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1.
Sustainable soil and crop management practices that reduce soil erosion and nitrogen (N) leaching, conserve soil organic matter, and optimize cotton and sorghum yields still remain a challenge. We examined the influence of three tillage practices (no-till, strip till and chisel till), four cover crops {legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secaele cereale L.)], vetch/rye biculture and winter weeds or no cover crop}, and three N fertilization rates (0, 60–65 and 120–130 kg N ha−1) on soil inorganic N content at the 0–30 cm depth and yields and N uptake of cotton (Gossypium hirsutum L.) and sorghum [Sorghum bicolor (L.) Moench]. A field experiment was conducted on Dothan sandy loam (fine-loamy, siliceous, thermic, Plinthic Paleudults) from 1999 to 2002 in Georgia, USA. Nitrogen supplied by cover crops was greater with vetch and vetch/rye biculture than with rye and weeds. Soil inorganic N at the 0–10 and 10–30 cm depths increased with increasing N rate and were greater with vetch than with rye and weeds in April 2000 and 2002. Inorganic N at 0–10 cm was also greater with vetch than with rye in no-till, greater with vetch/rye than with rye and weeds in strip till, and greater with vetch than with rye and weeds in chisel till. In 2000, cotton lint yield and N uptake were greater in no-till with rye or 60 kg N ha−1 than in other treatments, but biomass (stems + leaves) yield and N uptake were greater with vetch and vetch/rye than with rye or weeds, and greater with 60 and 120 than with 0 kg N ha−1. In 2001, sorghum grain yield, biomass yield, and N uptake were greater in strip till and chisel till than in no-till, and greater in vetch and vetch/rye with or without N than in rye and weeds with 0 or 65 kg N ha−1. In 2002, cotton lint yield and N uptake were greater in chisel till, rye and weeds with 0 or 60 kg N ha−1 than in other treatments, but biomass N uptake was greater in vetch/rye with 60 kg N ha−1 than in rye and weeds with 0 or 60 kg N ha−1. Increased N supplied by hairy vetch or 120–130 kg N ha−1 increased soil N availability, sorghum grain yield, cotton and sorghum biomass yields, and N uptake but decreased cotton lint yield and lint N uptake compared with rye, weeds or 0 kg N ha−1. Cotton and sorghum yields and N uptake can be optimized and potentials for soil erosion and N leaching can be reduced by using conservation tillage, such as no-till or strip till, with vetch/rye biculture cover crop and 60–65 kg N ha−1. The results can be applied in regions where cover crops can be grown in the winter to reduce soil erosion and N leaching and where tillage intensity and N fertilization rates can be minimized to reduce the costs of energy requirement for tillage and N fertilization while optimizing crop production.  相似文献   

2.
Maize (Zea mays L.) is a very important crop in many of the irrigated areas of the Ebro Valley (NE Spain). Intensive pig (Sus scrofa domesticus) production is also an important economic activity in these areas, and the use of pig slurry (PS) as a fertiliser for maize is a common practise. From 2002 to 2005, we conducted a field trial with maize in which we compared the application of 0, 30 and 60 m3 ha−1 of PS combined with 0, 100 and 200 kg ha−1 of mineral N at sidedress. Yield, biomass and other related yield parameters differed from year to year and all of them were greatly influenced by soil NO3−-N content before planting and by N (organic and/or mineral) fertilisation. All years average grain yield and biomass at maturity ranged from 9.3 and 18.9 Mg ha−1 (0 PS, 0 mineral N) to 14.4 and 29.6 Mg ha−1 (60 m3 ha−1 of PS, 200 kg ha−1of mineral N), respectively. Grain and total N biomass uptake average of the studied period ranged from 101 and 155 kg ha−1 (0 PS, 0 mineral N) to 180 and 308 kg ha−1 (60 m3 ha−1 of PS, 200 kg ha−1of mineral N), respectively. All years average soil NO3−-N content before planting and after harvest were very high, and ranged from 138 and 75 kg ha−1 (0 PS, 0 mineral N) to 367 and 457 kg ha−1 (60 m3 ha−1 of PS, 200 kg ha−1of mineral N), respectively. The optimal N (organic and/or mineral) rate varied depending on the year and was influenced by the soil NO3−-N content before planting. For this reason, soil NO3−-N content before planting should be taken into account in order to improve N fertilisation recommendations. Moreover, the annual optimal N rates also gave the lowest soil NO3−-N contents after harvest and the lowest N losses, as a consequence they also could be considered as the most environmentally friendly N rates.  相似文献   

