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1.
Information on the amount and spatial distribution of plant roots is increasingly needed for understanding and managing crop behaviour. Soil electrical resistivity (ρ) tomography has been proposed as a non-destructive method for root biomass quantification and mapping in trees but evidence is needed on the applicability of the technique at low root density and in herbaceous plants.We produced high-resolution 3D DC soil resistivity tomograms in containers with bare soil (B), and alfalfa (Medicago sativa L.) (A1) on a silt loam soil, and alfalfa on a loam (A2). Root biomass (RMD), root length density (RLD), soil electrical conductivity (EC) and water content (θ) were measured destructively.The pattern of soil resistivity matched the spatial distribution of θ in bare soil and of RMD in rooted soil. Univariate linear relations were found between ρ and θ in bare soil and between ρ, RLD and RMD in rooted soil. Across all data RMD and soil texture (P < 0.01) explained a high proportion of variability in soil resistivity.This allows to conclude that soil resistivity is quantitatively related to root biomass in herbaceous plants even at low root density (biomass < 0.001 Mg m−3), providing a basis for the development of resistivity-founded methods for the non-destructive spatial detection of root mass in situ, but the response in ρ is of the same order of magnitude as the effects of grain size and water content. Therefore in field studies reciprocal masking of low-density roots and other soil features is possible, and the effect of variation in other soil properties should be explicitly addressed.  相似文献   

2.
Different tillage systems (conventional, minimum, raised bed and no tillage) and four mulch levels (control, polythene, straw and soil) were compared in maize (Zea mays) and wheat (Triticum aestivum) production for three years on an experimental field (sandy loam) located at Dry Land Research Sub Station, Dhiansar, Jammu. Each treatment was replicated four times in split plot design. The aim of the research was to determine the influence of tillage and mulch practices on economics, energy requirement, soil physical properties and performance of maize and wheat. Tillage methods significantly affected the soil physical properties as change in soil moisture contents and infiltration rate of soil was recorded. The soil moisture contents in minimum tillage (MT) were maximum (12.4%, 16.6%) in surface soil as compared to conventional tillage (CT) in maize and wheat crops, respectively. Comparing to the CT infiltration rate was (1.16times, 1.21times and 1.11times) higher in minimum tillage (MT), no tillage (NT) and raised bed (RB), respectively in kharif season. Similar results were also found in rabi season. The greatest maize yield of 1865 kg ha?1 was achieved with CT system while not significantly lower yield was achieved with MT system (1837 kg ha?1). However, wheat yield was recorded higher in MT as compare to the CT system. Comparing to the energy requirement of different operations, MT required 34.3% less, NT 31.1% less and RB 46.0% less than the CT system. MT system saved 2.5 times energy in tillage operation compared to the CT system. The economic analysis also revealed that the maximum benefits could be obtained from MT (EUR 202.4 ha?1) followed by RB (EUR 164.2 ha?1) and NT (EUR 158.3 ha?1) and lowest in CT (EUR 149.5 ha?1). Benefit-cost ratio was highest in MT (0.71) and lowest in CT (0.44). Results revealed that mulch significantly affected the soil physical properties and growth of maize. The maximum soil moisture content, infiltration rate and grain yield of maize and wheat recorded higher in mulching practices over no mulch treatment. Polythene mulch and straw mulch were almost equally valuable in maize and wheat sequence. Tillage (minimum) and mulch (polythene and straw) have pronounced effect on soil physical properties (improved infiltration rate and conserve soil water), energy requirement, economics and growth of maize and wheat.  相似文献   

3.
Soil nitrogen (N) dynamics can be modified by cover crops in rotations with cereals. Although, roots are a major source of N, little is known about the dynamics of root decomposition of cash and cover crops. The objective of this study was to assess the effects that cover crop species have on i) the decomposition of spring wheat roots during the growth of cover crops, and ii) the decomposition of cover crop roots during the growing season of spring wheat. The experiment aimed also at comparing three non-winter hardy cover crops of varying shoot C/N ratios under low and high N input levels of 6 and 12 g N m−2 y−1, respectively. The experiment included spring wheat (Triticum aestivum L.) as the main crop and non-winter hardy cover crops (yellow mustard (Sinapis alba L.), phacelia (Phacelia tanacetifolia Benth), and sunflower (Helianthus annuus L.) as well as bare soil fallow treatment. Minirhizotrons were used to non-destructively assess the spatial and temporal patterns of root growth and decomposition from 0.10 to 1.00 m. Simultaneously, we grew all crops in soil columns to measure destructively C and N content in the roots. We concluded that wheat root decomposition was not affected by cover crop species. In contrast, during the growing season of wheat root decomposition of yellow mustard was on average twice as high for phacelia and sunflower as a consequence of a higher production of roots with a significantly higher C/N ratio compared to the other cover crops.  相似文献   

