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1.
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
2.
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
3.
A field experiment was carried out on maize ( Zea mays, L.) to study the effects of different fertilizer management on nitrogen status in soil and plant response. Three different fertilizers, mineral (MN), mineral plus buffalo manure (MN + BM) and organo-mineral with peat (OMP), were added at the usual (140, 61 and 116 kg ha −1) and the reduced (70, 31 and 58 kg ha −1) rates of N, P and K. respectively. Soil samples were analyzed for N by both the Kjeldahl method and the electro-ultrafiltration technique (EUF). The soil Kjeldahl-N concentrations were scarcely affected by the different fertilizer treatments, while the EUF-N concentrations were closely correlated with the amounts of N added. The EUF also discriminated between the NO 3-N and the sum of the ammonium and the easily extractable organic N forms (EUF-N org + NH 4). The largest proportions of EUF-Norg + NH 4 were found in the untreated plots and in the plots treated with buffalo manure. The different fertilizer treatments significantly affected grain yield, which ranged from a minimum of 6.3 t ha −1 from the untreated plots, to a maximum of 11.9 t ha −1 from those supplied with 140 kg N, 61 kg P and 116 kg K ha −1 by OMP fertilizer. The highest agronomic efficiency index for N was exhibited in the OMP treatment at the reduced rate. The grain yield was closely correlated with the total extractable EUF-N, but different relationships were found between the rate of N added, the level of EUF-NO,-N in soil and grain yield for the different fertilizer treatments. 相似文献
4.
A field study was conducted to assess the effect of N fertilizer application to wheat ( Triticum aestivum L.), tillage system and crop rotation on total denitrification N losses, N 2O and CO 2 emissions under Mediterranean conditions in a long-term trial started 18 years ago on a Vertisol soil. The tillage system consisted of conventional tillage vs. no-tillage and the crop rotation system consisted of two different 2-years rotations: wheat–sunflower ( Helianthus annuus L.) (WS) and wheat–faba bean ( Vicia faba L.) (WF). Fertilizer rates were 0 and 100 kg N ha −1 applied to wheat splitted in two amendments of 50 kg N ha −1 each. Two different fertilization systems were studied. In the old fertilized plots system fertilizer had been applied for 18 years since the beginning of the trial, and in the new fertilized plots system fertilizer was applied for the first time when this experiment was started. Measurements were carried out after fertilizer applications. In the long term, continued fertilizer application produced a higher soil total N content. Nevertheless, no increase in denitrification potential, N2O + N2 production by denitrification, N2O or CO2 emissions was observed either by the recent application of N or by the continued application during 18 years. The soil presented a higher potential to denitrify up to N2 than up to N2O. So, denitrification was probably occurring mainly in the form of N2, while N2O emissions were occurring in a great manner by nitrification, both denitrification and nitrification occurring simultaneously at soil field capacity (60–70%) expressed as water filled pore space (WFPS). Conventional tillage induced an increase in soil total N content and in the potential to denitrify up to N2 with respect to no-tillage. This higher potential was translated into higher N2O + N2 production by denitrification presumably stimulated in the short time by the higher available carbon provided by decomposing roots and by the subsequent creation of soil anaerobic microsites. Contrarily, no effect of tillage was observed on N2O emissions because of being produced in an important manner by nitrification, which does not depend on carbon availability. The wheat–faba bean rotation induced higher soil nitrate contents than the wheat–sunflower, although the effect in the long time was not observed regarding soil total N content. The same as for the fertilizer effect, this increase in nitrate content was not followed by a higher denitrification potential or higher N2O + N2 production by denitrification because of the lack of organic matter, while an increase was observed in N2O emissions. 相似文献
5.
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
6.
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 m 3 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 NO 3−-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 m 3 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 m 3 ha −1 of PS, 200 kg ha −1of mineral N), respectively. All years average soil NO 3−-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 m 3 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 NO 3−-N content before planting. For this reason, soil NO 3−-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 NO 3−-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
7.