3.
Although a high biomass yield is obtained from established Miscanthus crops, previous studies have shown that fertilizer requirements are relatively low. As little information on the role of the Miscanthus roots in nutrient acquisition is available, a study was conducted to gather data on the Miscanthus root system and root nutrient content. Therefore in 1992, the root distribution pattern of an established Miscanthus crop was measured in field trials using the trench profile and the auger methods. Also, in 1994/1995, seasonal changes in root length density (RLD) and root nutrient content were monitored three times during the vegetation period.

The trench profile method showed that roots were present to the maximum depth measured of 250 cm. The top soil (0–30 cm) contained 28% of root biomass, while nearly half of the total roots were present in soil layers deeper than 90 cm. Using the auger method, we found that RLD values in the topsoil decreased with increasing distance from the centre of the plants. Below 30 cm, RLD decreased markedly, and differences in root length in the soil between plants were less pronounced. The total root dry weight down to 180 cm tended to increase from May 1994 (10.6 t ha−1) to November 1994 (13.9 t ha−1) and then decreased again until March 1995 (11.5 t ha−1). Nutrient concentrations in the roots decreased with increasing depth. The concentrations of N (0.7–1.4%) and K (0.6–1.2%) were clearly higher than those of P (0.06–0.17%). The mean values for N, P and K contents of the roots of all three sampling dates in 1994/1995 were 109.2 kg N ha−1, 10.6 kg P ha−1 and 92.5 kg K ha−1.

Although our results showed that RLD values for Miscanthus in the topsoil are lower than for annual crops, the greater rooting depth and the higher RLD of Miscanthus in the subsoil mean that nutrient uptake from the subsoil is potentially greater. This enables Miscanthus crops to overcome periods of low nutrient (and water) availability especially during periods of rapid above-ground biomass growth.  相似文献   


4.
The residual effect of 2-year-old swards of clover-ryegrass mixture and ryegrass in monoculture on yield and N uptake in a subsequent winter wheat crop was investigated by use of the 15N dilution method and by mathematical modelling. The amount of N in the wheat crop, derived from clover-ryegrass residues was 25–43% greater than that derived from residues of ryegrass which had been growing in monoculture. Expressed in absolute values, the N uptake in the subsequent winter wheat crop was 23–28 kg N ha −1 greater after clover-ryegrass mixture than after ryegrass in monoculture. Up to about 54 kg N ha−1 of the N mineralised from the clover-ryegrass crop was calculated to be leached, whereas only 11 kg N ha−1 was leached following ryegrass in monoculture.  相似文献   

5.
This paper describes a methodology for analysing management strategies to find best agronomic practices using a crop simulation model (CERES-Wheat). The study area is the estate of Imperial College at Wye, in the Stour Catchment, Kent, UK, an area highly suited to winter wheat production. The model is validated using historic crop performance data. Yield responses to differing sowing rates (range 200–450 seeds m−2), sowing dates and rates of nitrogen application (between 100 and 220 kg ha−1) with soil types of medium to heavy texture were simulated under water-limited conditions using historical daily weather data. In model validation, observed yields ranged between 6.9 and 7.4 t ha−1, while simulated ranges were between 6.9 and 7.8 ha−1. The RSMD of the difference was small (0.24 t ha−1) and non-significant. Optimum management practices (in terms of planting date, seed density and nitrogen application) were thereby defined. Also, simulations of potential yield (i.e. yield with no water and nutrient stress) were run for comparison. Results of this study reveal that the calibrated and validated CERES-Wheat model can be successfully used for the prediction of wheat growth and yield under conditions appropriate to Western Europe.  相似文献   