4.
The aims of these field experiments were to investigate the effectiveness of soil application of rubber tire ash in comparison with soil and foliar applications of zinc (Zn) sulfate to increase Zn and decrease cadmium (Cd) concentrations in wheat grain. A two-year field experiment was conducted during the 2007–2008 and 2007–2008 growing seasons at Isfahan research field, Iran. Ten different Zn-efficiency bread wheat cultivars (Triticum aestivum L.) commonly cultivated in different parts of Iran were subjected to no Zn fertilizer addition (control), soil application of 40 kg ha−1 ZnSO4, soil application of 100 (for the first year) and 250 (for the second year) kg ha−1 waste rubber tire ash, foliar application of Zn at the mid tillering stage, and foliar application of Zn at the early anthesis stage. In the foliar application, ZnSO4 was sprayed at a rate of 0.66 kg Zn/ha. Foliar spray of zinc sulfate at early anthesis, in general, had no significant effect on the yield and grain Cd while significantly increased grain Zn concentrations of most cultivars. On average, the foliar Zn treatment at the mid tillering stage (0.66 kg Zn/ha), decreased the mean grain Cd concentration from 0.032 mg kg−1 in the control treatment to 0.024 mg kg−1. While the grain Zn concentrations of some cultivars increased with soil application of Zn sulfate, they were not affected or even decreased in other cultivars. For most studied wheat cultivars, pre-planting application of rubber tire ash in soil resulted in a significant decrease of grain Cd concentrations. The results show that the effectiveness of soil and foliar application of Zn on yield and grain Zn and Cd concentrations greatly depends on the cultivar. The currently recommended rates of soil applications of Zn to ameliorate Zn deficiency are sufficient to increase grain Zn and decrease grain Cd concentrations in some wheat cultivars, while they do not in the others. In this study, soil application of 250 kg rubber tire ash/ha and foliar spray of 0.66 kg Zn/ha at tillering stage were the most effective treatments to ameliorate Zn deficiency and to increase Zn and decrease Cd concentration in grains of most wheat cultivars.  相似文献   

5.
APSIM Nwheat is a crop system simulation model, consisting of modules that incorporate aspects of soil water, nitrogen (N), crop residues, and crop growth and development. The model was applied to simulate above- and below-ground growth, grain yield, water and N uptake, and soil water and soil N of wheat crops in the Netherlands. Model outputs were compared with detailed measurements of field experiments from three locations with two different soil types. The experiments covered two seasons and a range of N-fertiliser applications. The overall APSIM Nwheat model simulations of soil mineral N, N uptake, shoot growth, phenology, kernels m−2, specific grain weight and grain N were acceptable. Grain yields (dry weight) and grain protein concentrations were well simulated with a root mean square deviation (RMSD) of 0.8 t ha−1 and 1.6 protein%, respectively. Additionally, the model simulations were compared with grain yields from a long-term winter wheat experiment with different N applications, two additional N experiments and regional grain yield records. The model reproduced the general effects of N treatments on yields. Simulations showed a good consistency with the higher yields of the long-term experiment, but overpredicted the lower yields. Simulations and earlier regional yields differed, but they showed uniformity for the last decade.In a simulation experiment, the APSIM Nwheat model was used with historical weather data to study the relationship between rate and timing of N fertiliser and grain yield, grain protein and soil residual N. A median grain yield of 4.5 t ha−1 was achieved without applying fertiliser, utilising mineral soil N from previous seasons, from mineralisation and N deposition. Application of N fertiliser in February to increase soil mineral N to 140 kg N ha−1 improved the median yield to 7.8 t ha−1 but had little effect on grain protein concentration with a range of 8–10%. Nitrogen applications at tillering and the beginning of stem elongation further increased grain yield and in particular grain protein, but did not affect soil residual N, except in a year with low rainfall during stem elongation. A late N application at flag leaf stage increased grain protein content by several per cent. This increase had only a small effect on grain yield and did not increase soil residual N with up to 40 kg N ha−1 applied, except when N uptake was limited by low rainfall in the period after the flag leaf stage. The economic and environmental optima in winter wheat were identified with up to 140 kg N ha−1 in February, 90 kg N ha−1 between tillering and beginning of stem elongation and 40 kg N ha−1 at flag leaf stage resulting in a median of 8.5 t ha−1 grain yield, 14.0% grain protein and 13 kg N ha−1 soil residual N after the harvest. The maximum simulated yield with maximum N input from two locations in the Netherlands was 9.9 t ha−1.  相似文献   

