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1.
Rainfed crop production in northern China is constrained by low and variable rainfall. This study explored the effects of tillage/crop residue and nutrient management practices on maize (Zea mays L.) yield, water use efficiency (WUE), and N agronomic use efficiency (NAE) at Shouyang Dryland Farming Experimental Station in northern China during 2003–2008. The experiment was set-up using a split-plot design with 3 tillage/crop residue methods as main treatments: conventional, reduced (till with crop residue incorporated in fall but no-till in spring), and no-till (with crop residue mulching in fall). Sub-treatments were 3 NP fertilizer rates: 105–46, 179–78 and 210–92 kg N and P ha−1. Maize grain yields were greatly influenced by the growing season rainfall and soil water contents at sowing. Mean grain yields over the 6-year period in response to tillage/crop residue treatments were 5604, 5347 and 5185 kg ha−1, under reduced, no-till and conventional tillage, respectively. Grain yields under no-till, were generally higher (+19%) in dry years but lower (−7%) in wet years. Mean WUE was 13.7, 13.6 and 12.6 kg ha−1 mm−1 under reduced, no-till, and conventional tillage, respectively. The no-till treatment had 8–12% more water in the soil profiles than the conventional and reduced tillage treatments at sowing and harvest time. Grain yields, WUE and NAE were highest with the lowest NP fertilizer application rates (at 105 kg N and 46 kg P ha−1) under reduced tillage, while yields and WUE tended to be higher with additional NP fertilizer rates under conventional tillage, however, there was no significant yield increase above the optimum fertilizer rate. In conclusion, maize grain yields, WUE and NAE were highest under reduced tillage at modest NP fertilizer application rates of 105 kg N and 46 kg P ha−1. No-till increased soil water storage by 8–12% and improved WUE compared to conventional tillage, thus showing potentials for drought mitigation and economic use of fertilizers in drought-prone rainfed conditions in northern China.  相似文献   

2.
In regions with shallow water tables, ground water may have a positive (water supply) or negative (waterlogging or salinization) impact on crops. Reciprocally, crops can influence ground water, altering water table depth and chemical composition. We quantified these reciprocal influences along natural gradients of groundwater depth in flat sedimentary landscapes of the Inland Pampas occupied by wheat, soybean, and maize during two growing seasons (2006/2007 and 2007/2008). We correlated crop yield and groundwater depth maps at the field level and made direct plant, soil and groundwater observations at the stand level across topographic gradients. Water table level largely accounted for spatial crop yield variation, explaining 20–75% of their variance. An optimum groundwater depth range, where crop yields were highest, was observed for all three crop species analyzed (1.40–2.45 m for maize, 1.20–2.20 m for soybean, and 0.70–1.65 m for wheat). The areas within these optimum bands had yields that were 3.7, 3 and 1.8 times larger than those where the water table was below 4 m for wheat, maize, and soybean, respectively. As groundwater levels become shallower than these depth bands, crop yields declined sharply (∼0.05 kg m−2 on average for every 10 cm increase in water table level), suggesting negative effects of waterlogging, root anoxia and/or salinity. Groundwater levels below these depth bands were associated with gradually declining yields, likely driven by poorer groundwater supply.  相似文献   

3.
Long-term (over 15 years) winter wheat (Triticum aestivum L.)–maize (Zea mays L.) crop rotation experiments were conducted to investigate phosphorus (P) fertilizer utilization efficiency, including the physiological efficiency, recovery efficiency and the mass (the input–output) balance, at five sites across different soil types and climate zones in China. The five treatments used were control, N, NP, NK and NPK, representing various combinations of N, P and K fertilizer applications. Phosphorus fertilization increased average crop yield over 15 years and the increases were greater with wheat (206%) than maize (85%) across all five sites. The wheat yield also significantly increased over time for the NPK treatments at two sites (Xinjiang and Shanxi), but decreased at one site (Hunan). The P content in wheat was less than 3.00 g kg−1 (and 2.10 g kg−1 for maize) for the N and NK treatments with higher values for the Control, NP and NPK treatments. To produce 1 t of grain, crops require 4.2 kg P for wheat and 3.1 kg P for maize. The P physiological use efficiency was 214 kg grain kg−1 P for wheat and 240 kg grain kg−1 P for maize with over 62% of the P from P fertilizer. Applying P fertilizer at 60–80 kg P ha−1 year−1 could maintain 3–4 t ha−1 yields for wheat and 5–6 t ha−1 yields for maize for the five study sites across China. The P recovery efficiency and fertilizer use efficiency averaged 47% and 29%, respectively. For every 100 kg P ha−1 year−1 P surplus (amount of fertilizer applied in excess of crop removal), Olsen-P in soil was increased by 3.4 mg P kg−1. Our study suggests that in order to achieve higher crop yields, the long-term P input–output balance, soil P supplying capacity and yield targets should be considered when making P fertilizer recommendations and developing strategies for intensively managed wheat–maize cropping systems.  相似文献   

