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1.
《Industrial Crops and Products》2005,21(3):293-307
Both crambe (Crambe abyssinicia, Hochst) and rape (Brassica napus L. and Brassica rapus L.) are cool season crops, thus they may have potential as irrigated, winter rotational crops in the low deserts of the southwestern United States and northern Mexico. Currently, no information is available on the effects of fall planting date on the production of these crops. The objectives of this study were (1) to determine the effects of fall planting date on flowering patterns, seed yield, and oil content of crambe and two species of rape, and (2) to determine the suitability of rape and crambe as rotational crops for the low deserts of the southwestern United States. Nine cultivars of rape and one cultivar of crambe were planted at the Maricopa Agricultural Center on three dates in November and December of 1995 and four dates from October through December of 1997 on a variable Mohall sandy loam soil (fine-loamy, mixed hyperthermic, Typic Haplargid). Five of the rape cultivars were B. napus types and the remaining four were B. rapus. One was an industrial rape (R-500) and the other eight were Canola types. Seed yield, oil concentration, and seed weight were determined. In 1996, the percent of plants flowering was observed visually on a periodic basis. In 1998, detailed imaging of flowering was done periodically using a digital camera. Planting date affected water application by controlling the length of the growing season. Our plants were taller, oil content was higher, seed weights were comparable, days to flowering were more than doubled, and seed yields were lower than plants from spring plantings in the Northern Great Plains. In both years of the study, the highest yields were obtained when rape and crambe were planted in November, which would fit well with cotton harvest dates. Lodging was a serious problem in rape. Crambe was sensitive to frost and could fail in some years. Only R-500 matured early enough to be used in rotation with current cotton cultivars. In addition to the onset of flowering, the automated method for estimating flowering was able to detect differences between Brassica species and cultivars and to measure the duration of flowering. Each species had a distinctive flowering pattern. Planting dates also affected the pattern and efficiency of flowering. Reproductive efficiency appeared to change with planting date and in general, October and November planting dates produced seed with higher oil content and seed weights than December planting dates. 相似文献
2.
Weeds are a major constraint for organic crop production. Previous research has found that cover crops in reduced tillage systems can provide weed interference, subsequently reducing inputs and improving crop yield. However, questions remain about effects of cover crop species identity and cover crop biomass on weed suppression and crop yield. This four-year study investigated how winter cover crops grown alone or in mixture influenced weed presence and crop yield in a reduced tillage organic vegetable system. Treatments were barley (Hordeum vulgare L.), crimson clover (Trifolium incarnatum L.), mixed barley + crimson clover, and a no-cover crop control. Plots were flail-mowed and strip-tilled prior to planting main crops (2011 and 2012: broccoli Brassica oleracea L.; 2013 and 2014: crookneck squash Cucurbita pepo L.). We measured density, diversity, and community composition of weeds and viable weed seeds, changes in weed percent cover within growing seasons, and crop yield. We found that the presence of barley, crimson clover, or barley + crimson clover reduced weed density by 50% relative to the control. Cover crop biomass negatively influenced weed density and weed seed diversity, and positively influenced squash yield. Weed percent cover within growing seasons did not respond differentially to cover crop treatment. Cover crop treatment and cover crop biomass had no influence on weed or weed seed community composition. These results suggest that reduced tillage winter cover crops in mixture or monoculture can similarly suppress weeds and improve yield, primarily due to biomass effects. 相似文献
3.