6.
Intercropping and drip irrigation with plastic mulch are two agricultural practices used worldwide. Coupling of these two practices may further increase crop yields and land and water use efficiencies when an optimal spatial distribution of soil water contents (SWC), soil temperatures, and plant roots is achieved. However, this coupling causes the distribution of SWCs, soil temperatures, and plant roots to be more complex than when only one of these agricultural practices are used. The objective of this study thus was to investigate the effects of different irrigation treatments on spatial distributions of SWCs, soil temperatures, and root growth in a drip-irrigated intercropping field with plastic mulch. Three field experiments with different irrigation treatments (high T1, moderate T2, and low T3) were conducted to evaluate the spatial distribution of SWCs, soil temperatures, and plant roots with respect to dripper lines and plant locations. There were significant differences (p < 0.05) in SWCs in the 0–40 cm soil layer for different irrigation treatments and between different locations. The maximum SWC was measured under the plant/mulch for the T1 treatment, while the minimum SWC was measured under the bare soil surface for the T3 treatment. This was mainly due to the location of drippers and mulch. However, no differences in SWCs were measured in the 60 100 cm soil layer. Significant differences in soil temperatures were measured in the 0 5 cm soil layer between different irrigation treatments and different locations. The soil temperature in the subsoil (15 25 cm) under mulch was higher than under the bare surface. The overlaps of two plant root systems in an intercropping field gradually increased and then decreased during the growing season. The roots in the 0 30 cm soil layer accounted for about 60% 70% of all roots. Higher irrigation rates produced higher root length and weight densities in the 0 30 cm soil layer and lower densities in the 30 100 cm soil layers. Spatial distributions of SWCs, soil temperatures, and plant roots in the intercropping field under drip irrigation were significantly influenced by irrigation treatments and plastic mulch. Collected experimental data may contribute to designing an optimal irrigation program for a drip-irrigated intercropping field with plastic mulch.  相似文献   

7.
Durum wheat (Triticum turgidum subsp. durum L.) is being increasingly grown in many areas of the world, but there is a lack of information about the physiological processes limiting grain yield. In this study, different rates of N and P fertilization were applied and the source:sink ratio was manipulated to examine the factor(s) limiting grain filling under rainfed conditions. Plants exposed to four fertilization treatments (control, 80 kg N ha?1 (N), 50 kg P ha?1 (P) and 80 kg N ha?1 and 50 kg P ha?1 (N–P)) and were artificially modified to obtain a range of different source:sink ratios. The treatments were (I) control; (II) half of the spike was removed; (III) all the spike was removed. The cultivar Cosmodur was used, which is widely grown in Greece and other Mediterranean countries and is quite productive especially under rainfed conditions. The distribution of dry matter, N and P among grains, stems and leaves was analyzed at anthesis and harvesting. Dry matter accumulation and partitioning into different plant parts was different between the fertilization treatments and the control. At anthesis, leaf + culm dry matter was higher than the chaff dry matter. Total aboveground biomass increased after anthesis in both years and at all fertilization treatments. N fertilization affected N concentration at the whole plant level at anthesis and at maturity. There was an average increase of 20% in N concentration with N application at anthesis in both years relative to the control. N content was affected by the fertilization treatments and it was increased by 33% over the 2 years of the study compared with the control. In addition, P fertilization affected P concentration both at anthesis and maturity in every plant organ, and there was also a significant effect of the change of P concentration at the two different growth stages. P accumulation was also affected by the fertilization regime and by the spike halving treatment. Dry matter translocation was an average of 22% higher at the fertilized treatments compared with the control, which indicates that fertilization led plants to translocate higher amount of dry matter. N and P translocation were affected by the fertilization treatment and in some treatments by the sink reduction. The spike reduction treatment increased the pre-anthesis contribution to seed indicating that the N and P remobilization from vegetative tissues were very important for grain development. The present study indicates that N and P fertilization and sink size can affect dry matter, N, and P accumulation, partitioning, and retranslocation of durum wheat which can affect seed yield.  相似文献   