4.
Forages could be used to diversify reduced and no-till dryland cropping systems from the traditional wheat (Triticum aestivum L.)-fallow system in the semiarid central Great Plains. Forages present an attractive alternative to grain and seed crops because of greater water use efficiency and less susceptibility to potentially devastating yield reductions due to severe water stress during critical growth stages. However, farmers need a simple tool to evaluate forage productivity under widely varying precipitation conditions. The objectives of this study were to (1) quantify the relationship between crop water use and dry matter (DM) yield for soybean (Glycine max L. Merrill), (2) evaluate changes in forage quality that occur as harvest date is delayed, and (3) determine the range and distribution of expected DM yields in the central Great Plains based on historical precipitation records. Forage soybean was grown under a line-source gradient irrigation system to impose a range of water availability conditions at Akron, CO. Dry matter production was linearly correlated with water use resulting in a production function slope of 21.2 kg ha−1 mm−1. The slope was much lower than previously reported for forage production functions for triticale (X Triticosecale Wittmack) and millet (Setaria italic L. Beauv.), and only slightly lower than slopes previously reported for corn (Zea mays L.) and pea (Pisum sativa L.) forage. Forage quality was relatively stable during the last four weeks of growth, with small declines in crude protein (CP) concentration. Values of CP concentration and relative feed value indicated that forage soybean was of sufficient quality to be used for dairy feed. A standard seed variety of maturity group VII was found to be similar (in both productivity and quality) to a variety designated as a forage type. The probability of obtaining a break-even yield of at least 4256 kg ha−1 was 90% as determined from long-term precipitation records used with the production function. The average estimated DM yield was 5890 kg ha−1 and ranged from 2437 to 9432 kg ha−1. Regional estimates of mean forage soybean DM yield ranged from 4770 kg ha−1 at Fort Morgan, CO to 6911 kg ha−1 at Colby, KS. Forage soybean should be considered a viable alternative crop for dryland cropping systems in the central Great Plains.  相似文献   

5.
Biological nitrogen fixation (BNF) as a result of the legumes–rhizobia symbioses is the main source of nitrogen in organic farming systems. Lucerne (Medicago sativa L.), used as green manure or as forage legume, is important on arable farms under dry site conditions. In a field experiment on organically managed agricultural fields, we examined the impacts of the utilisation system (harvested = forage production versus mulched = green manure) and the crop composition (pure lucerne crops versus lucerne–grass mixtures) on yield, biological nitrogen fixation (BNF), soil inorganic N content, N balance and water consumption of autumn-cultivated lucerne crops. The study was conducted at the University of Natural Resources and Applied Life Sciences, Vienna, in eastern Austria—a region characterized by pannonian site conditions (9.8 °C mean annual temperature, 545 mm average total precipitation) and stockless farming systems. Our results indicate that the utilisation system and the crop composition had no marked influence on above- and below-ground dry matter (DM) and N yield, soil inorganic N contents, BNF, or water use efficiency of lucerne. The level of symbiotically fixed N2 in harvested lucerne was 89–125 kg N ha−1 (27–33% Ndfa = nitrogen derived from atmosphere) in the first year and 161–175 kg N ha−1 (47–49% Ndfa) in the second year of the study. The high soil inorganic N supply in the first year increased the N uptake from soil by lucerne and led to a reduced BNF. Under the dry and unfavourable conditions in both study years, the nitrogen release from the legume mulch was retarded and BNF in mulched lucerne was not reduced. Assuming low gaseous N losses by mulching (15–30 kg N ha−1), the green manure system reached a positive N balance (+137 to +186 kg N ha−1) for the subsequent crops because abundant residues remained on the field.  相似文献   