6.
The influence of crop density on the remobilization of dry matter and nitrogen from vegetative plant parts to the developing grain, was investigated in the durum wheat (Triticum durum Desf.) varieties Creso, Simeto and Svevo cultivated in the field at three seeding rates, 200, 250 and 400 seeds m−2. Variety × seeding rate interaction was unsignificant for all recorded characters. Grain yield declined in the order Svevo > Simeto > Creso. Yield differences mainly depended on the different number of kernels per unit land and, secondly, on mean kernel weight. Spike components differed among varieties: Svevo and Simeto showed more kernels per spikelet and Creso more spikelets per spike. Grain yield was highest with 400 seeds m−2 primarily due to the higher number of spikes per unit area, and secondly, to the higher mean kernel weight. Post-heading dry matter accumulation was highest in Svevo and lowest in Creso, but varieties showed a reverse order for dry matter remobilization and contribution of dry matter remobilization to grain yield. The increase of seeding rate increased both the post-heading dry matter accumulation and the dry matter remobilization from vegetative plant parts to grain. Nitrogen uptake of the whole crop and N content of grain was higher in Simeto and Svevo than in Creso. The N concentration of grain did not vary among varieties, but Svevo showed a markedly lower N concentration and N content of culms at maturity, which may be consequence of the high N remobilization efficiency performed by this variety. The N uptake by the crop was highest with 400 seeds m−2, but the N concentration of culms, leaves and even grain was slightly lower than with the lower seed rates. The post-heading N accumulation was by far higher in Simeto and Svevo than in Creso, whereas remobilization was highest in Svevo and lowest in Simeto. The percentage contribution of N remobilization to grain N was by far higher in Creso than in the other two varieties. Post-heading N accumulation and N remobilization were highest with the highest plant density, but the contribution of N remobilization to N grain content did not differ between seeding rates.  相似文献   

7.
Information about the effect of the cropping history on the seed yield of oil-seed rape is extremely scarce. In 1992/93 and 1994/95, the effects of different preceding crop combinations (winter barley and winter wheat as preceding crops, oil-seed rape and wheat as pre-preceding crops) on the yield of six double low oil-seed rape cultivars were examined in a field trial at Hohenschulen Experimental Farm, north-west Germany. In addition, eight nitrogen treatments (different amounts and distribution patterns) were tested for their potential to reduce negative effects of the preceding crops. Following the cropping sequence of oil-seed rape then wheat, oil-seed rape yielded only 3.12 t ha−1; after oil-seed rape then barley, the yield was 3.43 t ha−1 compared with 3.77 t ha−1 following wheat then barley and 3.71 t ha−1 following wheat then wheat. The number of seeds per m2 showed a similar pattern, whereas the thousand-seed weight partly compensated for the reduced seed number. It was highest if oil-seed rape was grown 2 years previously. The cultivars differed significantly in their yield potential. Express (3.79 t ha−1) yielded 0.6 t ha−1 more than Falcon (3.18 t ha−1). Increasing amounts of fertilizer-N (80–200 kg N ha−1) increased the seed yield from 3.21 t ha−1 to 3.84 t ha−1. Changes in the distribution pattern within one fertilizer amount had no effect on seed yield. In addition, no interactions between preceding crop combination and the different cultivars or N treatments occurred. It is concluded that crop management cannot totally eliminate the negative effects of an unfavourable cropping history on the seed yield of oil-seed rape.  相似文献   