Camelina (Camelina sativa), guayule (Parthenium argentatum), lesquerella (Physaria fendleri), and vernonia (Centrapalus pauciflorus [formerly Vernonia galamensis]) are either under limited commercial production or being developed for production in the southwestern USA. Insect pests are a potential economic threat to all these new crops, with Lygus hesperus, the western tarnished plant bug, among the most prominent due to its regional abundance and propensity to feed on reproductive plant tissue. The objectives of this study were to establish baseline data on the feeding behavior and potential impact of L. hesperus on camelina, guayule, lesquerella and vernonia. Behavioral observations of adult females and males, and nymphs of this insect were made in the laboratory. Insects spent ≈35% of their time either probing (=tasting) or feeding on various reproductive and vegetative tissues of guayule, lesquerella or vernonia, but only 20% on camelina. When insects did probe and feed they preferred reproductive tissues, primarily flowers and siliques/achenes, and there were differences in these behaviors relative to crop but not generally to insect stage or sex. Insects probed and fed more on flower tissue of guayule and vernonia compared with camelina and lesquerella, and more on siliques of lesquerella compared with achenes of vernonia. When probing and feeding on vegetative tissue, there was generally a preference for stems compared with leaves in all crops except guayule. Results show that L. hesperus will readily feed on the economically important tissues of all crops, and although research has shown that this feeding did not consistently affect lesquerella yield, further work will be needed to determine if such feeding poses a risk to commercial production of camelina, guayule or vernonia. 相似文献
4.
R. A. BYERS C. C. BAHLER‡§ W. L. STOUT K. T. LEATH L. D. HOFFMANN † 《Grass and Forage Science》1994,49(3):316-323
Extensive slug damage reported for lucerne ( Medicago sativa L.) establishment in grass sod and small grain fields when using conservation tillage prompted this 3-year study on establishing lucerne in maize ( Zea mays L.). Different crop residues were created by harvesting maize for grain and silage and including a silage+rye ( Secale cereale L.) winter cover crop treatment. Conventional tillage (ploughed in spring) following grain harvest was included as a control. In addition, a combination treatment of methiocarb bait broadcast on the surface and carbofuran granules applied in the furrow with the seed was compared with an untreated control. Finally, three planting dates, early and late April and late May, simulated the spring planting season. Planting lucerne in the different maize residues had a significant effect on lucerne yields, especially the silage+rye residue treatment, which caused the lowest lucerne yields. Highest yields of lucerne occurred when it was planted after silage, a treatment in which residue was minimal.
The earliest planting date gave the highest lucerne yields in the establishment year. Slugs did not reduce the establishment of lucerne in any maize residue, nor were lucerne yields affected by slug feeding. This was attributed to the low slug populations observed early in the growing season. Establishing and producing lucerne in maize residues was more successful in this study because of the lower slug populations than those usually encountered in grass sod or small grain residues. 相似文献
The earliest planting date gave the highest lucerne yields in the establishment year. Slugs did not reduce the establishment of lucerne in any maize residue, nor were lucerne yields affected by slug feeding. This was attributed to the low slug populations observed early in the growing season. Establishing and producing lucerne in maize residues was more successful in this study because of the lower slug populations than those usually encountered in grass sod or small grain residues. 相似文献
5.
Foliar pathogens such as Zymoseptoria tritici and Puccinia striiformis causing septoria leaf blotch and yellow rust respectively can cause serious yield reduction in winter wheat production, and control of the diseases often requires several fungicide applications during the growing season. Control is typically carried out using a constant fungicide dose in the entire field although there may be large differences in crop development and biomass across the field. The objective of the study reported in this paper was to test whether the fungicide dose response curve controlling septoria leaf blotch and other foliar diseases in winter wheat was dependent on crop development and biomass level. If such a biomass dependent dose response was found it was further the purpose to evaluate the potential to optimize fungicide inputs in winter wheat crops applying a site-specific crop density dependent fungicide dose. The study was carried out investigating fungicide dose response controlling foliar diseases in winter wheat at three biomass densities obtained growing the crop at three nitrogen levels and using variable seed rates. Further the field experiments included three fungicide dose rates at each biomass level, an untreated control, and 75%, 50% and 33% of the recommended fungicide dose rate and the experiments were replicated for three years. Crop biomass had a significant influence on occurrence of septoria and yellow rust with greater disease severity at increasing crop biomass. In two of three years, the interaction of crop biomass and fungicide dose rate had a significant influence on disease severity indicating a biomass-dependent dose response. The interaction occurred in the two years with high yield potential in combination with severe disease attack. If the variation in crop density and biomass level obtained in the study is representative of the variation found cultivating winter wheat in heterogeneous fields, then there seems to be scope for optimizing fungicide input against foliar diseases site-specific adapting the dose according to crop density/biomass. 相似文献
6.