6.
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   

7.
The N contribution of alfalfa (Medicago sativa L.) to the succeeding corn (Zea mays L.) crop (FYC) is widely recognized. However, there is less information regarding the optimum N fertilization rates (ONR) for a second-year corn (SYC) following alfalfa. Thus, the objective of this study was to evaluate the response of SYC after alfalfa to N fertilization under irrigated semiarid conditions. Three field experiments of SYC following alfalfa were conducted between 2007 and 2009 in Northeast Spain. Treatments included the combination of six N rates applied to FYC (0, 50, 100, 150, 200, and 300 kg N ha−1) with four N rates applied to SYC (0, 100, 200, and 300 kg N ha−1). In one of the three fields, high SYC yields (16.8 Mg ha−1) were obtained in plots that remained unfertilized during two consecutive years after alfalfa. On the other two fields, 81-100% of the maximum corn yields were obtained with application of 200 kg N ha−1 to SYC. Results suggest that the typical N fertilizer rates applied to SYC after alfalfa in irrigated semiarid areas (300 kg N ha−1) could be reduced by at least 100 kg N ha−1, with small or no economic penalties and important reductions in N losses.  相似文献   

8.
Appropriate benchmarks for water productivity (WP), defined here as the amount of grain yield produced per unit of water supply, are needed to help identify and diagnose inefficiencies in crop production and water management in irrigated systems. Such analysis is lacking for maize in the Western U.S. Corn Belt where irrigated production represents 58% of total maize output. The objective of this paper was to quantify WP and identify opportunities to increase it in irrigated maize systems of central Nebraska. In the present study, a benchmark for maize WP was (i) developed from relationships between simulated yield and seasonal water supply (stored soil water and sowing-to-maturity rainfall plus irrigation) documented in a previous study; (ii) validated against actual data from crops grown with good management over a wide range of environments and water supply regimes (n = 123); and (iii) used to evaluate WP of farmer's fields in central Nebraska using a 3-y database (2005–2007) that included field-specific values for yield and applied irrigation (n = 777). The database was also used to quantify applied irrigation, irrigation water-use efficiency (IWUE; amount of yield produced per unit of applied irrigation), and the impact of agronomic practices on both parameters. Opportunities to improve irrigation management were evaluated using a maize simulation model in combination with actual weather records and detailed data on soil properties and crop management collected from a subset of fields (n = 123). The linear function derived from the relationship between simulated grain yield and seasonal water supply, namely the mean WP function (slope = 19.3 kg ha−1 mm−1; x-intercept = 100 mm), proved to be a robust benchmark for maize WP when compared with actual yield and water supply data. Average farmer's WP in central Nebraska was ∼73% of the WP derived from the slope of the mean WP function. A substantial number of fields (55% of total) had water supply in excess of that required to achieve yield potential (900 mm). Pivot irrigation (instead of surface irrigation) and conservation tillage in fields under soybean–maize rotation had the greatest IWUE and yield. Applied irrigation was 41 and 20% less under pivot and conservation tillage than under surface irrigation and conventional tillage, respectively. Simulation analysis showed that up to 32% of the annual water volume allocated to irrigated maize in the region could be saved with little yield penalty, by switching current surface systems to pivot, improving irrigation schedules to be more synchronous with crop water requirements and, as a fine-tune option, adopting limited irrigation.  相似文献   