8.
New high yielding early maturing cultivars of lupins have been introduced in north-west Europe as grain protein crops in crop rotations. This paper reports on a comparative study of lupins with peas and oats, and of their effect on yield of subsequent winter barley crops. These crops were given five levels of N under irrigated and non-irrigated conditions on sand and loam. Under rain fed conditions the grain yield of pea, oat and lupin varied between 24–36, 34–53 and 18–37 hkg DM ha−1, respectively. Supplemental irrigation raised grain yield of oat to 50–60 hkg DM ha−1, while grain yield in pea was not affected and grain yield in lupin in most cases decreased due to gray mould attack and excessive vegetative growth in the indeterminate lupin variety. Under rain fed conditions, the grain nitrogen content of pea, oat and lupin varied between 137–172, 61–80 and 189–226 kg N ha−1, respectively, and was significantly higher in lupin as compared with pea. On sandy soil, similar low-root densities were found for pea, oat and lupin below 30 cm depth. On sand, at final harvest the residual soil-N of lupin and pea, as measured in a subsequent winter barley crop not supplied with N fertilizer, was 15 and 8–10 kg N ha−1 higher than in winter barley following oat, respectively. The nature of the probably more N-root residues of lupin is discussed. On loam, the residual N of lupin and pea was similar, 18–27 kg N ha−1. On sand, under rain fed conditions preceding lupin and pea as compared with oat, increased the barley grain yield at zero N-application 77 and 49%, respectively; the effect of lupin was significantly higher than that of pea until the highest N-level 120 kg N-application ha−1. On loam under rain fed conditions preceding lupin and pea increased the barley grain yield at zero N-application by 36 and 62%, respectively, as compared with oat; at N-application>60 kg N ha−1 the grain yield was similar after all three crops. For both soil types the same level of effect was found under irrigated conditions. Conclusions: Supplemental irrigation might result in lower grain yield in lupin due to gray mould attack and excessive growth if indeterminate lupin varieties are used. Grain nitrogen yield of lupin is significantly higher than that of pea. On sand, the effect of lupin on the subsequent winter barley grain yield is significantly higher than that of pea, probably due to greater N-root nitrogen residues. On loam, lupin and pea have similar effects on the subsequent winter barley crop.  相似文献   

9.
The growth and production of sweet sorghum [Sorghum bicolor (L.) Moench] crops under semi-arid conditions in the Mediterranean environment of southern Italy are constrained by water stress. The effects of temporary water stress on growth and productivity of sweet sorghum were studied during three seasons at Rutigliano (Bari, Italy). The aim of this research was to evaluate the sensitivity of phenological stages subjected to the same water deficit. In a preliminary study it was observed that stomata closed when pre-dawn leaf water potential (Ψb) became lower than −0.4 MPa. This criterion was used in monitoring plant water status in three different plots: one never stressed and two stressed at different phenological stages (‘leaf’ and ‘stem’) when mainly leaves or stems were growing, respectively. An evaluation of the sensitivity of phenological stages subjected to identical water stress was obtained by comparing the above-ground biomass and WUE of drought crops with those of the well-irrigated crop (up to 32.5 t ha−1 of dry matter and 5.7 g kg−1). The sensitivity was greatest at the early stage (‘leaf’), when a temporary soil water stress reduced the biomass production by up to 30% with respect to the control and WUE was 4.8 g kg−1 (average of three seasons). These results help quantify the effects of water constraints on sweet sorghum productivity. An irrigation strategy based on phenological stage sensitivity is suggested.  相似文献   

10.
The influence of ultraviolet (UV-C) light (1.4–13.7 kJ m−2 at 254 nm) on the quality and microbial populations of fresh-cut watermelon [Citrulus lanatus (Thunb.) Matsum. and Nakai] was investigated and compared to that of common sanitizing solutions used for fresh-cut produce. Dipping cubes in chlorine (40 μL L−1) and ozone (0.4 μL L−1) was not effective in reducing microbial populations and quality was lower in cubes receiving these aqueous treatments compared to UV-irradiated cubes or control. In commercial trials, exposing packaged watermelons cubes to UV-C light at 4.1 kJ m−2 produced >1 log reduction in microbial populations by the end of the product's shelf life without affecting juice leakage, color and, overall visual quality. In further experimentation, lower UV-C dose (1.4 kJ m−2) reduced microbial populations to a lower degree and only when complete surface exposure was ensured. Higher UV-C doses did not show any difference in microbial populations (6.3 kJ m−2) or result in quality deterioration (13.7 kJ m−2). Spray applications of hydrogen peroxide (2%) and chlorine (40 μL L−1), without subsequent removal of excess water, failed to further decrease microbial load of cubes exposed to UV-C light at 4.1 kJ m−2. When properly utilized, UV-C light is the only method tested in this study that could potentially be used for sanitizing fresh-cut watermelon.  相似文献   