《Field Crops Research》1999,61(2):97-107
Crotalaria (C. ochroleuca G. Don.) used as a green manure may improve the productivity of maize–bean cropping systems in eastern Africa. To test this hypothesis, three field studies were conducted over three consecutive cropping seasons at Kawanda Agricultural Research Institute in Uganda. In the first season, crotalaria biomass was produced in pure stands or in intercrop systems with either common beans (Phaseolus vulgaris L.) or maize (Zea mays L.) as companion crops. Crotalaria was sown at planting and three weeks after planting the food crops. The biomass of early planted crotalaria was mulched, that of late planted crotalaria was incorporated into the soil at planting of the following crop. The first subsequent crop was maize, and the second was either beans (in two seasons) or maize (in one season). In the crotalaria production season, mean yield losses of maize through intercropping with early or late sown crotalaria were 40 and 22%, respectively; the corresponding values for beans were 45 and 14%. In the first cropping season after crotalaria production, the increase in maize grain yield on account of crotalaria averaged 39%; the best response (68% increase) to crotalaria was obtained with early sown sole crotalaria applied as mulch. Major differences in soil mineral nitrogen content among the treatments occurred at the six-leaf stage of maize only. In the second cropping season following crotalaria production, the mean increases in seed yields of beans or maize, due to crotalaria, were 23 and 19%, respectively, indicating a considerable residual effect of crotalaria green manure. The decrease in bulk density, and the increase in water infiltration capacity of the soil suggest that the yield stimulation because of crotalaria not only resulted from the increased nitrogen supply, but also from more favorable soil physical properties. Considering the competitive effect of crotalaria with the food crops and the positive effect on yields of subsequent crops, two options are especially promising: incorporation of crotalaria produced by relay intercropping with beans and mulching of early sown crotalaria produced in pure stands. 相似文献
7.
Crop management plays an important role in the transition from a deepwater rice to a flooded rice production system but information about optimum management strategies are currently lacking. The goal of this study was to determine the effect of planting date and variety on flooded rice production in the deepwater area of Thailand. Two experiments were conducted at the Bang Taen His Majesty Private Development Project in 2009 and 2010 to represent conditions prior to flooding (early rainy season) and after flooding (dry season). The early rainy season crop covered the period from May to October 2009, while the dry season crop covered the period from November 2009 to April 2010. The experimental design was a split plot with four main plots and three sub plots replicated four times. The treatments for the main plot were various planting dates, while the treatments for the sub plots were rice varieties. The dates of the critical developmental phases of rice were recorded and biomass was sampled during the growing period. The collected data were statistically analyzed using ANOVA and treatment means were compared to identify the appropriate plating date and the best variety for the area. The highest average yield was obtained for variety PSL2 across transplanting dates from June 19 to July 23, with an average yield of 3898 kg ha−1. The dry season crop showed that both biomass and yield were affected by the interaction between planting date and variety. The highest yield was obtained for variety PTT1 transplanted on November 9. The research showed that the variety PSL2 is the most suitable variety for early rainy season production with a transplanting date ranging from June 19 to July 23, while the variety PTT1 planted on November 9 was the best management practice for the dry season crop. However, a high yielding flooded rice variety that has a short growth duration is still needed for this area. 相似文献
8.