9.
Four two-year field trials, arranged in randomised split-plots, were carried out in southern Sweden with the aim of determining whether reduced N fertiliser dose in winter wheat production with spring under-sown clover cover crops, with or without perennial ryegrass in the seed mixture, would increase the clover biomass and hence the benefits of the cover crops in terms of the effect on the wheat crop, on a subsequent barley crop and on the risk of N leaching. Four doses of nitrogen (0, 60, 120 or 180 kg N ha−1) constituted the main plots and six cover crop treatments the sub-plots. The cover crop treatments were red clover (Trifolium pratense L.), white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.) in pure stands and in mixtures. The winter wheat (Triticum aestivum L.) was harvested in August and the cover crops were ploughed under in November. The risk of N leaching was assessed in November by measuring the content of mineral N in the soil profile (0–30, 30–90 cm). In the following year, the residual effects of the cover crops were investigated in spring barley (Hordeum distichon L.) without additional N. Under-sowing of cover crops did not influence wheat yield, while reduced N fertiliser dose decreased yield and increased the clover content of the cover crops. When N was applied, the mixed cover crops were as effective in depleting soil mineral nitrogen as a pure ryegrass cover crop, while pure clover was less efficient. The clover content at wheat harvest as well as the amount of N incorporated with the cover crops had a positive correlation with barley yield. Spring barley in the unfertilised treatments yielded, on average, 1.9–2.4 Mg DM ha−1 more in treatments with clover cover crops than in the treatment without cover crops. However, this positive effect decreased as the N dose to the preceding wheat crop increased, particularly when the clover was mixed with grass.  相似文献   

10.
Cover cropping can have various beneficial effects to the cropping system such us the increase of soil nutrient content and weed suppression. In this respect, the species used for covering is of great importance. This paper reports results on the yield and weed control effects in potato crops preceded by different cover crops over a 2-year period (2003 and 2004) in Central Italy (Viterbo). Results were obtained in the frame of a more complex study set up in 2002 where in a 3-year chick-pea/potato/tomato rotation, each crop was preceded by 7 different soil managements: 5 cover crops (rapeseed, Italian ryegrass, hairy vetch, snail medick and subclover) + 1 unfertilised weedy fallow (cover crop absent) + 1 control (weedy fallow fertilised with mineral N at a rate of 170 kg ha−1 for potato). Two different weed control regimes in potato were also applied [weed-free crop (1 inter-row hoeing + 1 hilling up + manual weeding on the row); mechanical control (1 inter-row hoeing + 1 hilling up)]. Cover crops were sown in September and cut and ploughed just before potato planting in March. The potato crops following the cover crops were only fertilised with green manure. Averaged over years, all the cover crops produced more above-ground dry biomass than the weedy fallow (4.79 t ha−1 on average vs 2.36 t ha−1). Hairy vetch and subclover accumulated the highest N in the incorporated biomass (169 and 147 kg ha−1), followed by snail medick (108), rapeseed (99), ryegrass (88) and weedy fallow (47). Rapeseed and ryegrass were the most efficient weed suppressors and had the least proportion of weed biomass (<1%) of the total produced by the cover, while they also reduced weed emergence in the following potato crops (8.8 plants m−2vs 25.5 plants m−2 with all other cover crops). Following subclover and hairy vetch the potato crop yield was similar to that obtained by mineral N-P-K fertilisation (48.5 t ha−1 of fresh marketable tubers). Mechanical weed control compared to weed free crop always reduced potato yield and the reduction, averaged over years, was greater in N-P-K mineral fertilised control (−23.6%) and smaller in ryegrass (−7.9%).  相似文献   

11.
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   

12.
Yield under drought for several crops has been established as a linear function of the cumulative water transpired during the growing season. For well-watered crops, however, there are no published data on how the duration of the cropping cycle and plant population affect the relationship between yield and transpiration. We evaluated the relationship between yield and estimated cumulative transpiration (T) or evapotranspiration (ET) for well-watered soybean (Glycine max [L.] Merr.) over a wide range of maturity groups (MG, 00–VI) and population densities (10–100 plants m−2) for 3 years. Daily T was estimated by determining the potential ET for a given day and multiplying this by the fraction of radiation intercepted by the crop, and a crop coefficient. Soil evaporation estimates were also made using an energy-balance approach after first subtracting the amount of radiation intercepted by the canopy. Daily values of T and ET were summed from emergence to R6. For all MG, cumulative T increased linearly with increasing population density (1.30 mm plant−1 m−2), but predicted T at low populations (y intercept) more than quadrupled with increasing maturity, from 121 mm (MG 00) to 584 mm (MG VI). In contrast to the linear increase of yield to cumulative T for crops under drought stress, yield response to cumulative T for fully irrigated soybean differing in maturity was described well by an exponential model, predicting that 90% of the asymptotic yield would be obtained at 444 mm of T. Accounting for differences in harvest index and vapor-pressure deficit during the season among cultivars of differing maturity did not resolve the non-linear response of yield or biomass to cumulative T. These data indicate that for water-replete conditions, decreased T associated with short-season soybean need not result in decreased yield relative to full-season cultivars.  相似文献   

