 2001–2003 at New Delhi, India.

Rice yields on raised beds that were kept around field capacity were 32–42% lower than under flooded transplanted conditions and 21% lower than under flooded wet-seeded conditions. Water inputs were reduced by 32–42% compared with flooded rice, but could also be accomplished with dry seeding on flat land with the same water management. Reduced water inputs and yield reductions balanced each other so that water productivity was comparable among most treatments. Wheat yield was 12–17% lower on raised beds than on flat land with conventional (20 cm) row spacing. Neither wheat nor rice on raised beds compensated for the loss in rows by extra tillering or leaf growth at the edges of the rows. There was no carry-over effect of type of land preparation in rice on the growth and yield of the subsequent wheat crop. Further research on raised beds should focus on the selection of suitable rice and wheat varieties, soil health issues such as nematodes and micro-nutrient deficiencies, weed control, bed stability and long-term carry-over effects from one crop to the other.  相似文献   


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