8.
A better understanding of crop growth and nutrient uptake responses to the depth of fertilizer banded-placement in the soil is needed if growth and nutrient uptake responses are to be maximized. A two-year field study covering two rape seasons (2010–2011 and 2011–2012) was conducted to examine the effect of banded-placement of N–P–K fertilizer at various depths on growth, nutrient uptake and yield of oilseed rape (Brassica napus L.). The results showed that fertilization at 10 cm and 15 cm soil depth produced greater taproot length and dry weight than fertilization at 0 cm and 5 cm. 0 cm and 5 cm deep fertilization significantly increased the lateral root distribution at 0–5 cm soil depth, while 10 cm and 15 cm deep fertilization induced more lateral root proliferation at 5–15 cm soil depth. At 36 days after sowing (DAS), 5 cm deep fertilization produced better aboveground growth and nutrient uptake than 10 cm and 15 cm deep fertilization. However, reversed results were observed after 36 DAS. 10 cm and 15 cm deep fertilization produced more rapeseed than 0 cm and 5 cm deep fertilization, moreover, the yield difference was more significant in drought season (2010–2011) than in relatively normal season (2011–2012). In summary, these results preliminarily suggest that both 10 cm and 15 cm are relatively proper fertilizer placement depth when the practice of banding fertilizer is used in oilseed rape production. But from the viewpoint of diminishing the production cost, 10 cm deep fertilization should be recommended in actual farming. Because 15 cm deep fertilization may require higher mechanical power input, and thus resulting in higher cost of production.  相似文献   

9.
Ridge and furrow rainfall concentration (RC) system has gradually been popularized to increase water availability to crops for improving and stabilizing agricultural production in the semiarid area of northwest China. The system is comprised of two elements: the plastic-covered ridge serves as rainfall harvesting zones and the furrow serves as planting zones. To make this system more perfect for alleviating drought stress in semiarid region, it is necessary to test optimum planting systems. A field experiment was conducted from 2007 to 2010 to evaluate the effects of RC planting on soil moisture, wheat yield and water use efficiency (WUE) under different ridge widths. Four planting systems were designed (RC40: 40 cm ridge with 60 cm furrow width, RC60: 60 cm ridge with 60 cm furrow width, RC80: 80 cm ridge with 60 cm furrow width, and CF: conventional flat without ridging). The results showed that RC planting can significantly increase soil moisture in 0–200 cm during the growing seasons of winter wheat. The rainfall-harvesting effect increased with ridge width increasing. Winter wheat yield and WUE was significantly higher under RC60 than under CF by 405.1 kg ha−1 and 2.39 kg mm−1 ha−1, respectively, on average across the three experimental years (P < 0.05). The above findings indicate that RC60 can benefit winter wheat cropping for higher yield through improving soil moisture. It could be concluded that the RC planting system with 60 cm ridge and furrow width will offer a sound opportunity for sustainable farming in semiarid dryland agricultural area.  相似文献   

10.
Sequestration of C in arable soils has been considered as a potential mechanism to mitigate the elevated levels of atmospheric greenhouse gases. We evaluated impacts of conservation agriculture on change in total soil organic C (SOC) and relationship between C addition and storage in a sandy loam soil of the Indo-Gangetic Plains. Cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) crops were grown during the first three years (2008–2011) and in the last year, maize (Zea mays L.), wheat and green gram (Vigna radiate L.) were cultivated. Results indicate the plots under zero tillage with bed planting (ZT-B) and zero tillage with flat planting (ZT-F) had nearly 28 and 26% higher total SOC stock compared with conventional tillage and bed planting (CT-B) (∼5.5 Mg ha−1) in the 0–5 cm soil layer. Plots under ZT-B and ZT-F contained higher total SOC stocks in the 0–5 and 5–15 cm soil layers than CT-B plots. Although there were significant variations in total SOC stocks in the surface layers, SOC stocks were similar under all treatments in the 0–30 cm soil layer. Residue management had no impact on SOC stocks in all layers, despite plots under cotton/maize + wheat residue (C/M+ W RES) contained ∼13% higher total SOC concentration than no residue treated plots (N RES; ∼7.6 g kg−1) in the 0–5 cm layer. Hence, tillage and residue management interaction effects were not significant. Although CT-B and ZT-F had similar maize aboveground biomass yields, CT-F treated plots yielded 16% less maize biomass than CT-B plots. However, both wheat and green gram (2012) yields were not affected by tillage. Plots under C/M + W RES had ∼17, 13, 13 and 32% higher mean cotton, maize, wheat and green gram aboveground biomass yields than N RES plots, yielding ∼16% higher estimated root (and rhizodeposition) C input in the 0–30 cm soil layer than N RES plots. About 9.3% of the gross C input contributed towards the increase in SOC content under the residue treated plots. However, ∼7.6 and 10.2% of the gross C input contributed towards the increase in SOC content under CT and ZT, respectively. Thus, both ZT and partial or full residue retention is recommended for higher soil C retention and sustained crop productivity.  相似文献   