13.
《Field Crops Research》2001,69(3):259-266
Water-use efficiency (WUEDM) is directly related to radiation-use efficiency (RUE) and inversely related to crop conductance (gc). We propose that reduced WUEDM caused by shortage of nitrogen results from a reduction in RUE proportionally greater than the fall in conductance. This hypothesis was tested in irrigated wheat crops grown with contrasting nitrogen supply; treatments were 0, 80 and 120 kg N ha−1 in 1998 and 0, 80, 120 and 160 kg N ha−1 in 1999. We measured shoot dry matter, yield, intercepted solar radiation and soil water balance components. From these measurements, we derived actual evapotranspiration (ET), soil evaporation and transpiration, WUEDM (slope of the regression between dry matter and ET), WUEY (ratio between grain yield and ET), RUE (slope of the regression between dry matter and intercepted radiation), and gc (slope of the regression between transpiration and intercepted radiation). Yield increased from 2.3 in unfertilised to an average 4.7 t ha−1 in fertilised crops, seasonal ET from 311 to 387 mm, WUEDM from 23 to 37 kg ha−1 mm−1, WUEY from 7.6 to 12.4 kg ha−1 mm−1, RUE from 0.85 to 1.07 g MJ−1, while the fraction of ET accounted for soil evaporation decreased from 0.20 to 0.11. In agreement with our hypothesis, RUE accounted for 60% of the variation in WUEDM, whereas crop conductance was largely unaffected by nitrogen supply. A greater fraction of evapotranspiration lost as soil evaporation also contributed to the lower WUEDM of unfertilised crops.  相似文献   

14.
The concept of aerobic culture is to save water resource while maintaining high productivity in irrigated rice ecosystem. This study compared nitrogen (N) accumulation and radiation use efficiency (RUE) in the biomass production of rice crops in aerobic and flooded cultures. The total water input was 800–1300 mm and 1500–3500 mm in aerobic culture and flooded culture, respectively, and four high-yielding rice cultivars were grown with a high rate of N application (180 kg N ha−1) at two sites (Tokyo and Osaka) in Japan in 2007 and 2008. The aboveground biomass and N accumulation at maturity were significantly higher in aerobic culture (17.2–18.5 t ha−1 and 194–233  kg N ha−1, respectively) than in flooded culture (14.7–15.8 t ha−1 and 142–173 kg N ha−1) except in Tokyo in 2007, where the surface soil moisture content frequently declined. The crop maintained higher N uptake in aerobic culture than in flooded culture, because in aerobic culture there was a higher N accumulation rate in the reproductive stage. RUE in aerobic culture was comparable to, or higher than, that in flooded culture (1.27–1.50 g MJ−1 vs. 1.20–1.37 g MJ−1), except in Tokyo in 2007 (1.30 g MJ−1 vs. 1.37 g MJ−1). These results suggest that higher biomass production in aerobic culture was attributable to greater N accumulation, leading to higher N concentration (N%) than in flooded culture. Cultivar differences in response to water regimes were thought to reflect differences in mainly (1) early vigor and RUE under temporary declines in soil moisture in aerobic culture and (2) the ability to maintain high N% in flooded culture.  相似文献   