Echinochloa crus-galli, a C4 grass, is one of the world’s most serious weeds. Weed management decisions for this species can be derived from knowledge of its seed biology. Studies were conducted to determine the effects of light on germination; seed burial depth and rice residue on emergence and growth; and flooding time and depth on emergence, survival and growth of this species. Light stimulated seed germination but it was not an absolute requirement for germination. The proportion of seeds germinating was greatest for seeds placed on the soil surface (92%), and emergence declined with increasing burial depth in soil; no seedlings emerged from the depth of 8 cm. A burial depth of only 0.4 cm reduced seedling emergence by 50%. Seedling emergence and seedling biomass were reduced by the addition of high level (6 ton ha−1) of rice residue to the soil surface. Early and deep flooding significantly suppressed growth of E. crus-galli seedlings. In flooded conditions, with increased water depth the weed allocated more biomass to shoots at the expense of roots. The information gained from this study could contribute to improve weed control approaches. Soil inversion by tillage to bury weed seeds below their maximum depth of emergence, use of crop residue as mulch and early flooding of the crop could serve as important tools for managing E. crus-galli and other weed species with similar germination requirements. These management options, however, would need to be compatible with other crop management requirements. 相似文献
9.
W. B. Collins 《American Journal of Potato Research》1977,54(7):339-352
The basis of difference in field growth and yield in Netted Gem potato plants grown from greenhouse transplants, from seed which was greensprouted for two weeks prior to planting and from seed which was retained in storage until planting was studied by measuring changes in plant dry weight and leaf area throughout the season. Cut seed, approximately 70g in size, which were either two or four-cut from 142g or 283g mother tubers respectively, were used in the comparisons. Transplants were started in 7.6 cm peat pots in the greenhouse and were transplanted to the field when 10 cm high. The greensprouted seed was cut from mother tubers which had been sprouted under fluorescent light at 15–18°C for two weeks producing strong sprouts 5 mm long. Transplants, greensprouted seed and seed from mother tubers held in 3°C storage were all planted in the field May 30, 1974, coinciding with commercial plantings of Netted Gem in the province. Backup field experiments, comparing similarly treated greensprouted and storage seed and transplants, were conducted in 1974 and 1975 but were not subjected to growth analysis. All plantings were grown on a Riverbank sandy loam soil. The 1974 growing season in New Brunswick was excellent while that for 1975 was dry and required extensive irrigation. The use of transplants established a substantial advantage in terms of early emergence and yields were consistently and significantly greater than those of greensprouted-seed and unsprouted-seed plants. The transplant yield advantage was attributed to the fact that tuberization was advanced substantially compared with the latter two types. Higher relative growth rates were associated with later emergence so that the rate for plants growing from unsprouted seed was greater than that for plants growing from greensprouted plants which, in turn, was superior to that of transplants. This pattern was maintained through the season. Consequently, small advantages in time of emergence, such as that obtained with greensprouted-seed plants, were not accompanied by significant yield differences. Canopy size decreased as emergence was delayed and canopy size differences were determined largely by the amount of branching. As canopy size decreased and emergence was delayed, the net assimilation rate was found to increase. 相似文献
10.
