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1.
The sustainability of cropping systems can be increased by introducing a cover crop, provided that the cover crop does not reduce the cash crop yield through competition. The cover crop may be sown at the same time as a cash crop in the crop rotation. We carried out an experiment in 1999–2000 and 2000–2001 in the Paris Basin, to analyze the effects of simultaneously sowing winter wheat (Triticum aestivum L.) and red fescue (Festuca rubra L.), a turf grass. Competition between wheat and fescue was analyzed with one variety of red fescue, Sunset, and two varieties of wheat, Isengrain and Scipion, each sown at a density of 150 plants m?2. In this study, we evaluated the effect of undersown fescue on wheat yield and analyzed the competition between the two species in detail. The undersown red fescue decreased wheat yield by about 12% for Isengrain (8.7 t ha?1 for undersown Isengrain versus 9.8 t ha?1 for Isengrain alone) and 7% for Scipion (7.4 t ha?1 for undersown Scipion versus 8.0 t ha?1 for Scipion alone). During the early stages of wheat growth (up to the ‘1 cm ear’ stage, corresponding to stage 30 on Zadoks’ scale), undersown fescue and fescue sown alone grew similarly. However, fescue biomass levels were much lower (5.6 and 4.7 g m?2 for fescue grown alone and undersown fescue) than wheat biomass levels on the undersown plots (120 g m?2 for Isengrain and 111 g m?2 for Scipion). From the e1 stage onwards, the wheat canopy rapidly extended, whereas that of red fescue remained sparse. The time lag between the beginning of the rapid increase in LAI and PAR interception by wheat grown alone and that for fescue grown alone was 590 dd in the second year. This resulted in much slower growth rates for undersown fescue than for undersown wheat. Biomass production rate was therefore low for undersown fescue (12% those of fescue grown alone, on average, at the time of wheat harvest), as were levels of water and nitrogen use. Neither the water deficit that occurred during the second experiment nor the nitrogen nutrition status of the wheat on plots with undersown fescue significantly affected wheat biomass production after anthesis.The global interception efficiency index IG?i indicated that the fraction of the PARo intercepted by the wheat during its growth (255 days) was 0.35. 相似文献
2.
《Field Crops Research》2006,95(1):75-88
Long-term trends of crop yields have been used as a means to evaluate the sustainability of intensive agriculture. Previous studies have measured yield trends from long-term rice–rice and rice–wheat experiments in different sites from the slopes of individual site regressions of yield over time. The statistical significance of each site regression was determined but not that of the aggregate trend, which could give an indication of the magnitude and significance of global yield change.The random regression coefficient analysis (RRCA) and meta-analysis were used in this study to analyze the aggregate yield trend from several long-term experiments (LTE) across the Indo-Gangetic Plains (IGP) and outside the IGP. Both methods show that there has been a significant (p < 0.05) declining trend in rice yield in rice–wheat LTEs in South Asia including China with the recommended rates of nutrients, but that there has been no significant change in wheat and system (rice + wheat) yields. There was no significant year × region (IGP versus non-IGP) interaction in rice and wheat yields. However, RRCA showed that the average yield trend was significantly negative (−41.0 kg ha−1 yr−1) only in the IGP. In the rice–rice LTEs, there was a significant year × site (IRRI versus non-IRRI sites) interaction during the dry season but not the wet season. Rice yields declined throughout Asia in the wet season. The average system (dry + wet season rice) yield trends were significantly negative in both IRRI and non-IRRI sites (−170.1 and −52.8 kg ha−1 yr−1, respectively) but the magnitude of yield decline was significantly greater in the IRRI sites than in the non-IRRI sites.Rice in the rice–wheat LTEs showed a significantly positive yield trend with the addition of farmyard manure (FYM) but the initial yield was generally lower with FYM than without FYM. After 15 years, yield increase due to FYM was not evident in most of the LTE. 相似文献
3.