Winter wheat was grown in three field experiments, each repeated over two or three seasons, to investigate effects of extending flag leaf life by fungicide application on the concentration, kg ha −1 and mg grain −1 of nitrogen (N) and sulphur (S) as well as N:S ratio and sodium dodecyl sulphate (SDS) sedimentation volume. The experiments involved up to six cultivars and different application rates, timings and frequencies of azoxystrobin and epoxiconazole. For every day the duration to 37% green flag leaf area ( m) was extended, N yield was increased by 2.58 kg ha −1, N per grain by 0.00957 mg, S yield by 0.186 kg ha −1 and S per grain by 0.000718 mg. The N:S ratio decreased by 0.0135 per day. There was no evidence that these responses varied with cultivar. In contrast, the relationship between flag leaf life and N or S concentration interacted with cultivar. The N and S concentrations of Shamrock, the cultivar that suffered most from brown rust ( Puccinia recondita), increased with the extension of flag leaf life whereas the concentrations of N and S in Malacca, a cultivar more susceptible to Septoria tritici, decreased as flag leaf senescence was delayed. This was because the relationships between m and N and S yields were much better conserved over cultivars than those between m and thousand grain weight (TGW) and grain yield ha −1. 相似文献
8.
Grain legumes, especially peas, could play a key role in organic cropping systems. They could provide nitrogen (N) to the system via N 2 fixation and produce grain rich in protein while improving soil N for the succeeding crop. Thus, maximising N 2 fixation and optimising grain N production together with N contribution to soil is a challenging issue for organic pea crops. However, pest, disease and weed infestation are less easy to control in organic systems than in conventional systems. Therefore, the effects of weed infestation and pea weevil ( Sitona lineatus L.) attacks on N nutrition and N 2 fixation of organic pea crops were examined by on-farm monitoring over two years. The magnitude of the net contribution of the crops to the soil N balance in relation to their productivity was also assessed. In many situations, weed infestation together with pea weevil damage severely limited the nitrogen nutrition and grain yield. Percentage of N derived from fixation (%Ndfa) increased with weed biomass because weeds appeared more competitive than peas for soil N. But %Ndfa decreased with pea weevil leaf damage score. The interaction between these two biotic factors affected N yields and the net contribution of the crops to soil N. This latter ranged from −133 kg N ha −1 to 69 kg N ha −1 depending on %Ndfa and nitrogen harvest index (NHI). Optimising both grain N and net balance would require a reduction in root nodule damage by weevil larvae in order to maximise %Ndfa and a reduction in the NHI through the choice of cultivar and/or suitable crop management. 相似文献
9.
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
10.
Rain fed crop production in Mediterranean environments depends to a large extent on strategies that avoid the intense summer drought. Early plantings of sunflower have given consistently higher yields in such environments, but the basis for such yield increases has not been explored. We conducted two field experiments at Cordoba (Spain) to investigate the effects of an early and a late planting date on the components of water-limited crop productivity; namely, water use ( T), water use efficiency (TE) and harvest index (HI) of sunflower. The results were generalized by simulating rain fed sunflower yields, under early (1 January) and late (15 March) plantings, for a 25-year period with the aid of a simulation model of the Ceres type (OILCROP-SUN) which has been validated in Cordoba. Experimental seed yields of early plantings in 1989 and 1996 were 2.0 and 3.0 t ha −1, while late plantings yields were 1.3 and 2.4 t ha −1, for the 2 years. Average simulated yields were 2.7 ± 1.1 and 1.9 ± 0.7 t ha −1 for early and late plantings, respectively. For the 2 years, T of early plantings was higher than that of late plantings, but the response of TE and HI to planting date was not the same in the two experiments. In the simulation exercise, T and TE of early plantings were consistently higher than those of late plantings, while there were no differences in the HI for the two planting dates. We conclude that early plantings of sunflower increase rain fed yields by increasing both T and TE, while the impact of planting date on HI very much depends on the crop water stress pattern, which is quite variable from year to year even in the predictable Mediterranean environment. 相似文献
11.
