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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.
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
3.
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
4.
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 m 2 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
5.
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
6.
The long-term effects of undersowing a ryegrass catch crop in cereals was analysed with the FASSET simulation model. The model was tested on a 28-year field experiment with ryegrass catch crops in spring barley. The experiment included treatments with nitrogen (N) fertiliser rates, catch crop use and timing of tillage. The modelled effects of these treatments generally agreed with observations on crop production, soil carbon, soil nitrogen and nitrate leaching. Both the observations and the simulations predicted a yield increase of 7 kg N ha −1 and an increase in nitrate leaching of 13 kg N ha −1 due to a prehistory of 24 years with continuous use of catch crops compared to a prehistory without catch crops. A range of scenarios was constructed to evaluate the fate of the reduced nitrate leaching on crop N uptake, N leaching, gaseous emissions and change in soil organic N, and how this fate interacts with soils and climate and management. These scenarios showed that 22–30% of the reduced nitrate leaching was subsequently leached during the following decades after termination of catch crop use. Between 35 and 40% of the reduced nitrate leaching was harvested in cereals. The exact distribution depended primarily on the soil texture. The scenarios showed that effects of catch crops should be evaluated on the long-term rather than consider short-term effects only. 相似文献
7.
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
8.
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
9.
On a brown warp soil (Fluventic Eutrochrept) near Goettingen, Germany, conventional leafed pea ( Pisum sativum L. cvs Messire and Bohatyr) and semileafless types (cvs Profi, Juno and Azur) were grown in mixed stands together with oat ( Avena sativa cvs Alf and Lutz) in substitutively designed experiments from 1995 to 1997. Oat was the dominant component. Crowding coefficients for oat averaged 7.4. No relationship could be detected between the crowding coefficient of oat and any yield advantage from the mixture. Crowding coefficients for pea varied substantially, between 0.1002 (Juno and Alf in 1996) and 0.2979 (Bohatyr and Alf in 1996). Crowding coefficients for semileafless pea cultivars were smaller than for conventional leafed types. The yield advantage of the mixture increased as the crowding coefficient of pea increased. The maximum yield increase for the mixture was achieved when the relative yield total (RYT)=1.17 or + 11 dt grain DM ha –1 for mixtures of the long-strawed conventional leafed cultivars Bohatyr and Alf (in 1996). The crowding coefficients of pea were positively correlated with the level of symbiotically fixed N 2 in the mixed stands. When N 2 fixation with mixed cropping was about 30 kg N ha –1, RYT was unity. Increasing symbiotic N 2 in the mixtures resulted in increasing yield advantages in the mixture. Short-strawed pea cultivars seem unsuitable for mixing with oat. Plant height of pea appeared to be more important than plant leaf type. Accordingly, mixtures containing the long-strawed semileafless pea cultivars Profi and Alf were more successful. It is concluded that increased competitiveness of the pea component in the mixture with oat entails increasing the level of symbiotic N 2 fixation including resource complementarity and thus yield advantage in the mixed stands. 相似文献
10.
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
11.
The water use ( Et) and water use efficiency ( WUE) of a range of cool season grain legume species (field pea [ Pisum sativum L.], faba bean [ Vicia faba L.], chickpea [ Cicer arietinum L.], lentil [ Lens culinaris Med.], albus lupin [ Lupinus albus L.], dwarf chickling [ Lathyrus cicera L.], ochrus chickling [ Lathyrus ochrus L.], grass pea [ Lathyrus sativus L.], narbon bean [ Vicia narbonensis L.], common vetch [ Vicia sativa L.], and purple vetch [ Vicia benghalensis L.]) were examined on fine textured neutral to alkaline soils in the low to medium rainfall Mediterranean-type environments in south-western Australia at Merredin and Mullewa in two seasons. There was no difference in the total Et between grain legumes at either site in either year. There was also no variation in soil water extraction between species on the shallow sandy loam soil at Merredin. However, C. arietinum, L. sativus and L. cicera had greater water extraction and P. sativum the least water extraction at Mullewa where soil conditions were less hostile and root penetration was not restricted. The pattern of water use varied markedly between the grain legume species examined. Grain yield was positively correlated with post-flowering water use ( Etpa) in both erect ( r=0.59) and prostrate ( r=0.54) grain legume species. Water use efficiencies for dry matter production ( WUEdm) of up to 30 kg ha −1 mm −1 for V. faba and V. narbonensis at Merredin, and water use efficiencies for grain yield ( WUEgr) of up to 16 kg ha −1 mm −1 for P. sativum and 13 kg ha −1 mm −1 for V. faba at Mullewa, were comparable to those reported for cereals and other grain legumes in previous studies in this and other environments. Potential transpiration efficiencies ( TE) of 15 kg ha −1 mm −1 together with soil evaporation ( Es) values of 100–125 mm were estimated in this and associated studies, and can be used as benchmark values to assess the yield potential of cool season grain legume crops in low rainfall Mediterranean-type environments. The major traits of adaptation for grain legume species producing large yields in this short season environment are early flowering, and pod and seed set before the onset of terminal drought. Early phenology together with rapid ground cover and dry matter production allows greater water use in the post flowering period. This leads to greater partitioning of dry matter into seed, which is reflected in greater harvest index (HI) and WUEgr, as was observed for V. faba and P. sativum. Improvement in the adaptation of other grain legume species to short season Mediterranean-type environments requires increased early growth for rapid ground cover and improved tolerance to low temperatures (especially for C. arietinum) during flowering and podding. 相似文献
12.