11.
Water deficit is an important constraint for wheat yield generation under Mediterranean environments. However, nitrogen (N) availability could limit yield in a more important way than poor water conditions. The aim of the work was to analyze, using the Ceres-Wheat crop simulation model, to what degree N fertilization constitutes a tool for reducing the gap between attainable and potential yield. Firstly, the model was calibrated and validated under a wide range of N and water conditions for the region of the Ebro Valley (NE Spain). Anthesis and maturity date were adequately predicted by the model. Predictions of yield tended to be quite accurate in general, though under severe water deficits precision was lower. We then assessed the gap between attainable and potential yield considering different N availabilities at sowing taking into account a weather database of 17 years for the location of Agramunt (NE Spain), representative of cereal growing conditions of the Mediterranean Catalonia. Potential yield ranged between 3.5 and 8.1 Mg ha−1. Variations in potential yield were explained by the duration of the period from sowing to anthesis and by the level of incident radiation during the period immediately previous to anthesis. Average attainable yield was 1.8 Mg ha−1 for N availability of 50 kgN ha−1; but increased to 2.8 Mg ha−1 for higher N availabilities (100–250 kgN ha−1). In the 25% of the worst years there was no effect of N availability on attainable yield. Increasing N availability beyond 100 kgN ha−1 generated a gain in yield only in 6% of the years. Variations between years in attainable yields were mainly explained by rainfall during the period from sowing to anthesis, whereas differences in attainable yield between N treatments increased with increases in rainfall. The gap between potential yield and attainable yield was higher in years with higher potential yield. On the other hand, the higher the attainable yield, the lower the gap. Thus, the proportion of the yield gap ascribed to N availability varied depending on the conditions of the growing season. In the high-yielding potential years, the main restriction for growth was water shortage, and fertilizing only slightly reduced the gap. Conversely, in rainy years characterized by low potential yields and mild water stresses, N management may constitute a simple tool for effectively reducing yield gap under rain-fed conditions.  相似文献   

12.
Atmospheric sulphur (S) depositions have been decreasing in Europe for the past 20 years. Up to now, there were no evidences of S deficiencies on cut grasslands in Belgium. The effects of S fertilisations together with incremental nitrogen (N) dressings were investigated in Belgium using small plot trials on cut grassland between 2001 and 2003. In 4 cases out of 13, S supply increased dry matter yields on average by 0.8 t ha−1 y−1. Response to S appeared to depend on the site, the year, the N fertilisation level and the soil. Grass S content was significantly increased and N:S ratio decreased by S fertilisation. High N:S ratio (>14) was observed in grasslands without S fertilisation even with a moderate N supply. It is concluded that S deficiency can be feared for cut grassland in Belgium mainly on light textured soils after a wet winter.  相似文献   

13.
Accumulation of sludge-borne copper (Cu) by field-grown maize and its distribution between the different plant organs was studied in detail in a long-term sewage sludge field trial. Since 1974, field plots on a coarse sandy soil have been amended each year with farmyard manure (FYM) at a rate of 10 t dry matter (DM) ha−1 year−1 and with sewage sludge at the two levels of 10 t DM ha−1 year−1 (SS 10) and 100 t DM ha−1 per 2 years (SS 100). All field plots have been cropped annually with maize. In 1993, five replicate plants per treatment were examined at six different growth stages from seedling to grain maturity. Each plant was separated into at least 12 different parts and the Cu content of each was determined. Regarding growth parameters, no visible deleterious effects on plant development due to the different soil treatments could be observed, although the dry matter yield of roots and stalks of SS 100-treated plants was significantly reduced. Significantly increased Cu concentrations of up to 60 mg Cu kg−1 DM in the roots of young SS 100-grown maize plants and of up to 20 mg Cu kg−1 DM in the upper leaves at silage stage were found. No critical Cu amounts were reached in the grains until harvest.  相似文献   