15.
Plant responses to water deficit need to be monitored for producing a profitable crop as water deficit is a major constraint on crop yield. The objective of this study was to evaluate physiological responses of cotton (Gossypium hirsutum) to various environmental conditions under limited water availability using commercially available varieties grown in South Texas. Soil moisture and variables of leaf gas exchange were measured to monitor water deficit for various varieties under different irrigation treatments. Lint yield and growth variables were also measured and correlations among growth parameters of interest were investigated. Significant differences were found in soil moisture, leaf net assimilation (An), stomatal conductance (g), transpiration rate (Tr), and instantaneous water use efficiency (WUEi) among irrigation treatments in 2006 while no significant differences were found in these parameters in 2007. Some leaf gas exchange parameters, e.g., Tr, and leaf temperature (TL) have strong correlations with An and g. An and WUE were increased by 30–35% and 30–40%, respectively, at 600 μmol (CO2) m−2 s−1 in comparison with 400 μmol (CO2) m−2 s−1. Lint yield was strongly correlated with g, Tr, WUE, and soil moisture at 60 cm depth. Relative An, Tr, and TL started to decrease from FTSW 0.3 at 60 cm and FTSW 0.2 at 40 cm. The results demonstrate that plant water status under limited irrigation management can be qualitatively monitored using the measures of soil moisture as well as leaf gas exchange, which in turn can be useful for describing yield reduction due to water deficit. We found that using normalized An, Tr, and TL is feasible to quantify plant water deficit.  相似文献   

16.
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   

17.
Cereal–legume intercrops are gaining increasing interest in Europe. Modelling, by taking into account the complexity of species interactions, can be a very useful tool to study such systems and to test new strategies in various soil and climatic conditions. The present work describes the adaptation of an intercrop model for pea–barley intercrops through the extrapolation of the STICS sole crop model and its parameterisation from experimental data recorded on sole crops. Several improvements have been added to the existing crop model to allow an inversion of dominance in height between species during the crop cycle and a trophic link between crop growth rate and the potential for N2 fixation. A 2-year dataset on pea and barley sole crops grown under non-limiting water conditions and with full crop protection was first used for calibration. The intercrop model was subsequently tested on experimental datasets of pea–barley intercrops grown under the same conditions as the sole crops. The intercrop experiments used to test the intercrop model differed in soil type, soil N supply and plant densities of each species.  相似文献   

18.
Poor yields of East African highland bananas (Musa spp., AAA-EAHB) on smallholder farms have often been attributed to problems of poor soil fertility. We measured the effects of mineral fertilizers on crop performance at two sites over two to three crop cycles; Kawanda in central Uganda and Ntungamo in southwest Uganda. Fertilizers were applied at rates of 0N–50P–600K, 150N–50P–600K, 400N–0P–600K, 400N–50P–0K, 400N–50P–250K and 400N–50P–600K kg ha−1 yr−1. In addition 60Mg–6Zn–0.5Mo–1B kg ha−1 yr−1 was applied to all treatments, with the exception of the control plots which received no fertilizer. Fresh bunch mass and yield increased with successive cycles. Yield increases above the control ranged from 3.1 to 6.2 kg bunch−1 (average bunch weight for all treatments 11.5 kg bunch−1) and 2.2–11.2 Mg ha−1 yr−1 (average yield for all treatments 15.8 Mg ha−1 yr−1) at Kawanda, compared with 12.4–16.0 kg bunch−1 (average bunch weight for all treatments 14.7 kg bunch−1) and 7.0–29.5 Mg ha−1 yr−1 (average yield for all treatments 17.9 Mg ha−1 yr−1) at Ntungamo. The limiting nutrients at both sites were in the order K > P > N. Potassium, N and P foliar nutrient mass fractions were below previously established Diagnosis and Recommendation Integrated System (DRIS) norms, with the smallest K mass fractions observed in the best yielding plots at Ntungamo. Total nutrient uptakes (K > N > P) were higher at Ntungamo as compared with Kawanda, probably due to better soil moisture availability and root exploration of the soil. Average N, P and K conversion efficiencies for two crop cycles at both sites amounted to 49.2 kg finger DM kg−1 N, 587 kg finger DM kg−1 P and 10.8 kg finger DM kg−1 K. Calibration results of the model QUEFTS using data from Ntungamo were reasonable (R2 = 0.57, RMSE = 648 kg ha−1). Using the measured soil chemical properties and yield data from an experiment at Mbarara in southwest Uganda, the calibrated QUEFTS model predicted yields well (R2 = 0.68, RMSE = 562 kg ha−1). We conclude that banana yields can be increased by use of mineral fertilizers, but fertilizer recovery efficiencies need to improve substantially before promoting wide-scale adoption.  相似文献   