《Field Crops Research》2005,91(1):71-81
Wheat (Triticum aestivum L.) cultivation in no-till soil of a postrice harvest field utilizes residual soil moisture and reduces the time period from rice harvest to wheat seeding in intensive rice-wheat cropping systems. Some of the major constraints in no-till wheat production are high weed infestation, poor stand establishment due to rapid drying of topsoil and low nitrogen use efficiency (NUE). A field experiment was conducted at the research farm of the Wheat Research Centre, Dinajpur, Bangladesh, for two consecutive years to overcome those constraints, to evaluate rice straw as mulch, and to determine the optimum application rate of nitrogen (N) for no-till wheat. The treatments included 12 factorial combinations of three levels of mulching: no mulch (M0), surface application of rice straw mulch at 4.0 Mg ha−1 that was withdrawn at 20 days after sowing (M1), the same level of mulch as M1 but allowed to be retained on the soil surface (M2), and four nitrogen levels (control 80, 120 and 160 kg ha−1). Rice straw mulching had a significant effect on conserving initial soil moisture and reducing weed growth. Root length density and root weight density of wheat were positively influenced both by straw mulching and N levels. N uptake and apparent nitrogen recovery of applied N fertilizer were higher in mulch treatments M1 and M2 as compared to M0. Also mulch treatment of M1 and M2 were equally effective at conserving soil moisture, suppressing growth of weed flora, promoting root development and thereby improved grain yield of no-till wheat. N application of 120 kg ha−1 with straw mulch was found to be suitable for no-till wheat in experimental field condition. 相似文献
4.
《Field Crops Research》1999,61(1):23-35
Field experiments were conducted to investigate the performance of temperate legume species in rice-based cropping systems in a warm-temperate environment in Nepal. Over the period 1994–1996, various legume species were grown during the winter season (October–May) in the Kathmandu valley (27° N, 1350 m asl) with the aim of evaluating their biomass production and N fixation. A wide range of legume species including food, feed and green manure crops proved to be very well adapted to the winter growing conditions in this environment. The cultivation of temperate legume crops therefore, constitutes an alternative to traditional cropping practices such as growing wheat or leaving the land fallow. The temperate species appeared to capitalise on generally favourable growing conditions such as long growing season, low pest and disease pressure, high radiant energy receipt and cool night temperatures. However, performance varied greatly between species and years. Total dry matter yields ranged from 2 to 20 t ha−1 obtained with lentil (Lens culinaris Medic) and bitter lupin (Lupinus mutabilis), respectively. Highest seed yields were produced by fababean (Vicia faba) (5 t ha−1) and field pea (Pisum sativum var. arvense) (3 t ha−1) in the first season. Nitrogen yields and quantities of N fixed ranged from 18 to 481 kg ha−1 and from 0 to 463 kg ha−1, respectively. Large amounts of N were fixed by species such as fababean, Persian clover (Trifolium resupinatum) and bitter lupin. Early sowing in autumn was shown to be beneficial for some crops such as fababean, vetch (Vicia benghalensis) and Persian clover. In these cases, it is, therefore, important to reduce the turn-around interval after rice. Further research is required to fully determine the potential of temperate legume species in these environments with particular emphasis given to the identification of the most adapted cultivars and to reduce the need for irrigation of these winter crops. 相似文献
5.
《Industrial Crops and Products》2007,25(3):239-247
Rotation of winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) is the prevailing double-cropping system in the North China Plain. Typically, winter wheat is planted at the beginning of October and harvested during early June. Maize is planted immediately after wheat and harvested around 25th of September. The growing season of maize is limited to about 100–110 days. How to rectify the sowing date of winter wheat and the harvest time of summer maize are two factors to achieve higher grain yield of the two crops. Three-year field experiments were carried out to compare the grain yield, evapotranspiration (ET), water use efficiency (WUE) and economic return under six combinations of the harvest time of summer maize and sowing date of winter wheat from 2002 to 2005. Yield of winter wheat was similar for treatments of sowing before 10th of October. Afterwards, yield of winter wheat was significantly reduced (P < 0.05) by 0.5% each day delayed in sowing. The kernel weight of maize was significantly increased (P < 0.05) by about 0.6% each day delayed from harvest before 5th of October. After 10th of October, kernel weight of maize was not significantly increased with the delay in harvest because of the lower temperature. The kernel weight of maize with thermal time was in a quadratic relationship. Total seasonal ET of winter wheat was reduced by 2.5 mm/day delayed in sowing and ET of maize was averagely increased by 2.0 mm/day delayed in harvest. The net income, benefit–cost and net profit per millimetre of water used of harvest maize at the beginning of October and sowing winter wheat around 10th of October were greater compared with other treatments. Then the common practice of harvest maize and sowing winter wheat in the region could be delayed by 5 days correspondingly. 相似文献
6.