Evaluating decision rules for dryland rotation crop selection 总被引：1，自引：0，他引：1
No-till dryland winter wheat (Triticum aestivum L.)-fallow systems in the central Great Plains have more water available for crop production than the traditional conventionally tilled winter wheat-fallow systems because of greater precipitation storage efficiency. That additional water is used most efficiently when a crop is present to transpire the water, and crop yields respond positively to increases in available soil water. The objective of this study was to evaluate yield, water use efficiency (WUE), precipitation use efficiency (PUE), and net returns of cropping systems where crop choice was based on established crop responses to water use while incorporating a grass/broadleaf rotation. Available soil water at planting was measured at several decision points each year and combined with three levels of expected growing season precipitation (70, 100, 130% of average) to provide input data for water use/yield production functions for seven grain crops and three forage crops. The predicted yields from those production functions were compared against established yield thresholds for each crop, and crops were retained for further consideration if the threshold yield was exceeded. Crop choice was then narrowed by following a rule which rotated summer crops (crops planted in the spring with most of their growth occurring during summer months) with winter crops (crops planted in the fall with most of their growth occurring during the next spring) and also rotating grasses with broadleaf crops. Yields, WUE, PUE, value-basis precipitation use efficiency ($PUE), gross receipts, and net returns from the four opportunity cropping (OC) selection schemes were compared with the same quantities from four set rotations [wheat-fallow (conventional till), (WF (CT)); wheat-fallow (no-till), (WF (NT)); wheat–corn (Zea mays L.)-fallow (no-till), (WCF); wheat–millet (Panicum miliaceum L.) (no-till), (WM)]. Water use efficiency was greater for three of the OC selection schemes than for any of the four set rotations. Precipitation was used more efficiently using two of the OC selection schemes than using any of the four set rotations. Of the four OC cropping decision methods, net returns were greatest for the method that assumed average growing season precipitation and allowed selection from all possible crop choices. The net returns from this system were not different from net returns from WF (CT) and WF (NT). Cropping frequency can be effectively increased in dryland cropping systems by use of crop selection rules based on water use/yield production functions, measured available soil water, and expected precipitation. 相似文献
11.
Cover crops and mulches are a suitable choice for sustainable agriculture because they improve weed control and crop performance. The aim of this research was to investigate weed control and nitrogen supply by using different winter cover crop species which were converted into mulches in spring. We carried out a 2-year field experiment where a tomato crop was transplanted into four different types of mulches coming from winter cover crops [hairy vetch (Vicia villosa Roth.), subclover (Trifolium subterraneum L.), oat (Avena sativa L.), and a mixture of hairy vetch/oat)] and in conventional treatment (tilled soil without mulch). The mixture of hairy vetch/oat cover crop produced the highest aboveground biomass (7.9 t ha−1 of DM), while the hairy vetch accumulated the highest N in the aboveground biomass (258 kg N ha−1). The oat cover crop was the most effective cover crop for suppressing weeds (on average −93% of weed aboveground biomass compared to other cover crops). After mowing the cover crop aboveground biomass was placed in strips as dead mulch into which the tomato was transplanted in paired rows. Weed density and total weed aboveground biomass were assessed at 15 and 30 days after tomato transplanting to evaluate the effect of mulches on weed control. All mulches suppressed weeds in density and aboveground biomass compared to the conventional system (on average −80% and −35%, respectively). The oat was the best mulch for weed control but also had a negative effect on the marketable tomato yield (−15% compared to the conventional treatment). Amaranthus retroflexus L. and Chenopodium album L. were typical weeds associated with the conventional treatment while a more heterogeneous weed composition was found in mulched tomato. Legume mulches, in particular hairy vetch, gave the best marketable tomato yield 28% higher than the conventional system both with and without nitrogen fertilization. This research shows that winter cover crops converted into dead mulch in spring could be used successfully in integrated weed management programs to reduce weed infestation in tomato crops. 相似文献
12.
Evaluation of early mature naked oat varieties as a summer-seeded crop in dryland northern climate regions 总被引：1，自引：0，他引：1
Increased land degradation and shortage of forage resources for animal production over-winter have accentuated the need for alternative cropping systems in northeast China. While short frost-free period and cool temperatures are major limitations to cereal grain production in the northern regions of China (45°N, 122°E), crop varieties that are able to produce food and feed in short growing season and tolerant to low temperature may extend the total cropping period. Three hulless oat (Avena sativa L.) lines, Baiyan 9015, Baiyan 9017 and Baiyan 9044, were bred and tested for 3 years (2004–2006) to determine their suitability for summer seeding in a double cropping system. The new lines were sown both in the spring and summer to provide growers with opportunities to harvest two grain-crops in a year. Averaged across 3 years, Baiyan 9044 produced 2.5 and 1.6 Mg ha−1 yr−1 grain yield when sown in spring and summer, respectively. The new lines seeded in 20th or 21st July and harvested in early October allowed utilization of an average of over 1500 growing degree days (GDDs). For grain yield alone, the net income for two oat crops a year was up to 1390 Chinese yuan (RMB) ha−1, more than that of growing a single oat crop in 3 years, or in most cases, equivalent to monocultured corn (Zea mays L.) production, the dominant crop in the region. In addition, an average of 5 Mg ha−1 of oat straw was produced as valuable forage fodder for the livestock industry, which was in great demand for over-wintering animals. Furthermore, in the traditional single small grain cereal cropping system, bare ground after harvest leads to severe water and wind erosions. Our results indicate that the new oat lines could be a potential crop for summer seeding, particularly when spring-seeded crops fail due to abiotic (hail, drought, etc.) or biotic (e.g. insects) stresses. The double cropping system provides growers with a potential opportunity to facilitate the farming strategy of food, cash crops and control soil erosion in the region. 相似文献
13.