19.
The holoparasitic weed Orobanche cumana (sunflower broomrape) constrains sunflower (Helianthus annuus) production in many countries. The development of efficient control strategies requires an understanding of the processes underlying the complex environment–host–parasite interrelations. Growth and development of O. cumana and sunflower were quantified under field conditions in southeastern Romania. Sunflower hybrid Florom 350 was sown at two dates, in plots infested with 0, 50, 200 and 1600 viable O. cumana seeds kg−1 dry soil, under low-input (rainfed, low nitrogen supply) and high-input (irrigated, high nitrogen supply) conditions. Sunflower shoot biomass reached peak values of 760–1287 g m−2 between the end of anthesis and physiological maturity. Seed yield varied from 221 to 446 g m−2. Sunflower biomass and yield were affected by all experimental factors. Seed yield responded positively to delaying sowing from early April to late May as well as to irrigation and fertilisation, and negatively to O. cumana infestation. Yield reductions, which were a product of reduced seed number and size, amounted to 13%, 25% and 37% at parasite seed densities of 50, 200 and 1600 viable seeds kg−1 soil, respectively. Maximum O. cumana attachment numbers, recorded in late-sown high-input crops in 2004, ranged from 11 m−2 in plots with 50 parasite seeds kg−1 soil to 188 m−2 with 1600 seeds kg−1 soil. Parasite attachment number was a function of crop sowing date, water and nutrient supply, seedbank density, and sunflower biomass and root length density, via mechanisms of parasite seed stimulation, host carrying capacity and intraspecific competition. Delayed sowing and improved water and nitrogen supply were associated with increases in parasite number that neutralised yield-boosting effects of irrigation and fertilisation at the highest infestation level. Sunflower shoot biomass was significantly reduced by O. cumana infection, with reductions affecting organs in the order head > stem > leaves. Most of the discrepancy between infected and non-infected plants was accounted for by O. cumana biomass. Parasites mainly acted as an extra sink for assimilates during sunflower generative growth and impaired host photosynthesis to a much lesser degree. Results suggest that similar mechanisms govern infection level and host–parasite biomass partitioning across different Orobanche–host systems.  相似文献   

20.
Banana is the primary food crop in Uganda, but yields are low due to a complex of abiotic and biotic constraints. However, quantitative information on the importance, interactions, and geographic distribution of yields and constraints is scanty. We monitored yields, biotic and abiotic constraints in 159 plots in Central, South and Southwest Uganda in 2006–2007. About half the plots were on-farm demonstrations that received fertilizer (average 71N, 8P, 32 K kg ha−1 year−1) through a development project, the rest were ordinary farmer fields (i.e. controls). Fresh banana yields in controls were significantly (P ≤ 0.05) higher in Southwest (20 t ha−1 year−1) compared with Central (12 t ha−1 year−1) and South (10 t ha−1 year−1). Demonstrations yielded 3–10 t ha−1 year−1 more than controls. Yield losses were calculated using the boundary line approach. In Central, yield losses, expressed as percentage of attainable yield, were mainly attributed to pests (nematodes 10% loss, weevils – 6%) and suboptimal crop management (mulch 25%). In South, poor soil quality (pH – 21%, SOM – 13%, N-total – 13%, and Clay – 11%) and suboptimal crop management (weeds – 20%) were the main constraints. In Southwest, suboptimal crop management (mulch 16%), poor soil quality (K/(Ca + Mg) − 11%) and low rainfall (5%) were the primary constraints. The study revealed that biotic stresses (i.e. pests, weeds) are particularly important in Central, whereas abiotic stresses (i.e. nutrient deficiencies, drought) dominate in South and Southwest. This study concludes that (i) technologies currently available allow farmers to double yields and (ii) past research efforts have mistakenly neglected abiotic constraints.  相似文献   

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