Low-input management for wheat production (less fungicide, low nitrogen rate) could affect grain protein content. The impact of the previous crop could also be a determining factor for wheat quality. A long-term field experiment located near Toulouse (southwestern France), comparing different rotations and management schemes from 1984 to 1993, was used to assess the effect of N availability and diseases on grain nitrogen concentration (GNC) of wheat. GNC ranged from 1.6 to 2.8%, increasing with the input level in 5 years out of 10, as the result of higher nitrogen levels and crop protection with fungicides. Leaf brown rust, high temperatures and water shortage, which affected dry matter accumulation during grain filling, were responsible for high GNC. GNC was generally correlated with N uptake when nitrogen availability was the main limiting factor and to the nitrogen harvest index (NHI) when foliar diseases or drought limited grain production. N uptake in the absence of N fertiliser ranged from 20 to 200 kg ha −1 depending on the previous crop. GNC was closely related to the nitrogen nutrition index (NNI) at anthesis. 相似文献
13.
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
14.
Published data on experiments with faba bean were used to develop a software tool for estimating the amount of nitrogen fixed (separately in grains and harvest residues) and the percentage of total nitrogen derived from the atmosphere (%Ndfa) from a minimum input data set of soil parameters (soil texture or, if available, soil yield potential, mineral nitrogen at the time of seeding, soil pH) and water supply during the period of growth. The tool is applicable for cropping situations in Central and Western Europe, where faba bean is grown as a spring crop. It is designed either for an assessment after the harvest of the crop (grain yield known) or for anticipating the nitrogen amounts resulting from cropping situations in the future (grain yield unknown). For the latter case a rough yield estimate is included. A comparison of estimated values of fixed nitrogen (t ha −1) and percentage of nitrogen derived from the atmosphere (%Ndfa) with data from the literature yielded coefficients of determination ( r2) of 0.53 for the amount of fixed nitrogen and 0.29–0.63, depending on the used dataset, for %Ndfa. 相似文献
15.
In rape ( Brassica napus L., cv. Global) seed growth mainly depends on husk CO 2 assimilation. In irrigated plants, the net photosynthetic rate ( Amax) was 10–13 μmol CO 2 m −2 s −1 in non-maturing pods and correlated with nitrogen content. The stomatal conductance of water vapour ( gH2O) was 0.3 mol m −2 s −1 in non-maturing pods. The photosynthetic nitrogen use efficiency (NUE) was 8.3 μmol CO 2g −1 N s −1, about one-third of that in leaves. The photosynthetic water use efficiency (WUE; AmaxgH2O−1) was similar in pods and leaves. In severely droughted plants, the photosynthetic rate was reduced to 38%. The seed growth rate, however, was not influenced by intermittent periods of water stress, indicating translocation of assimilates to the seeds. The drought resistant character of the pods was due to low specific area, succulence, low stomatal conductance causing a small decrease of ΔΨ day −1 during soil drying and maintenance of high relative water content during severe drought. A mathematical formulation of the pod water release curve was undertaken. © (1997) Elsevier Science B.V. 相似文献
16.
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
17.