J. Marinus 《Potato Research》1992,35(4):343-354
Summary Young seed tubers of several cultivars were exposed to storage temperatures of 4–24°C in light and dark intended to optimise
their growth vigour following early plantings. In five experiments during four autumn and winter periods, the effects of storage
conditions on subsequent initial plant development in the glasshouse were studied. Storage of seed potatoes for 2 months at
temperatures of 12°C or higher greatly increased early plant development of five cultivars following early plantings. Light
during storage had a favourable effect, but desprouting before planting was greatly disadvantageous. 相似文献
14.
Under semiarid Mediterranean conditions irrigated maize has been associated to diffuse nitrate pollution of surface and groundwater. Cover crops grown during winter combined with reduced N fertilization to maize could reduce N leaching risks while maintaining maize productivity. A field experiment was conducted testing two different cover crop planting methods (direct seeding versus seeding after conventional tillage operations) and four different cover crops species (barley, oilseed rape, winter rape, and common vetch), and a control (bare soil). The experiment started in November 2006 after a maize crop fertilized with 300 kg N ha−1 and included two complete cover crop-maize rotations. Maize was fertilized with 300 kg N ha−1 at the control treatment, and this amount was reduced to 250 kg N ha−1 in maize after a cover crop. Direct seeding of the cover crops allowed earlier planting dates than seeding after conventional tillage, producing greater cover crop biomass and N uptake of all species in the first year. In the following year, direct seeding did not increase cover crop biomass due to a poorer plant establishment. Barley produced more biomass than the other species but its N concentration was much lower than in the other cover crops, resulting in higher C:N ratio (>26). Cover crops reduced the N leaching risks as soil N content in spring and at maize harvest was reduced compared to the control treatment. Maize yield was reduced by 4 Mg ha−1 after barley in 2007 and by 1 Mg ha−1 after barley and oilseed rape in 2008. The maize yield reduction was due to an N deficiency caused by insufficient N mineralization from the cover crops due to a high C:N ratio (barley) or low biomass N content (oilseed rape) and/or lack of synchronization with maize N uptake. Indirect chlorophyll measurements in maize leaves were useful to detect N deficiency in maize after cover crops. The use of vetch, winter rape and oilseed rape cover crops combined with a reduced N fertilization to maize was efficient for reducing N leaching risks while maintaining maize productivity. However, the reduction of maize yield after barley makes difficult its use as cover crop. 相似文献
15.
In order to determine the critical period of weed control in winter canola (Brassica napus L. cv. Okapi) an experiment was carried out at research field of Tarbiat Modarres University, Tehran, Iran on 2004-2005 growing season. Fourteen experimental treatments which divided into two sets were arranged in Randomized complete blocks design with four replications. In the first set, the crop was kept weed-free from emergence time to two-leaf stage (V2), four-leaf stage (V4), six-leaf stage (V6), eight-leaf stage (V8), early flowering (IF), 50% of silique set (50% SS) and final harvest (H). In the second set, weeds where permitted to grow with the crop until above mentioned stages. In this study critical period of weed control was determined according to evaluate seed bank emerged weed biomass effect on canola grain yield loss using Gompertz and logistic equations. Result showed a critical time of weed control about 25 days after emergence (between four to six-leaf stages) with 5% accepted yield loss. Therefore, weed control in this time could provide the best result and avoid yield loss and damage to agroecosystem. 相似文献
16.