《Field Crops Research》2005,91(2-3):307-318
A 3-year field experiment examined the effects of non-flooded mulching cultivation and traditional flooding and four fertilizer N application rates (0, 75, 150 and 225 kg ha−1 for rice and 0, 60,120, and 180 kg N ha−1 for wheat) on grain yield, N uptake, residual soil Nmin and the net N balance in a rice–wheat rotation on Chengdu flood plain, southwest China. There were significant grain yield responses to N fertilizer. Nitrogen applications of >150 kg ha−1 for rice and >120 kg ha−1 for wheat gave no increase in crop yield but increased crop N uptake and N balance surplus in both water regimes. Average rice grain yield increased by 14% with plastic film mulching and decreased by 16% with wheat straw mulching at lower N inputs compared with traditional flooding. Rice grain yields under SM were comparable to those under PM and TF at higher N inputs. Plastic film mulching of preceding rice did not affect the yield of succeeding wheat but straw mulching had a residual effect on succeeding wheat. As a result, there was 17–18% higher wheat yield under N0 in SM than those in PM and TF. Combined rice and wheat grain yields under plastic mulching was similar to that of flooding and higher than that of straw mulching across N treatments. Soil mineral N (top 60 cm) after the rice harvest ranged from 50 to 65 kg ha−1 and was unaffected by non-flooded mulching cultivation and N rate. After the wheat harvest, soil Nmin ranged from 66 to 88 kg N ha−1 and increased with increasing fertilizer N rate. High N inputs led to a positive N balance (160–621 kg ha−1), but low N inputs resulted in a negative balance (−85 to −360 kg ha−1). Across N treatments, the net N balances of SM were highest among the three cultivations systems, resulting from additional applied wheat straw (79 kg ha−1) as mulching materials. There was not clear trend found in net N balance between PM and TF. Results from this study indicate non-flooded mulching cultivation may be utilized as an alternative option for saving water, using efficiently straw and maintaining or improving crop yield in rice–wheat rotation systems. There is the need to evaluate the long-term environmental risks of non-flooded mulching cultivation and improve system productivity (especially with straw mulching) by integrated resource management. 相似文献
7.
《Field Crops Research》2005,91(2-3):319-327
The consumer's interest in natural, unconventional and nutritional foods led to the development of new specialty foods based on grain blends. Components of such foods are often so-called ‘ancient wheats’ which were never the subject of modern plant breeding programmes. Khorasan or Oriental wheat (Triticum turanicum) is a neglected and underutilised tetraploid wheat species, which probably survived over the centuries in subsistence farming systems in the Near East and Central Asia. In the present study the agronomic potential of Khorasan wheat was evaluated under eastern Austrian conditions.Fourteen accessions of Khorasan wheat were investigated together with check durum wheat cultivars over a period of 4 years in the Marchfeld region, north-east of Vienna. The crops were sown both in autumn and spring.The investigated material was inferior to modern durum wheats in most agronomic traits. No accession was found to tolerate soil temperatures below −5 °C. Tolerance to drought and fungal diseases was limited and/or modest, and grain yields were significantly lower. While the best performing turanicum accessions yielded in average 385.8 and 233.8 g m−2 for autumn and spring sowing, respectively, the check winter durum yielded 466.5 g m−2 and the check spring durums between 351.5 and 391.8 g m−2. Several characteristic and interesting features were observed which permit successful marketing of pure Khorasan grain or as a component in grain blends, despite possible flour quality traits. The grain has an impressive kernel size and thousand kernel weight, in most cases greater than 50 g and often even greater than 60 g. The high thousand kernel weight might be a valuable trait to transfer into durum wheat to improve grain yield. Moreover, the grain has an amber colour and high vitreousness.Due to higher plant height, low lodging tolerance and high susceptibility against powdery mildew, Khorasan wheat is more suitable for organic farming systems. Although there is evidence that Khorasan wheat has low adaptation, it is of interest as an alternative cereal to increase diversity both in the field and on the consumer's table. However, further experiments are necessary: on the one hand to study the interactions between sowing rates, sowing dates, weed suppression, thousand kernel weight and kernel plumpness in order to find out optimal production procedures, and on the other hand to find out areas/fields with the best growth conditions for Khorasan wheat. 相似文献
8.