From 1990 to 1993 nutrient fluxes were monitored on 38 private arable farms that had adopted farming strategies aiming at reduced nutrient inputs and substitution of mineral fertilizers by organic fertilizers. The nutrient surplus was defined as the difference between inputs (including inputs through deposition, seeds and biological fixation) and outputs in crop products, and amounted to 117 kg nitrogen (N), 14 kg phosphorus (P) and 21 kg potash (K) ha −1 year −1 on average. Potato and sugar beet had relatively high nutrient surpluses resulting both from crop characteristics and the use of organic manure. The surplus varied markedly among farms due to differences in cropping frequency, fertilizer inputs and crop outputs. Averaged over the years, ca. 70% of the participants achieved surpluses below 150 kg N, 20 kg P and 50 kg K ha −1 year −1. The amounts of residual soil mineral N (RSMN) exceeded those normally found in field experiments except for data collected after the wet summer of 1993. Distinct differences between crops were observed. Only in the case of potato a significant relationship was observed between the effective N input and RSMN. On a whole-farm level, RSMN amounted to more than 70 kg ha−1 N on 77, 74, 87 and 18% of the farms in the consecutive years. 相似文献
18.
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 NO 3−–N concentrations in soil. This caused an increase in grain yield in the three seasons. When the vinasse was applied with high doses, NO 3−–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
19.
Manganese deficiency symptoms are more often observed in crops at early stages of growth since Mn 2+ can be easily mobilized from the surface soil. The objectives of this study were to evaluate some of the popular rotation crops grown in Hungary for tolerance to low external Mn 2+ levels and to determine the critical tissue concentration for Mn 2+ deficiency during early stages of growth. Indicator plants of sunflower ( Helianthus annuus L.) were grown with NPKCaMg-fertilization induced of 0.0425–0.0700 g kg −1; of tobacco ( Nicotiana tabacum L.) 0.0237–0.0337 g kg −1; of triticale (x Triticosecale W.) 0.0103–0.0327 g NH 4-acetate + EDTA extractable soil Mn 2+ kg −1; and were grown for 73, 50, and 191 days. The minimum Mn 2+ concentration required in soil nutrient contents was 0.0425 g kg −1 for sunflower, 0.0243 g kg −1 for tobacco, and 0.0103 g kg −1 for triticale. Sunflower, tobacco and triticale achieved optimum growth from 0.048 to 0.065 g Mn 2+ kg −1, from 0.0249 to 0.0321 g Mn 2+ kg −1, and from 0.0287 to 0.0296 g Mn 2+ kg −1, respectively. Critical ABP's dry weight Mn 2+ concentration at early stages of growth was 0.0536 g kg −1 in sunflower, 0.458 g kg −1 in tobacco, and 0.1938 g kg −1 in triticale. Our results demonstrate that the tolerance to low external Mn 2+ (triticale <0.0302 g kg −1; sunflower <0.0562 g kg −1; tobacco <0.0693 g kg −1) and the critical tissue Mn 2+ levels for deficiency varied significantly among crop species tested. 相似文献
20.
In the Mediterranean zone, efforts to optimize combinations of supplemental irrigation (SI), improved varieties, nitrogen (N) and sowing dates aim to improve and stabilize cereal yields and maintain quality, especially for durum wheat. Thus, a 4 year field study (1992/1993 to 1995/1996) on a deep clay soil in northern Syria assessed the impact of SI (rain-fed, 1/3, 2/3 and full SI) combined with variable N application rates (0, 50, 100, 150 kg ha −1) and sowing date (early, normal, late) for four improved durum wheat varieties adapted to rain-fed and irrigated conditions. As rainfall and evapotranspiration varied over the 4 years, the amount of SI water required also varied. Yields varied with the season, and the main factors, except variety, were significant. Delaying sowing from November to January reduced yields and response to both SI and N. With irrigation, crop responses were generally significant up to 100 N ha −1, whereas the optimum response for rain-fed conditions occurred with 50 kg N ha −1. Limited SI (1/3) significantly increased yields, but almost maximum yields were obtained by 2/3 of full SI. Water- and N-use efficiencies were greatly increased by SI, with little variation among varieties. However, irrigation and delayed sowing decreased grain protein levels, which were partially compensated for by added N. A similar effect was observed for kernel vitreousness. Models developed from the response data can facilitate the potential transfer of these findings. Thus, in most growing seasons, minimum irrigation during the winter growing season, combined with appropriate fertilization, can enhance wheat output and yet maintain grain quality. 相似文献
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