Recently, corn ( Zea mays L.) hybrids accumulating more leaf area above the ear, maturing earlier, yielding better in narrower row spacings and tolerating higher population densities than conventional hybrids have been developed. However, no research has been conducted to assess their ability to compete with weeds. The objective of this study was to quantify morphological and grain yield responses of hybrids with differing canopy architectures to the presence and absence of weeds. Field experiments were conducted in 1996, 1997, and 1998 at Ste. Anne de Bellevue, Quebec and in 1996 at Ottawa, Ontario. Three hybrids, leafy reduced-stature (LRS), late maturing big leaf (LMBL), and conventional Pioneer 3979 (P3979), were evaluated at two population densities (normal and high), row spacings (38 and 76 cm) and weed pressure levels (weed-free and weedy). Weed pressure reduced the plant height of LRS less (only 4 cm) than the tall hybrids (average reduction of 26 cm). The overall grain yield of the LMBL hybrid was much greater (12.7 mg ha −1) than the LRS (9.6 mg ha −1) and P3979 (11.0 mg ha −1) hybrids in the absence, but not in the presence (LRS, 6.5; LMBL, 6.7; and P3979, 6.8 mg ha −1), of weeds. The yield of early-maturing LRS and P3979 (especially LRS) hybrids, were least affected by weed pressure, suggesting better tolerance of, and competition with, weeds. However, further research with more LRS hybrids is needed, as is the development of better yielding LRS hybrids, before they can be recommended over conventional hybrids. 相似文献
12.
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
13.
The present study was conducted to investigate the possible interactive effects of rising atmospheric CO 2 concentration [CO 2] and drought stress on water use of wheat. Spring wheat ( Triticum aestivum cv. “Minaret”) was grown either in 1 m diameter lysimeters with 0.4 m soil depth (1998) or in the field (1999) in open-top chambers under two CO 2-concentrations (ambient, ambient + 280 ppm) and two watering regimes (well-watered = WW with a plant available water content PAW > 40 mm and drought stressed = DS, 10 mm < PAW < 30 mm) beginning after first node stage. Canopy evapotranspiration ( EC) was measured continuously from first the node stage until the beginning of flag leaf senescence using four open-system canopy chambers (0.78 m 3). Seasonal changes of the absorption of photosynthetically active radiation (APAR) of the canopy and root growth (1999) were also measured. In both growing seasons leaf area index increased in response to elevated [CO2] in both water treatments. The related effects of [CO2] on canopy radiation absorption (APAR) were, however, smaller. EC was linearily related to APAR in both growing seasons. While elevated [CO2] reduced the slope of this relation under WW conditions by ca. 20% in both growing seasons, it was not reduced (1998) and even increased (1999) under drought. Canopy conductance (GC) calculated as EC divided by vapour pressure deficit of air, showed a non-linear relationship to APAR that was best explained by saturation curves. Under WW conditions, elevated [CO2] reduced the initial slope of GC versus APAR as well as GC at saturating light conditions (ca. −30%), while under DS conditions no effect of elevated [CO2] could be detected. Under high light conditions (PAR > 400 μmol m−2 s−1) a critical “threshold value” of PAW (TPAW, ca. 40 mm) could be identified above which GC did not respond to PAW. While in 1998 GC did not respond to elevated [CO2] at PAW < TPAW, it was slightly increased at low PAW values in the field experiments of 1999. The reduction of TPAW by elevated [CO2] may be explained by enhanced root growth (1999) that would have given the plants better access to soil water resources. The present results suggest that below a critical soil water content elevated [CO2] will not reduce canopy water loss of wheat or may even enhance it. 相似文献
14.