14.
The wide variability and complexity of olive orchards makes it difficult to provide solutions to the numerous management questions using a pure experimental approach. In this paper we calibrate and validate a simple model of olive orchard productivity based on the Radiation-Use Efficiency (RUE) concept of Monteith. A calibration experiment was performed in Cordoba from 1998 to 2001 with drip-irrigated olive trees cv. ‘Arbequina’. Destructive samples of 18 trees and non-destructive measurements on 80 trees were used to determine RUE and dry matter partitioning coefficients. Validation experiments were performed in 18 drip-irrigated orchards of seven locations in Southern Spain, including two cultivars (‘Arbequina’ and ‘Picual’). Average RUE was 0.86 g dry matter (MJ PAR)−1 which is equivalent to 1.56 g glucose (MJ PAR)−1. Aboveground accumulated biomass was allocated equally to fruits and vegetative growth, which in turn was partitioned into 30% for leaves and 70% for stems, branches and trunk. The fraction of oil in fruits was 0.38 which implies that the average ratio oil yield/intercepted PAR, which is an equivalent RUE for oil production (o), is 0.17 g oil (MJ PAR)−1. The prediction of oil yield as the product of 0.17 and total intercepted PAR was tested successfully in the validation experiments (relative RMSE = 0.26). Errors of this simple model were partly due to alternate bearing and partly to a decrease in o as canopy size increases, which deserves further research. The concept of o may be also useful for the evaluation of alternate bearing in olive trees.

Estimated potential carbon sequestration by intensive irrigated olive orchards in Southern Spain was 7 t CO2 ha−1 year−1 which is much higher than that of other agricultural systems in Europe.

The simple model of growth and yield presented herein is the core of a complete model of olive growth and yield and may be useful not only for evaluating productivity at different scales but also for solving different management problems (nutrient requirements, plant protection, etc.)  相似文献   


15.
The effect of six doses of beet vinasse (0, 3, 6, 10, 20 and 40 t ha−1, respectively) on wheat (Triticum aestivum cv. Cajeme) yield in dryland conditions (Guadalquivir Valley, Andalusia, Spain) for 3 years on a Typic Xerofluvent was studied. The results showed that at low doses, beet vinasse is of agricultural interest due mainly to its organic matter concentration. The application of this byproduct to the soil increased soil microbial biomass and mineralization of its organic matter increased NO3−–N concentrations in soil. This caused an increase in grain yield in the three seasons. When the vinasse was applied with high doses, NO3−–N concentrations in soil, soil microbial biomass, soil structure, bulk density, electric conductivity, nutrient uptake, crop yield and grain quality were negatively affected. We assume that the high amounts of monovalent cations, particularly Na+, and of fulvic acids, which had been transported into the soil by the vinasse, destabilized the soil structure. This may have led to anaerobic soil conditions being presumably responsible for restricted N mineralization or even for denitrification. This explains the lower N supply to the crops reflected by the low N concentrations in the leaves of treatments A4 and A5.  相似文献   

16.
Berseem clover (Trifolium alexandrinum L.) is an annual forage crop widely grown in Mediterranean environments. However, there is little information available on the patterns of accumulation and partitioning of assimilate in berseem and how this varies with harvest management, plant ontogeny or is influenced by genotype. Field experiments were conducted in Foggia (Italy) during three growing seasons (1991–92, 1992–93 and 1993–94), with the aim of evaluating the effects of different harvest managements on growth dynamics, forage yield and seed yield of one population of Egyptian (cv. ‘Giza 10’) as well as Italian (cv. ‘Sacromonte’) origin. Cutting treatments were applied at three different plant ages: sixth internode elongation (A), early flowering (B), and uncut control (C). The growth and development of the shoot and root systems were followed by destructive harvests made at about 5-day intervals during 9 weeks in spring in all treatments. Seasonal growth pattern, determined as dry matter accumulation, forage yield and seed production were greatly influenced by harvest management. The maximum value (20.5 g per plant on average) of dry weight was reached at about 250 days after sowing for treatment C. Defoliation induced a decrease of crown and root dry matter, however, as shown by the allometric relationships, the growth of roots and shoots was closely correlated and in most cases, shoot growth was higher than root growth and stem relative growth rate (RGR) was higher than leaf RGR. Berseem clover is a defoliation-tolerant species because after cutting, regrowth was accompanied by higher values of leaf-stem ratio (LSR), RGR and stem elongation rate (SER) than in control plants. The highest value for total forage yield (1.6 Kg m−2) and seed yield (60.5 g m−2) were obtained in treatment B and A, respectively. Plants cut at the sixth internode elongation showed a good seed yield and a small decrease (15%) in total forage yield as regards treatment B. Therefore, treatment A appeared the most favourable for obtaining double utilization (forage and seed yield) in a berseem crop. Berseem plants were greatly influenced by harvest treatments applied, but the response did not vary according to the genetic characteristics of the two cultivars examined.  相似文献   