《Field Crops Research》2004,85(1):1-13
Reduced plant biomass and increased plant-to-plant variability are expected responses to crowding in monocultures, but the underlying processes that control the onset of interplant interference and the establishment of hierarchies among plants within a stand are poorly understood. We tested the hypothesis that early determined plant types (i.e. dominant and dominated individuals) are the cause of the large variability in final kernel number per plant (KNP) usually observed at low values of plant growth rate (PGR) around silking in maize (Zea mays L.). Two hybrids (DK696 and Exp980) of contrasting response to crowding were cropped at different stand densities (6, 9 and 12 plants m−2), row spacings (0.35 and 0.70 m), and water regimes (rainfed and irrigated) during 1999/2000 and 2001/2002 in Argentina. The onset of interplant competition started very early during the cycle, and significant differences (P<0.05) in estimated plant biomass between stand densities were detected as soon as V4–6 (DK696) and V6–7 (Exp980). Plant population and row spacing treatments did not modify the onset of the hierarchical growth among plants, but did affect (P<0.02–0.08) the dynamic of the process. For both hybrids, the rate of change in relative growth between plant types was larger at 9 and 12 plants m−2 (ca. 0.12 g/g per 100 °C day) than at 6 plants m−2 (ca. 0.07 g/g per 100 °C day). For all treatments, the largest difference in estimated shoot biomass between plant types took place between 350 (V7) and 750 °C day (V13) from sowing, and remained constant from V13 onwards. Dominant plants always had more kernels per plant (P<0.05) than the dominated ones, but differences between plant types in PGR around silking were significant (P<0.05) only at 12 plants m−2. Our research confirmed the significant (P<0.01) curvilinear response of KNP to PGR around silking, but also determined a differential response between plant types: the mean of residual values were significantly (P<0.01) larger for dominant than for dominated individuals. Estimated ear biomass at the onset of active kernel growth (R3) reflected the variation in KNP (r2≥0.62), and was significantly (P<0.01) related to estimated plant biomass at the start of active ear growth (ca. V13). This response suggested that the physiological state of each plant at the beginning of the critical period had conditioned its reproductive fate. This early effect of plant type on final KNP seemed to be exerted through current assimilate partitioning during the critical period. 相似文献
9.
《Field Crops Research》2001,69(3):259-266
Water-use efficiency (WUEDM) is directly related to radiation-use efficiency (RUE) and inversely related to crop conductance (gc). We propose that reduced WUEDM caused by shortage of nitrogen results from a reduction in RUE proportionally greater than the fall in conductance. This hypothesis was tested in irrigated wheat crops grown with contrasting nitrogen supply; treatments were 0, 80 and 120 kg N ha−1 in 1998 and 0, 80, 120 and 160 kg N ha−1 in 1999. We measured shoot dry matter, yield, intercepted solar radiation and soil water balance components. From these measurements, we derived actual evapotranspiration (ET), soil evaporation and transpiration, WUEDM (slope of the regression between dry matter and ET), WUEY (ratio between grain yield and ET), RUE (slope of the regression between dry matter and intercepted radiation), and gc (slope of the regression between transpiration and intercepted radiation). Yield increased from 2.3 in unfertilised to an average 4.7 t ha−1 in fertilised crops, seasonal ET from 311 to 387 mm, WUEDM from 23 to 37 kg ha−1 mm−1, WUEY from 7.6 to 12.4 kg ha−1 mm−1, RUE from 0.85 to 1.07 g MJ−1, while the fraction of ET accounted for soil evaporation decreased from 0.20 to 0.11. In agreement with our hypothesis, RUE accounted for 60% of the variation in WUEDM, whereas crop conductance was largely unaffected by nitrogen supply. A greater fraction of evapotranspiration lost as soil evaporation also contributed to the lower WUEDM of unfertilised crops. 相似文献
10.
《Field Crops Research》1999,63(1):79-86
This paper explores the possibility of improving yields of spring wheat (Triticum aestivum) by using plastic film mulching. Field experiments compared three mulching treatments viz. for 20 d (M1), 40 d (M2), and 60 d (M3) after sowing (DAS), with a non-mulch control (CK). Mulching increased temperature and moisture in the upper 5 cm of soil, and shoots emerged 8 d earlier than in CK. Mulching also increased number of tillers, length of the growing period, spikelet and grain numbers per spike, and the duration from flowering to harvest. In the mulched treatments, photosynthesis rate and soluble sugar content were higher in the vegetative period, but soluble sugar content was lower in the grain filling period relative to CK. Grain yield following 20 d mulching was greatest (8207 kg ha−1), and decreased gradually as the mulching period increased (7847 and 6702 kg ha−1 for M2 and M3, respectively). Plastic film removed after 20 d maximizes yield and minimizes soil pollution. 相似文献
11.