This paper reviews current knowledge regarding the influence of plant density on the growth and yield of the faba bean crop ( Vicia faba L.). An analysis is also made of sowing rate and other factors that may modify optimum plant density, including environmental conditions; in this sense, should be made a differentiation between faba crops grown in temperate conditions and those grown in Mediterranean and semi-arid conditions. The genotype also prompts variations in optimum plant density, depending on the botanical type ( mayor, equina or minor) and the growth habit (determinate versus indeterminate) of the cultivar selected. Sowing date also influences optimum seeding rate, which is lower for autumn–winter sowing under temperate and Mediterranean conditions and increases as the sowing date is delayed. For the spring-sown crops typical of temperate conditions, optimum plant density will be higher due to the shorter growing season. With a longer growing season and under optimum environmental conditions, there is normally no additional response to densities over 20 plants m −2, while in suboptimal conditions, optimum plant density may increase to over 60 plants m −2. Although the faba bean crop displays considerable plasticity in response to variations in plant density, mainly with regard to number of pods per square meter, it is not wholly clear to which component of yield this should really be ascribed. Number of stems per plant appears to be the most influential factor, although further research is required to confirm this. 相似文献
15.
Wheat and barley yields from three farms in the Ebro river valley are shown to be strongly dependent on seasonal rainfall, particularly that during November-January and March-May of the cropping season. In the driest farm, in Monegrillo, Zaragoza province (seasonal rainfall, 251 mm), yields increased by c. 5.9 (wheat) and 9.4 (barley) kg ha −1 per mm of extra rain during the entire cropping season, taken as October-May inclusive. The other farms, at El Canós and Selvanera in Lleida province, had seasonal rainfalls of 364 and 334 mm, and yields of barley increased by 4.3 and 9.0 kg ha −1, respectively, per mm of extra rain in the cropping season, taken as September to May inclusive. In Monegrillo, cereals are grown in a cereal-fallow rotation. Normal fallowing (duration 17 months) compared to minimum fallowing (5 months) increased the calculated water content of the top 100 cm of the dominant soils by 19 mm. This extra water was estimated to benefit yield by 7.0% (wheat) and 6.2% (barley), raising the average yields of crops greater than 300 kg ha−1 to 1222 and 1522 kg ha−1, respectively. Agronomic practices in Monegrillo during the fallow should focus on means of increasing the proportion of the rain stored in the profile during the fallow. At all three locations, decreasing water evaporation from the soil during the cropping season would likely benefit yield. 相似文献
16.
In the optimisation of grain yield and quality of wheat, plant distribution is a key factor. In contrast to high yield levels, at moderate levels, widening the row space did not decrease grain yield. To gain information about changes in the quality and yield with changing in row spacings in organic farming systems, experiments were conducted at two locations in the Swiss midlands in 2001/2002. Winter wheat ( Triticum aestivum L., cv. Titlis) was directly drilled in rows 0.1875 and 0.3750 m apart at the same seeding rate per area. An unfertilised treatment and the usual application of 60 m 3 ha −1 liquid farmyard manure were compared. While the grain yield was not decreased by the wider row spacing, the thousand kernel weight (TKW), and grain protein content were increased from 42.6 to 43.5 g and from 11.7 to 12.7%, respectively, compared to the narrow row spacing. Liquid manure, on average of both experimental sites, increased the yield (from 3.725 to 4.765 Mg ha −1) and the grain protein content (from 12.0 to 12.5%). Doubling the space between the rows from 0.1875 to 0.3750 m seemed to be a suitable strategy for managing directly drilled winter wheat in organic farming systems. 相似文献
17.
A study was conducted in controlled environment glasshouses to investigate the effects of soil moisture on resource capture and conversion of three landraces (DipC, S19-3 and UN from Botswana, Namibia and Swaziland, respectively) of bambara groundnut ( Vigna subterranea (L.) Verdc.). The study was conducted under two soil moisture treatments: an irrigated control and a drought treatment where irrigation was withheld from approximately flowering to final harvest. Drought reduced the mean fractional intercepted radiation ( f) from 0.8 to less than 0.7 across landraces. The mean light extinction coefficient (=0.46) was not affected either by landrace or watering regime, while cumulative intercepted radiation ( Sci) reduced under drought because of the reduction in f. Drought reduced total transpiration ( Ec) only in DipC while it had no effect on the other two landraces. Crops under irrigation extracted most of the water from the top 50 cm of the profile while those under drought extracted water down to 90 cm. The conversion coefficient for intercepted radiation ( s; g MJ −1) was reduced by 32%, from 1.51 to 1.02 g MJ −1. Similarly, drought reduced the dry matter/transpired water ratio ( εw; g kg −1) by 20% from 2.05 to 1.65 g kg −1. 相似文献
18.