17.
The aim of this study was to identify the physiological characteristics which may affect the yield of six cool-season grain legume species grown in a water-limited Mediterranean-type climate in Western Australia. The rate of net photosynthesis, stomatal conductance and water relations were measured from flowering to complete leaf senescence in white lupin, chickpea, faba bean, field pea, grass pea and lentil. In irrigated plants, the midday leaf water potential was about −0.6 MPa in all species, while the maximum rate of leaf photosynthesis was 30 μmol m−2 s−1 for chickpea and white lupin, and below 20 μmol m−2 s−1 for the other species. With the development of water deficits, the leaf water potential in rain-fed plants decreased to about −3 MPa in chickpea and lentil and −2 MPa in the other species. Photosynthesis and stomatal conductance decreased markedly as the leaf water potential decreased below −0.9 MPa in all six species, including chickpea and lentil, which showed a high degree of osmotic adjustment. Despite the similarity in water use, restricted to the top 40 cm of soil, and water relations characteristics, yields varied markedly among species. Yields were strongly correlated with early biomass production and early pod development.  相似文献   

18.
Central to the CHanging climate and potential Impacts on Potato yield and quality project (CHIP) was the consideration of the potential impacts of ozone and CO2 on growth and yield of future European Potato crops. Potato crops, cv. Bintje, were exposed to ambient or elevated ozone; targeted daily average, 60 nl l−1 for 8 h, and ambient or elevated CO2; targeted 680 μl l−1 averaged over the full growing season, in open top chambers (OTCs) at six European sites in 1998 and 1999, or to elevated CO2 (550 μl l−1) in Free Air Carbon dioxide Enrichment facilities (FACE) at two sites in both years. Some OTC experiments included 550 μl l−1. Above and below ground biomass were measured at two destructive harvests; at maximum leaf area (MLA) and at final-harvest. Final-harvest fresh weight yields of marketable-size tubers, >35 mm diameter, from ambient conditions ranged from 1 to 12 kg m−2. There was no consistent (P>0.1) CO2×O3 interaction for growth or yield variables at either harvest. No consistent effects of ozone were detected at the maximum-leaf-area harvest. However, at final harvest, ozone had reduced both above-ground biomass and tuber dry weight (P<0.05), particularly of the largest (>50 mm) size class. These yield losses showed linear relationships both with accumulated ozone exposure; AOT40 expressed as nl l−1 h over 40 nl l−1, and with yields from chambered ambient-ozone treatments (P<0.05) but, because of partial confounding between the treatment AOT40s and the ambient-ozone yields in the data, the two relationships were not completely independent. Yields from ambient-ozone treatments, however, explained a significant (P<0.01) amount of the residual variation in ozone effects unexplained by AOT40. When averaged over all experiments, mean dry weights and tuber numbers from both harvests were increased by elevated CO2. Only green leaf number at the MLA harvest was reduced. The CO2 responses varied between sites and years. For marketable-size tubers, this variation was unrelated to variation in ambient-CO2 treatment yields. Yield increases resulting from the 680 μl l−1 and 550 μl l−1 treatments were similar. Thus elevating [CO2] from 550 to 680 μl l−1 was less effective than elevating [CO2] from ambient to 550 μl l−1. On average, CO2 elevation to 680 μl l−1 increased the dry weight of marketable-size tubers by about 17%, which far exceeded the average ozone-induced yield loss of about 5%. The net effect of raising CO2 and O3 concentrations on the European potato crop would be an increase marketable yield.  相似文献   