11.
Crop residue removal and subsoil compaction are limiting to yield improvement in the North China Plain (NCP). We conducted a field study composed of six consecutive crop growing seasons from 2010 to 2013 in Henan province, China, to determine responses of soil properties, crop root distribution and crop yield to tillage and residue management in a wheat–maize cropping system under irrigated conditions. Tillage practices comprised mouldboard ploughing (MP) to a depth of 15-cm, deep mouldboard ploughing (DMP) to a depth of 30-cm, and chisel ploughing (CP) to a depth of 30-cm. Crop residue management included crop residue retained (CRRet) and crop residue removed (CRRem). The results indicated that yields in DMP and CP increased by 6.0% and 7.3% for wheat and by 8.7% and 9.0% for maize, respectively, relative to MP. The CRRet treatment also increased wheat yield by 6.7% and maize yield by 5.0%. The yield increases under DMP and CP were related to reduced bulk density and soil penetration resistance, increased soil water content, improved total N distribution and improved root density (0–60-cm). Compared with MP, the root mass density under DMP and CP were increased by 43.4% and 42.0% for wheat and by 40.6% and 39.4% for maize, respectively. The yield increases under CRRet were also related to increased soil water content, reduced penetration resistance and increased N status (0–40-cm). Overall, for DMP + CRRet and CP + CRRet, a more favorable soil environment alongside greater root mass density and suitable spatial distribution resulted in higher grain yields of wheat and maize. Thus, compared with conventional shallow tillage practice, DMP or CP with residue application could improve soil quality and agricultural productivity under irrigated areas with loam soil in the NCP.  相似文献   

12.
Under irrigated Mediterranean conditions, no-tillage permanent bed planting (PB) is a promising agriculture system for improving soil protection and for soil carbon sequestration. However, soil compaction may increase with time up to levels that reduce crop yield. The aim of this study was to evaluate the mid-term effects of PB on soil compaction, root growth, crop yield and carbon sequestration compared with conventionally tilled bed planting (CB) and with a variant of PB that had partial subsoiling (DPB) in a Typic Xerofluvents soil (Soil Survey Staff, 2010) in southern Spain. Traffic was controlled during the whole study and beds, and furrows with (F + T) and without traffic (F − T), were spatially distinguished during measurements. Comparisons were made during a crop sequence of maize (Zea mays L.)—cotton (Gossypium hirsutum L.)—maize, corresponding to years 4–6 since trial establishment. After six years, soil compaction was higher in PB than in CB, particularly under the bed (44 and 27% higher in top 0.3- and 0.6-m soil layers, respectively). Around this time, maize root density at early grain filling was 17% lower in PB than in CB in the top 0.6-m layer. In DPB, the subsoiling operation was not effective in increasing root density. Nevertheless, root density appeared to maintain above-ground growth and yield in both PB and DPB compared to CB. Furthermore, at the end of the study, more soil organic carbon was stocked in PB than in CB and the difference increased significantly with a depth down to 0.5 m (5.7 Mg ha−1 increment for the top 0.5-m soil layer). Residues tended to accumulate on furrows, and this resulted in spatial and temporal differences in superficial soil organic carbon concentration (SOC) in the permanent planting systems. In PB, SOC in the top 0.05-m layer increased with time faster in furrows than on beds, and reached higher stable values (1.67 vs. 1.09% values, respectively). In CB, tillage homogenized the soil and reduced SOC in the top 0.05-m layer (average stable value of 0.96% on average for beds and furrows).  相似文献   

13.
The sustainability of growing a maize—winter wheat double crop rotation in the North China Plain (NCP) has been questioned due to its high nitrogen (N) fertiliser use and low N use efficiency. This paper presents field data and evaluation and application of the soil–vegetation–atmosphere transfer model Daisy for estimating crop production and nitrate leaching from silty loam fields in the NCP. The main objectives were to: i) calibrate and validate Daisy for the NCP pedo-climate and field management conditions, and ii) use the calibrated model and the field data in a multi-response analyses to optimise the N fertiliser rate for maize and winter wheat under different field managements including straw incorporation.The model sensitivity analysis indicated that a few measurable crop parameters impact the simulated yield, while most of the studied topsoil parameters affect the simulated nitrate leaching. The model evaluation was overall satisfactory, with root mean squared residuals (RMSR) for simulated aboveground biomass and nitrogen content at harvest, monthly evapotranspiration, annual drainage and nitrate leaching out of the root zone of, respectively, 0.9 Mg ha−1, 20 kg N ha−1, 30 mm, 10 mm and 10 kg N ha−1 for the calibration, and 1.2 Mg ha−1, 26 kg N ha−1, 38 mm, 14 mm and 17 kg N ha−1 for the validation. The values of mean absolute deviation, model efficiency and determination coefficient were also overall satisfactory, except for soil water dynamics, where the model was often found erratic. Re-validation run showed that the calibrated Daisy model was able to simulate long-term dynamics of crop grain yield and topsoil carbon content in a silty loam field in the NCP well, with respective RMSR of 1.7 and 1.6 Mg ha−1. The analyses of the model and the field results showed that quadratic, Mitscherlich and linear-plateau statistical models may estimate different economic optimal N rates, underlining the importance of model choice for response analyses to avoid excess use of N fertiliser. The analyses further showed that an annual fertiliser rate of about 300 kg N ha−1 (100 for maize and 200 for wheat) for the double crop rotation with straw incorporation is the most optimal in balancing crop production and nitrate leaching under the studied conditions, given the soil replenishment with N from straw mineralisation, atmospheric deposition and residual fertiliser.This work provides a sound reference for determining N fertiliser rates that are agro-environmentally optimal for similar and other cropping systems and regions in China and extends the application of the Daisy model to the analyses of complex agro-ecosystems and management practices under semi-arid climate.  相似文献   