《Field Crops Research》2005,94(1):86-97
A 3-year field experiment in rainfed Vertisol was designed to study the effects of timing and splitting of N fertilizer on the efficiency of nitrogen in wheat (Triticum aestivum L.). A single rate of 150 kg N ha−1 was used, different fractions being applied at sowing, tillering and stem elongation. The experiment was designed as a randomized complete block with four blocks. At the same time, a 15N experiment was conducted within the main experiment area, with microplots, to quantify N uptake from fertilizer and soil. Mean wheat use of N fertilizer ranged from 14.1% when applied at sowing to 54.8% when applied as a top dressing at the beginning of stem elongation. The mean annual contribution of soil residual N and mineralization was 152 kg N ha−1, representing a considerable proportion of total wheat N uptake, ranging from 83.2% when N fertilizer was applied in the fall to 49.4% when it was applied at stem elongation. This would account for the poor and inconsistent response of grain yield and N efficiency indices, and for the importance of soil N in Vertisols for predicting wheat N fertilizer requirements, due to the carryover effect. Application of N fertilizer to wheat preferably as a top dressing, between tillering and stem elongation, is a strategy to be recommended from the standpoint both of the environment and of farmer returns. 相似文献
12.
《Field Crops Research》2004,85(2-3):213-236
Three different experiments were designed to study the effects of N fertilizer rate, timing and splitting, and the response to combined application of N and S fertilizer on the bread-making quality of hard red spring wheat (Triticum aestivum L.) over a 3-year period in Vertisols under rainfed Mediterranean conditions. The following parameters were analyzed: grain yield, test weight, grain protein content, gluten index and alveograph parameters (W: alveogram index; P: dough tenacity; L: dough extensibility; P/L: tenacity–extensibility ratio). The N rate experiment included rates of 0, 100, 150 and 200 kg N ha−1 applied on four different sites. The experiment was designed as a randomized complete block with four blocks. For the experiment on N timing and splitting, a single rate of 150 kg N ha−1 was used, different fractions being applied at sowing, tillering and stem elongation, at a single site; again, experimental design was a randomized complete block with four blocks. Finally, for the experiment on the response to combined application of N and S fertilizer, a single fertilizer dose of 150 kg N ha−1 was applied in two forms (urea+ammonium nitrate and urea+ammonium nitrosulfate) with one leaf application at ear emergence (zero, 25 kg S ha−1, 25 kg N ha−1, kg N ha−1 and 50 kg N ha−1), also at a single site, using a split-plot design with four replications. Year-on-year variation in rainfall led to marked variations in wheat yield, grain protein content and bread-making quality indices. A close correlation was observed between rainfall over the September–May period and both grain yield and grain protein content (optimum values for both being recorded in the rainfall range 500–550 mm) as well as the alveogram index. A negative correlation was observed between mean maximum temperatures in May and both test weight and alveogram index (W). N fertilizer rate had a more consistent effect on bread-making quality than on grain yield. The highest values for grain yield were recorded at an N rate of 100 kg ha−1, while maximum grain protein content values were recorded at 150 kg ha−1. Application of half or one-third of total fertilizer N at stem elongation improved grain yield and grain protein content with respect to applications at sowing alone or at both sowing and tillering. Increased N rates led to a considerable increase in W values and to a reduction in the P/L ratio, thus improving dough balance, with a negative effect on the gluten index. Leaf application of N at ear emergence only affected grain protein content and the W index. Soil or leaf application of S had no effect on protein quality indices. The response of grain yield and grain protein content to fertilizer N differed from that reported for temperate climates. 相似文献
13.