19.
In sloping areas with high precipitation, planting maize into live winter cover crop sods may help to alleviate the environmental problems associated with clean-tillage production systems of maize. The present study evaluates the performance of silage maize (Zea mays L.) under several cultivation methods: CC (conventional cropping system, i.e., maize was sown into the bare, autumn-ploughed soil); LGS/CK (maize was planted into a living Italian ryegrass (Lolium multiflorum Lam.) sod which was subsequently herbicidally killed); and LGS/MR (similar to LGS/CK, but the ryegrass was mechanically regulated). The research was conducted in the midlands of Switzerland on a fertile sandy loam under humid conditions during three cropping seasons. With 110 kg N ha−1 (fertilizer nitrogen plus mineral nitrogen of the soil at maize planting), the CC system was much more productive than were the LGS/CK and LGS/MR systems in terms of dry matter and nitrogen yields of maize. Increasing the nitrogen supply to 250 kg N ha−1 considerably reduced the yield advantage of CC over the LGS/CK and LGS/MR systems, indicating that nitrogen was the most limiting factor for maize yield in the mulch seeding systems. With 250 kg N ha−1, the LGS/CK and LGS/MR systems produced greater total yields of digestible organic matter (maize plus ryegrass) than did the CC system, whereas the total nitrogen yield was similar for all cropping systems. The whole-shoot concentrations of nitrogen were highest under CC, irrespective of the level of nitrogen supply. With 110 kg N ha−1, concentrations of phosphorus and magnesium were clearly higher for the mulch seeding systems. There were only minor differences among the cropping methods in the concentrations of potassium and calcium in the whole shoot. When 250 kg N ha−1 were applied, there were no significant variations among the cropping systems in the concentrations of minerals. Changes in the botanical composition of the cover crop sod and in the time and method of cover crop control may help to reduce the competition for nitrogen between maize and the living mulch.  相似文献   

20.
Availability of water and nitrogen are key constraints to primary productivity in arid and semiarid ecosystems. Theoretically, plant growth is maximised when all resources are equally limiting. This paper tested the hypothesis that for a given amount of available water, the gap between actual and attainable yield of dryland crops in semiarid southern Australia is inversely proportional to the degree of nitrogen and water co-limitation.

Field and simulation experiments were combined in an analysis involving three steps. Step 1 assessed the capacity of a crop simulation model to estimate yield and its responses to water and nitrogen inputs in the semiarid Mallee region. Step 2 derived a boundary function relating grain yield and water availability using simulations with long-term weather records. Step 3 explored the link between degree of co-limitation and deviations between actual yield and the boundary function. Degree of co-limitation (CWN) was calculated as a function of model-derived nitrogen (NSI) and water stress indices (WSI), i.e. CWN = 1 − |NSI − WSI|. Stress indices range from zero (no stress) to 1 (maximum stress), and CWN tends to 1 when both resources impose constraints of similar magnitude to crop growth.

The field experiment combining locations, seasons and management practices generated a range of grain yield from 0.6 to 3.8 t ha−1. Water availability, i.e. seasonal rainfall plus change in soil water content from sowing to harvest, ranged from 127 to 370 mm. Nitrogen fertiliser varied from nil to 36 kg N ha−1 and inorganic nitrogen in the soil profile at sowing ranged from 29 to 497 kg ha−1. For these ranges of conditions, the relationship between simulated and measured yield was statistically undistinguishable from the y = x function.

A factorial modelling experiment combining sites, seasons, initial soil water content and dose of nitrogen fertiliser was used to derive a boundary function which provided an objective and independent upper limit for the field data. Actual yield was below the boundary function in most cases. The difference between actual and attainable yield was inversely proportional to CWN. This study thus supported the hypothesis that yield and water-use efficiency of water- and nitrogen-stressed crops increase with increasing degree of co-limitation.  相似文献   


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