The effects of N rates and N timings on yield formation, N uptake at five growth stages and fertilizer N use efficiency of six-row and two-row winter barley were evaluated in field trials conducted from 1990/91 to 1992/93 at the TU Munich's research station Roggenstein. On average over 3 years the six-row cultivar yielded most at a total rate of 110 kg ha−1 N including an early application of 40 kg ha−1 N up to EC 30 (Zadoks scale). The two-row cultivar achieved maximum yield at a total rate of 140 kg ha−1 N including early applications of 70 kg ha−1 N up to EC 30. The highest yielding N-treatments of six-row barley regularly took up less nitrogen at EC 32 (95 kg ha−1 N on average) than the non-optimally fertilized treatments, whereas full exploitation of the yield potential of two-row barley was associated with higher rates of N-uptake at EC 32 (113 kg ha−1 N on average). Lodging did not occur in the trials conducted in 1991 and 1992 and no difference was detected between the two cultivars in fertilizer N use efficiency. With six-row barley the N treatment giving maximum yield also led to an optimum fertilizer N use efficiency. Full exploitation of the two-row barley yield potential was associated with suboptimal fertilizer N use efficiencies. 相似文献
19.
In order to evaluate the possibility of reducing energy input in giant reed ( Arundo donax L.) as a perennial biomass crop, a field experiment was carried out from 1996 to 2001 in central Italy. Crop yield response to fertilisation (200–80–200 kg ha −1 N–P–K), harvest time (autumn and winter) and plant density (20,000 and 40,000 plants per ha) was evaluated. The energy balance was assessed considering the energy costs of production inputs and the energy output obtained by the transformation of the final product. The crop yield increased by +50% from the establishment period to the 2nd year of growth when it achieved the highest dry matter yield. The mature crop displayed on average annual production rates of 3 kg dry matter m −2, with maximum values obtained in fertilised plot and during winter harvest time. Fertilisation mainly enhanced dry matter yield in the initial period (+0.7 kg dry matter m−2 as years 1–6 mean value). The biomass water content was affected by harvest time, decreasing by about 10% from autumn to winter. With regard to plant density, higher dry matter yields were achieved with 20,000 plants per ha (+0.3 kg dry matter m−2 as years 1–6 mean value). The total energy input decreased from fertilised (18 GJ ha−1) to not fertilised crops (4 GJ ha−1). The higher energetic input was represented by fertilisation which involved 14 GJ ha−1 (fertilisers plus their distribution) of total energy costs. This value represents 78% of total energy inputs for fertilised crops. Giant reed biomass calorific mean value (i.e., the calorific value obtained from combustion of biomass sample in an adiabatic system) was about 17 MJ kg−1 dry matter and it was not affected by fertilisation, or by plant density or harvest time. Fertilisation enhanced crop biomass yield from 23 to 27 dry tonnes per ha (years 1–6 mean value). This 15% increase was possible with an energy consumption of 70% of the overall energy cost. Maximum energy yield output was 496 GJ ha−1, obtained with 20,000 plants per ha and fertilisation. From the establishment period to 2nd–6th year of growth the energy production efficiency (as ratio between energy output and energy input per ha) and the net energy yield (as difference between energy output and energy input per ha) increased due to the low crop dry biomass yield and the high energy costs for crop planting. The energy production efficiency and net energy yield were also affected by fertilisation and plant density. In the mature crop the energy efficiency was highest without fertilisation both with 20,000 (131 GJ ha−1) and 40,000 plants per ha (119 GJ ha−1). 相似文献
20.
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
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