《Field Crops Research》2006,95(2-3):367-382
For maximizing water retention and attaining high yields, transplanting into puddled soil (TPR) is often considered the optimal method of rice (Orzya sativa L.) establishment. Alternative management techniques like direct seeding (DSR) and deep tillage have been proposed as mechanisms to improve soil physical properties for subsequent dry-season crops, but the risks to rice are uncertain. In this full factorial study on a valley terrace in Nepal, the influence of tillage (shallow—T1, deep chisel—T2, deep chisel + moldboard plough—T3) and establishment practice (TPR, DSR) on the field water balance and rice performance were evaluated in two adjacent landscape settings (terrace edge “upland”, central terrace “lowland”). Although deep tillage had only modest influences on seepage and percolation (SP) rates in both years (Y1, Y2), landscape placement and establishment practice had significant implications for the water balance (e.g. Y2 SP cm day−1: TPR-lowland = 1.6, DSR-lowland = 2.3, TPR-upland = 4.1, DSR-upland = 6.1). During low rainfall periods, however, soil water potential and drought vulnerability were governed solely by landscape placement. Despite water balance differences, there was little evidence that rice rooting behavior was substantially modified by landscape or establishment method. Weed biomass was higher in DSR, but was uncorrelated with water balance and productivity trends. In Y1, lower SP rates and more days with continuous flooding were positively associated with rice productivity. DSR yields were significantly lower than TPR in both landscape positions, with the lowland outperforming the upland (Y1 mt ha−1: TPR-lowland = 6.4, DSR-lowland = 5.2, TPR-upland = 5.7, DSR-upland = 4.7). To determine if N dynamics were contributing to productivity differences, fertilizer nitrogen was increased from 120 to 150 kg N ha−1 in Y2. Results suggest that DSR performance is comparable – and landscape less important – if nitrogen is non-limiting (Y2 mt ha−1: TPR-lowland = 6.9, DSR-lowland = 6.5, TPR-upland = 7.0, DSR-upland = 6.5); no aspect of the field water balance was associated with yield variability in Y2. For direct seeding in N-deficient farming systems, landscape criteria may prove useful for minimizing production risks by identifying field areas with lower SP rates. 相似文献
14.
《Journal of Cereal Science》2006,44(2):174-181
Fast protein liquid chromatography has been developed for purification of high-molecular-weight glutenin subunits HMW-GSs from wheat flour. Flour samples from four wheat cultivars with different HMW-GS alleles at Glu-A1, Glu-B1 and Glu-D1 loci were used to establish the method. The column material used was Resource™ Phe, and the optimal elution was with a gradient formed with buffer A [0.05 M Tris–HCl containing 4 M urea and 0.25 M (NH4)2SO4, pH 8.0] and buffer B [0.05 M Tris–HCl containing 4 M urea (pH 8.0)] at a flow rate of 0.5 ml/min. A pure single 1Dx-, 1Bx- HMW-GS, and all the y-type HMW-GSs present in one genotype can be reliably separated in a single step. 相似文献
15.
《Field Crops Research》2006,96(1):125-132
The late-season foliar application of urea may increase yield and grain quality of wheat (Triticum aestivum L.). Limited information is available regarding the effect of late urea spraying on the performance of wheat cultivars under various basal N fertilization rates. Field experiments were conducted during 2000 through 2002 to evaluate the responses of six winter wheat cultivars to foliar urea (30 kg N ha−1) treatment around flowering at low (67 kg N ha−1) and high (194 kg N ha−1) basal N fertilization rates. Following urea spraying at low N rate, all cultivars increased grain yields to a similar extent (by an average of 7.8% or 509 kg ha−1) primarily due to an increase in the 1000-kernel weight. No yield response to the late-season urea treatment occurred at high basal N rate where grain yields averaged 24.9% (1680 kg ha−1) higher than those at low N rate. In contrast, late foliar urea application similarly improved grain quality at both low and high N rates by an average of 5 g kg−1 (4.5%) for protein content, 3.2 cm3 (11.9%) for Zeleny sedimentation, and 20 g kg−1 (8.6%) for wet gluten. These quality increments were consistent in all growing seasons regardless of significant variations in grain yields and protein concentrations across years. However, most cultivars failed to achieve breadmaking standards at low N rate as quality increments associated with the urea treatment were relatively small when compared to those achieved by high basal N rate. Late urea spraying had no effect on the falling number, whereas some cultivars showed small, but significant reduction in the gluten index at both N rates. Cultivars improved the hectolitre weight with the late-season urea treatment only at low N rate. Significant cultivar × urea interactions existed for most quality traits, which were due to the cultivar differences in the magnitude of responses. Thus, late-season urea spraying consistently produced larger yields at low basal N rate, and resulted in cultivar-dependent increases in protein content, Zeleny sedimentation, and wet gluten at both low and high N rates. 相似文献
16.