14.
Different preceding crops interact with almost all husbandry and have a major effect on crop yields. In order to quantify the yield response of winter wheat, a field trial with different preceding crop combinations (oilseed rape (OSR)–OSR–OSR–wheat–wheat–wheat), two sowing dates (mid/end of September, mid/end of October) and 16 mineral nitrogen (N) treatments (80–320 kg N ha−1) during 1993/1994–1998/1999, was carried out at Hohenschulen Experimental Station near Kiel in NW Germany. Single plant biomass, tiller numbers m−2, biomass m−2, grain yield and yield components at harvest were investigated. During the growing season, the incidence of root rot (Gaeumannomyces graminis) was observed. Additionally, a bioassay with Lemna minor was used to identify the presence of allelochemicals in the soil after different preceding crops.Averaged over all years and all other treatments, wheat following OSR achieved nearly 9.5 t ha−1, whereas the second wheat crop following wheat yielded about 0.9 t ha−1 and the third wheat crop following 2 years of wheat about 1.9 t ha−1 less compared with wheat after OSR. A delay of the sowing date only marginally decreased grain yield by 0.2 t ha−1. Nitrogen fertilization increased grain yield after all preceding crop combinations, but at different levels. Wheat grown after OSR reached its maximum yield of 9.7 t ha−1 with 210 kg N ha−1. The third wheat crop required a N amount of 270 kg N ha−1 to achieve its yield maximum of 8.0 t ha−1.Yield losses were mainly caused by a lower ear density and a reduced thousand grain weight. About 4 weeks after plant establishment, single wheat plants following OSR accumulated more biomass compared to plants grown after wheat. Plants from the third wheat crop were smallest. This range of the preceding crop combinations was similar at all sampling dates throughout the growing season.Root rot occurred only at a low level and was excluded to cause the yield losses. The Lemna bioassay suggested the presence of allelochemicals, which might have been one reason for the poor single plant development in autumn.An increased N fertilization compensated for the lower number of ears m−2 and partly reduced the yield losses due to the unfavorable preceding crop combination. However, it was not possible to completely compensate for the detrimental influences of an unfavorable preceding crop on the grain yield of the subsequent wheat crop.  相似文献   

15.
Excessive application of N fertilizer in pursuit of higher yields is common due to poor soil fertility and low crop productivity. However, this practice causes serious soil depletion and N loss in the traditional wheat cropping system in the Loess Plateau of China. Growing summer legumes as the green manure (GM) crop is a viable solution because of its unique ability to fix atmospheric N2. Actually, little is known about the contribution of GM N to grain and N utilization in the subsequent crop. Therefore, we conducted a four-year field experiment with four winter wheat-based rotations (summer fallow-wheat, Huai bean–wheat, soybean–wheat, and mung bean–wheat) and four nitrogen fertilizer rates applied to wheat (0, 108, 135, and 162 kg N/ha) to investigate the fate of GM nitrogen via decomposition, utilization by wheat, and contribution to grain production and nitrogen economy through GM legumes. Here we showed that GM legumes accumulated 53–76 kg N/ha per year. After decomposing for approximately one year, more than 32 kg N/ha was released from GM legumes. The amount of nitrogen released via GM decomposition that was subsequently utilized by wheat was 7–27 kg N/ha. Incorporation of GM legumes effectively replaced 13–48% (average 31%) of the applied mineral nitrogen fertilizer. Additionally, the GM approach during the fallow period reduced the risk of nitrate-N leaching to depths of 0–100 cm and 100–200 cm by 4.8 and 19.6 kg N/ha, respectively. The soil nitrogen pool was effectively improved by incorporation of GM legumes at the times of wheat sowing. Cultivation of leguminous GM during summer is a better option than bare fallow to maintain the soil nitrogen pool, and decrease the rates required for N fertilization not only in the Loess Plateau of China but also in other similar dryland regions worldwide.  相似文献   