S. Marco 《Potato Research》1981,24(2):135-145
Summary Seed potatoes grown during winter in the Sinai Desert (Sharm el Sheik) yielded in autumn significantly more (17%) than commercial
seed grown in spring. Seeds grown in winter in an agricultural area at Yotvata yielded similarly to the commercial controls.
Almost no spread of PVY or PLRV was found at Sharm probably because of the very low alate population there, whereas at Yotvata
the incidence of PLRV was over 40% probably as a consequence of a high aphid populations during the growing season. Alate
populations were also observed in the Sinai Desert at A-tur, a completely arid area, and at Firan, an isolated oasis where
agriculture is practised. At A-tur only a few alatae were trapped, but large numbers were found at Firan, especially starting
in March, but not during winter the proposed season for growing seed potatoes.
The possibility of growing high quality seed potatoes at Sharm is discussed.
Contribution No 107, 1980 series, Volcani Center. 相似文献
17.
This study aims to assess the risks and opportunities posed by climate change to potato growers in South Africa and to evaluate adaptation measures in the form of changes in planting time growers could adopt to optimise land and water use efficiencies in potato, using a climate model of past, present-day and future climate over southern Africa and the LINTUL crop growth model. This was done for distinct agro-ecosystems in South Africa: the southern Mediterranean area where potato still is grown year round with a doubling of the number of hot days between 1960 and 2050, the Eastern Free State with summer crops only and Limpopo with currently autumn, winter and spring crops where the number of hot days increases sevenfold and in future the crop will mainly be grown in winter. A benefit here will be a drastic reduction of frost days from 0.9 days per winter to 0. Potato crops in the agro-ecosystems will benefit considerably from increased CO2 levels such as increased tuber yield and reduced water use by the crop, if planting is shifted to appropriate times of the year. When the crop is grown in hot periods, however, these benefits are counteracted by an increased incidence of heat stress and increased evapotranspiration, leading in some instances to considerably lower yields and water use efficiencies. Therefore year-round total production at the Sandveld stabilizes at around 140 Mg?ha?1 (yield reduction in summer and yield increase in winter), increases by about 30% in the Free State and stays at about 95 t?ha?1 at Limpopo where yield increase due to CO2 is annulled by a shorter growing season. When the crop is grown in a cool period, there is an additional benefit of a reduced incidence of cold stress and a more rapid canopy development in the early stages of crop growth. In all three areas, potato growers are likely to respond to climate change by advancing planting. In Limpopo, a major benefit of climate change is a reduction in the risk of frost damage in winter. The relevance of these findings for potato grown in agro-ecosystems elsewhere in the world is discussed. 相似文献
18.