《Field Crops Research》1998,59(2):91-98
Single irrigation, compared to the conventional four or five irrigations, has been practised in northern China on winter wheat on a relatively large scale since 1991. In a field study, irrigation was reduced from normally four times (I4, 4×75 mm) to one (I1, 75 mm at the end of the second internode elongation) in an area with an annual rainfall of about 600 mm. A control without irrigation (I0) was also included. Late sowing and early soil drying at seedling stage resulted in a relatively deep root system. Leaf area index, the size of upper leaves and the length of base internodes were also significantly reduced under I1, but kernel number per panicle was not reduced, suggesting that the development of inflorescence was not disrupted. During the active grain-filling stage, it was found that leaf water potential under I1 was maintained similar to that of I4, while daytime stomatal conductance was substantially reduced. Leaf temperature was increased, indicating an inhibited leaf transpiration. Early senescence was induced in I1 and I0 crops and resulted in a substantially lower kernel weight. Although the grain yield of I1 was reduced by about 15% from I4, the water-use efficiency (WUE) for total water consumption was increased by 24–30%. Single irrigation can potentially make wheat cropping sustainable in this area in terms of water usage and prevent further depletion of the underground water resource. Explanations for the small or zero reduction in yield are: (1) the encouraging development of a deep root system that enabled the plants to use more water at depth (below 1 m), which is recharged annually by the relatively high summer rainfall. (2) A large portion of root system in the drying soil and its induced shoot physiological changes, that is, reduced leaf expansion and stomatal conductance, which helped the plants to establish a better canopy structure with a much reduced water consumption. (3) An improved harvest index. 相似文献
17.
《Field Crops Research》1998,58(3):187-196
Shallow sowing and in ridges are common practices in the west-Asia north-Africa (WANA) region in rain-fed cereal farming. Soil water is often limited in the top soil layer at the optimum sowing time, and stands of wheat may be established poorly and have low yields unless sowing is delayed until later rainfall. Sowing more deeply may enhance establishment due to higher soil water content in the seed zone, leading to better germination and emergence of seedling. Otherwise, a grain yield reduction will occur due to the delay in sowing after the optimum time. In a 2-year field experiment at Tel Hadya, Syria, the optimum time of sowing for rainfed cereals was between early November and early December. The establishment of plants sown 3, 9, and 12 cm deep and in ridges was poorer than that of plants sown at 6 cm, causing reductions in tiller numbers, leaf area index (LAI) and yield. Grain yield from ridge planting was 40% lower on average than from sowing at 6 cm. At this depth, yields declined by 5% per week with delay in sowing after the optimum time at 6 cm depth, but by lesser amounts for other depths, and varied little for the ridge method of planting. To maximize yield in this environment, i.e., 2.5 t ha−1, it is important that crops are sown early at the appropriate depth, even when pre-sowing rainfall is less than enough to wet the profile fully. 相似文献
18.
《Field Crops Research》2006,98(1):52-59
This study explored whether the average grain weight of wheat tends to be reduced when grain number is increased due to either competition or, to a consistent increase in the relative proportion of grains of smaller weight potential. Three field experiments considering environmental, genetic and environmental × genetic effects on yield and its main components were analysed during the 2003/2004 growing season in two different locations within the Mediterranean area of Catalonia, Spain. The relationship between grain weight and number of grains per unit land area was analysed for both the average of all grains (AGW) and for grains in specific positions of the main-shoot spikes: proximal (CPg) and distal (CDg) grains of central spikelets, and proximal grains of the near apical (APg) and near basal (BPg) spikelets. The proportional contribution of grains per spike for the different grain positions and the relative contribution of spikes per m2 made by the main shoot or tillers were also examined.In the three experiments, AGW was reduced when grain number was increased due to genetic and/or environmental factors. However, the slopes of the straight-lines that represented the negative relationship between grain number and grain weight were lower (less negative) and less significant for CPg (b = −0.20, P > 0.20), CDg (b = 0.06, P > 0.20) and BPg (b = −0.21, P > 0.20) than for AGW (b = −0.40, P < 0.05). The proportional contribution of distal grains and tiller spikes (both with relatively light grains) were directly related to grain number increases. Therefore, as grain number increased there was a higher proportion of grains of low potential weight. Thus, the average grain weight was concomitantly reduced when grain number increased by increasing the proportion of “small grains” in the canopy independently of any competitive relationship between growing grains. 相似文献
19.