16.
A field experiment was carried out to assess the impact of elevated carbon dioxide (CO2) and temperature on phosphorous (P) nutrition in relation to organic acids exudation, soil microbial biomass P (MBP) and phosphatase activities in tropical flooded rice. Rice (cv. Naveen) was grown under chambered control (CC), elevated CO2 (EC, 550 μmol mol−1) and elevated CO2 + elevated temperature (ECT, 550 μmol mol−1 and 2 °C more than CC) in a tropical flooded soil under open top chambers (OTCs) along with unchambered control (UC) for three years. Root exudates were analyzed at different growth stages of rice followed by organic acids determination. Rhizospheric soil was used for analysis of soil phosphatase, MBP and available P. The total organic carbon (TOC) in root exudates was increased by 27.5% and 30.2% under EC and ECT, respectively over CC. Four different types of organic acids viz. acetic acid (AA), tartaric acid (TA), malic acid (MA) and citric acid (CA) were identified and quantified as dominant in root exudates, concentration of these was in the order of TA > MA > AA > CA. The TA, MA, AA and CA content were increased by 34.4, 31.1, 38.7 and 58.3% under ECT compared to that of UC over the period of 3 years. The P uptake in shoot, root and grain under elevated CO2 increased significantly by 29, 28 and 22%, respectively than CC. Soil MBP, acid and alkaline phosphatase activity was significantly higher under elevated CO2 by 35.1%, 27 and 36%, respectively, compared to the CC. Significant positive relationship exists among the organic acid exudation, MBP, phosphatase activities and P uptake by rice. The enhanced organic acid in root exudates coupled with higher soil phosphatase activities under elevated CO2 resulted in increased rate of soil P solubilization leading to higher plant P uptake.  相似文献   

17.
Soil management systems may negatively affect the quality of the soil. Policymakers and farmers need scientific information to make appropriate land management decisions. Conventional (CT) and zero tillage (ZT) are two common soil management systems. Comparative field studies under controlled conditions are required to determine the impact of these systems on soil quality and yields. The research presented studied plant and soil physical and chemical characteristics as affected by different agricultural management practices, i.e. ZT and CT, cropped with continuous wheat or maize in monoculture (M) or in a yearly rotation (R) of these two crops, either with residue retention (+r) or without residues retention (?r), in an experimental field in the Transvolcanic Belt of Mexico after 14 years. The dominant factors defining soil quality were organic C, total N, moisture, aggregate stability, mechanical resistance, pH and EC. The principal component combining the variables organic C, total N, aggregate stability and moisture content showed the highest correlations with final yield (R = 0.85 for wheat and 0.87 for maize).After 14 years of continuous practice, ZTM + r and ZTR + r had the best soil quality and produced the highest wheat and maize yields of average 2001–2004 (6683 and 7672 kg ha?1 and 5085 and 5667 kg ha?1, respectively). Removing the residues, i.e. treatments ZTM ? r with maize (average 2001–2004: 1388 kg ha?1) and ZTR ? r and CTR ? r with wheat (average 2001–2004: 3949 and 5121 kg ha?1), gave the lowest yields and less favourable soil physical and chemical characteristics compared to the other practices. It was found that zero tillage with residue retention is a feasible management technology for farmers producing maize and wheat in the agro-ecological zone studied, resulting in a better soil quality and higher yields than with the conventional farmer practice (maize monoculture, conventional tillage and residue removal).  相似文献   

18.
Cotton (Gossypium hirsutum L.) is the leading cash crop being grown across the globe including Pakistan. By the inclusion of insect resistant transgenic cotton (BT cotton), the cotton production has mounted many folds in Pakistan. BT cotton is mostly grown in Southern Punjab in cotton–wheat cropping system of Pakistan; however there exists a time conflict among wheat harvest and BT cotton sowing in this system. Wheat is harvested during late April but the ideal sowing time of BT cotton is early-mid March indicating a time conflict of 4–6 weeks which is becoming the main concern leading to wheat exclusion from this system. Intercropping of BT cotton in standing wheat is one of the possible options to manage this overlapping period. This two year field study was, therefore, conducted at two locations (Multan, Vehari) to evaluate the economic feasibility of relay intercropping of BT cotton through different sowing methods in BT cotton–wheat cropping system. BT cotton–wheat cropping systems included in the study were: conventionally tilled cotton (CTC) on fallow land during early and late March, CTC during late April after harvest of flat sown wheat (FSW), bed sown wheat (BSW) + intercropped cotton during early and late March, and ridge sown wheat (RSW) + intercropped cotton during early and late March. Planting cotton in fallow land with conventional tillage during early March had more seed cotton yield; whereas planting in the same way during April after wheat harvest had minimum seed cotton yield. Likewise, FSW had more yield than ridge and bed sown wheat with intercropped BT cotton during early or late March. However, the system productivity in terms of net income, benefit: cost ratio and marginal rate of return of BSW + intercropped BT cotton during early March was the highest during both years at both locations. However, the system with sole crop of BT cotton sown on fallow land during late or early March was the least economical even than the system with CTC during late April after harvest of FSW. In conclusion, BSW + intercropped cotton during early March may be opted to manage the time conflict and improve the economic productivity of BT cotton–wheat cropping system without wheat exclusion from the system.  相似文献   