Safflower (Carthamus tinctorius L.) is a deep-rooted crop which can tolerate water stress and can be grown in rotation with other crop species. Nitrogen is one of the most important nutrients for the growth and development of safflower; however, the effect of N level on dry matter, accumulation, partitioning, and retranslocation has not been extensively studied. A 2-year field study was therefore conducted with the objective to determine the effect of N fertilization on crop phenology, dry matter, N accumulation, partitioning and retranslocation of safflower grown under rain-fed conditions. Three rates of N were used (0, 100, and 200 kg N ha−1) and two hybrids (CW9048 and CW9050) of safflower were selected. The experiment was conducted during the 2003–2004 (2004) and 2004–2005 (2005) growing seasons on a calcareous sandy loam (Entisols, Orthents, Typic Xerorthent) at the experimental farm of the Aristotle University of Thessaloniki, in Northern Greece. During 2004 spring was quite mild with significant rainfall whereas during 2005 spring was hotter with lower rainfall. Our study found that N fertilization increased biomass at anthesis by an average of 24% and at maturity by an average of 25% compared with the control. Total above ground biomass increased after anthesis in both years, in both hybrids and for all fertilizer treatments. N fertilization increased the dry matter partitioning in leaves + stems and heads at anthesis and also in leaves + stems, seeds, and head vegetative components at maturity. Dry matter translocation was not affected by N fertilization but lower values were found during the second year. N content was affected by the fertilization treatments and increased in those plants treated with fertilizer compared with the controls. In addition, N fertilization increased N retranslocation from the vegetative parts of the plant to the seed, but it did not affect N gain. During the second year, which was drier, there were significant N losses but also greater N translocation efficiency and higher contribution of pre-anthesis N to seed. Seed yield was correlated with the dry matter and N translocation indices, and was higher for the fertilized plants, compared with the control. The present study indicates that N fertilization promoted the growth of safflower and increased the dry matter yield, N accumulation, translocation and seed yield under rain-fed conditions. 相似文献
19.
Alpha Bocar Baldé Eric ScopelFrançois Affholder Marc Corbeels Fernando Antonio Macena Da SilvaJosé Humberto Valadares Xavier Jacques Wery 《Field Crops Research》2011,124(2):240-251
In the context of conservation agriculture on small scale farms of the Brazilian Cerrado, we hypothesized that planting a cover crop in relay with a commercial crop improves the efficiency of use of available natural resources, increasing biomass for use as fodder without reducing the grain yield of the main crop. The objective of this study was to measure the performance of two intercropped systems in terms of total above-ground biomass production and maize (Zea mays) grain yield: pigeon pea (Cajanus cajan) and Brachiaria (Brachiaria ruziziensis) sown as cover crops in established maize under a no-tillage management. The cover crops were sown at two different dates and a comparison was made with the three crops sown as a sole crop at the early sowing date. The experiment was conducted during the 2007-2008 and 2008-2009 growing seasons. Maize grain yield was not reduced by the presence of the relay cover crops in comparison with maize as the sole crop, even when the cover crop was sown soon after maize emergence. In contrast, the production of above-ground biomass by the cover crop was significantly lower when grown with maize than it was when grown as a sole crop. In the intercropped systems, when sown early, the cover crop produced higher total biomass than when sown late. Total above-ground biomass production of maize intercropped with a cover crop was much higher than that of any of the crops sown alone: the total biomass (average of the two growing seasons) produced by maize and pigeon pea was more than double that of maize grown alone. The land equivalent ratio (LER) of maize grain yield and biomass production was higher than one whatever the intercropped system used. It was particularly high when maize was intercropped with early sown pigeon pea; grain yield LER and biomass LER reaching, respectively, 1.72 and 1.73 in 2007-2008 and 2.02 and 2.03 in 2008-2009. These high LER values provide evidence for the complementary and the high efficiency of use of available resources by the intercropped plants and thus the advantage of such systems to produce both maize grain and cover crop forage under the conditions of our study. 相似文献
20.
Summary Ware potatoes were produced from true potato seed by transplanting seedlings to the field in different growing periods to
evaluate environmental constraints of this production method in the Nile delta. In the autumn season, with high temperatures
and long-day conditions during seedling culture in the nursery and transplant establishment in the field, seedling development
was fast, and transplants resumed growth within 5 days of transplanting in the field. Tuber yields ranged between 120 and
160 dt ha−1. In the spring season, with low temperatures and short-day conditions during the initial growing phase, seedling development
in the nursery was slow and biomass partitioning between above ground organs (stems, leaves) and tubers was shifted towards
the tubers. This partitioning was further enhanced by transplanting the seedlings in the field. Seedlings recovered only slowly
from transplanting or died.
It is concluded that potato production via transplants is poor in the spring season when premature tuberization of seedlings
in the nursery leads to slow field establishment and low tuber yield. 相似文献