《Field Crops Research》2001,70(1):27-41
Many Australian cotton growers now include legumes in their cropping system. Three experiments were conducted between 1994 and 1997 to evaluate the rotational effects of winter or summer legume crops grown either for grain or green manuring on following cotton (Gossypium hirsutum L.). Non-legume rotation crops, wheat (Triticum aestivum) and cotton, were included for comparison. Net nitrogen (N) balances, which included estimates of N associated with the nodulated roots, were calculated for the legume phase of each cropping sequence. Faba bean (Vicia faba — winter) fixed 135–244 kg N ha−1 and soybean (Glycine max — summer) fixed 453–488 kg N ha−1 and contributed up to 155 and 280 kg fixed N ha−1, respectively, to the soil after seed harvest. Green-manured field pea (Pisum sativum — winter) and lablab (Lablab purpureus — summer) fixed 123–209 and 181–240 kg N ha−1, respectively, before the crops were slashed and incorporated into the topsoil.In a separate experiment, the loss of N from 15N-labelled legume residues during the fallow between legume cropping and cotton sowing (5–6 months following summer crops and 9 months after winter crops) was between 9 and 40% of 15N added; in comparison, the loss of 15N fertilizer (urea) applied to the non-legume plots averaged 85% of 15N added. Little legume-derived 15N was lost from the system during the growth of the subsequent cotton crop.The improved N fertility of the legume-based systems was demonstrated by enhanced N uptake and lint yield of cotton. The economic optimum N fertilizer application rate was determined from the fitted N response curve observed following the application of N fertilizer at rates between 0 and 200 kg N ha−1 (as anhydrous ammonia). Averaged over the three experiments, cotton following non-legume rotation crops required the application of 179 kg N ha−1, whilst following the grain- and green-manured legume systems required only 90 and 52 kg N ha−1, respectively.In addition to improvements in N availability, soil strength was generally lower following most legume crops than non-legume rotation crops. Penetrometer resistance during the growth of the subsequent cotton crop increased in the order faba bean, lablab, field pea, wheat, cotton, and soybean. It is speculated that reduced soil strength contributed to improvement in lint yields of the following cotton crops by facilitating the development of better root systems. 相似文献
20.
《Field Crops Research》2005,94(1):33-42
Subtropical highlands of the world have been densely populated and intensively cropped. Agricultural sustainability problems resulting from soil erosion and fertility decline have arisen throughout this agro-ecological zone. This article considers practices that would sustain higher and stable yields for wheat and maize in such region. A long-term field experiment under rainfed conditions was started at El Batán, Mexico (2240 m a.s.l.; 19.31°N, 98.50°W; fine, mixed, thermic, Cumulic Haplustoll) in 1991. It included treatments varying in: (1) rotation (continuous maize (Zea mays) or wheat (Triticum aestivum) and the rotation of both); (2) tillage (conventional, zero and permanent beds); (3) crop residue management (full, partial or no retention). Small-scale maize and wheat farmers may expect yield improvements through zero tillage, appropriate rotations and retention of sufficient residues (average maize and wheat yield of 5285 and 5591 kg ha−1), compared to the common practices of heavy tillage before seeding, monocropping and crop residue removal (average maize and wheat yield of 3570 and 4414 kg ha−1). Leaving residue on the field is critical for zero tillage practices. However, it can take some time—roughly 5 years—before the benefits are evident. After that, zero tillage with residue retention resulted in higher and more stable yields than alternative management. Conventional tillage with or without residue incorporation resulted in intermediate yields. Zero tillage without residue drastically reduced yields, except in the case of continuous wheat which, although not high yielding, still performed better than the other treatments with zero tillage and residue removal. Zero tillage treatments with partial residue removal gave yields equivalent to treatments with full residue retention (average maize and wheat yield of 5868 and 5250 kg ha−1). There may be scope to remove part of the residues for fodder and still retain adequate amounts to provide the necessary ground cover. This could make the adoption of zero tillage more acceptable for the small-scale, subsistence farmer whose livelihood strategies include livestock as a key component. Raised-bed cultivation systems allow both dramatic reductions in tillage and opportunities to retain crop residues on the soil surface. Permanent bed treatments combined with rotation and residue retention yielded the same as the zero tillage treatments, with the advantage that more varied weeding and fertilizer application practices are possible. It is important small-scale farmers have access to, and are trained in the use of these technologies. 相似文献