19.
The lateness, tallness and high vigour of old tall durum wheat cultivars could be advantageous for dual-purpose use and their high propensity for lodging should be reduced by grazing. A 3-year field trial was performed in Sardinia, Italy, in a typical Mediterranean environment. Crops of the durum wheat cultivar Senatore Cappelli were sown in October, and grazing was simulated by clipping half of the plots at the terminal spikelet stage of development. The forage biomass derived from clipping varied greatly between seasons (from 0.8 to 3.3 t ha−1 dry matter) in response to the notable inter-seasonal variability in weather conditions. Cultivar Senatore Cappelli showed good recovery following clipping, with the ability to attain almost complete radiation interception well before anthesis. The high number of leaves that emerged after clipping might have contributed to this good recovery. Nevertheless, clipping reduced the dry matter produced by anthesis (16 t ha−1 in clipped compared to 21 t ha−1 in unclipped crops) as well as the final dry matter (DMMAT) (19 t ha−1 in clipped compared to 23 t ha−1 in unclipped crops), although these differences disappeared when the clipped biomass was included. The lower lodging observed at anthesis in the clipped (21%) compared with unclipped crops (63%) likely reduced the difference between treatments. The lower DMMAT of clipped treatments was reflected in a lower grain yield (GY) (3.4 t ha−1 vs 4.2 t ha−1 in the unclipped treatment). Clipping did not affect the amount of nitrogen present in the biomass, nitrogen uptake efficiency or radiation use efficiency. GY reduction after clipping was mediated by the reduction in spikes m−2 and kernels m−2 (KNO). Spike fertility was not affected by clipping, because the same amount of radiation was available for each spike (about 1 MJ). The period with reduced ground cover after clipping was reflected in an increased evaporation and reduced transpiration, which did not alter the total water used and increased the transpiration efficiency in terms of DMMAT.Old tall durum wheat cultivars manifested good suitability for dual-purpose use in environments with low attainable yields because their low grain yield potential contributed to reducing the negative effects of clipping on GY. Their high straw yield and kernel protein percentage represented an advantage with respect to semi-dwarf cultivars.  相似文献   

20.
Dryland wheat is the major contributor to wheat production in the world, where water deficiency and poor soil fertility are key factors limiting wheat grain yields and nutrient concentrations. A field experiment was carried out from June 2008 to June 2011 at Shilipu (latitude 35.12°N, longitude 107.45°E and altitude 1200 m above sea level) on the Loess Plateau (a typical dryland) in China, to investigate the effects of rotation with soybean (Glycine max) green manure (GM) on grain yield, total N and total Zn concentrations in subsequent wheat (Triticum aestivum L.), and on nitrate-N and available Zn in the soil. The benefits of crop rotation with soybean GM on wheat grain yields became more evident with time. In the second and third years, the grain yields of wheat rotated with soybean GM reached 4871 and 5089 kg ha−1 at the 108 kg N ha−1 rate. These yields were 21% and 12% higher than the highest yields of wheat under a fallow-winter wheat (FW) rotation. Rotation with soybean GM reduced the amount of N fertilizer required to obtain wheat grain yields and biomass levels similar to wheat grown in the FW rotation by 20–33%. In the first 2 years, average grain N concentrations over all N rates increased by 6% and 12%, and those of Zn increased by 26% and 14% under the soybean GM-winter wheat (SW) rotation, compared with the FW rotation. The increased grain N and Zn concentrations were found to be related to the increased concentrations of nitrate-N and available Zn in the soil, particularly at the sowing of winter wheat. However, grain N and Zn concentrations were not improved by rotation with soybean GM in the third year. This was attributed to the dilution effect caused by the more grain yield increase than its nutrient export. In conclusion, planting soybean for GM in fallow fields reduced the need for N fertilizer to enhance wheat yields in this dryland region. Change in wheat grain N and Zn concentrations was related to soil nutrient concentrations, and to the balance between increased grain yield and its nutrient export.  相似文献   

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