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1.
One experiment lasting for two years was carried out at Pegões (central Portugal) to estimate the impact of mature white lupine residue (Lupinus albus L.) on yield of fodder oat (Avena sativa L. cv. Sta. Eulalia) as the next crop in rotation, comparing with the continuous cultivation of cereal, under two tillage practices (conventional tillage and no-till) and fertilized with five mineral nitrogen (N) rates, with three replicates. Oat as a first crop in the rotation provided more N to the agro-ecosystem (63 kg N ha−1) than did lupine (30–59 kg N ha−1). This was at a cost of 100 kg of mineral N ha−1, whereas lupine was grown without addition of N. A positive response of oat as a second crop was obtained per kg of lupine-N added to the system when compared with the continuous oat–oat. The cereal also responded positively to mineral N in the legume amended soil in contrast with the oat–oat sequence where no response was observed, partly due to the fast mineralization rate of lupine residue and a greater soil N immobilization in the continuous oat system. Each kg N ha−1 added to the soil through the application of 73 kg DM ha−1 mature lupine residue (above- and belowground material) increased by 72 kg DM ha−1 the oat biomass produced as the second crop in rotation when 150 kg mineral N ha−1 were split in the season, independent of tillage practice. Mature legume residue conserved in the no-tilled soil depressed the yield of succeeding cereal but less than the continuous oat–oat for both tillage practices, where the application of mineral N did not improve the crop response.  相似文献   

2.
Two experiments were carried out at Pegões (central Portugal) to determine the potential N mineralization in a pulse amended disturbed and undisturbed soil incubated at several temperatures, and to evaluate for 2 years the yield and N2 fixation capacity of sweet lupine (Lupinus albus L. cv. Estoril) inoculated with a mixture of rhizobia strains or nodulated by indigenous soil bacteria and submitted to conventional tillage or no-till practices. A completely randomized block design for soil mobilization with three replicates was used for the laboratory study, and completely randomized blocks for inoculation and tillage treatments with four replicates were used for the lupine yield and N2 fixation experiment. Residue N immobilization occurred immediately after mature residue return to the soil independent of temperature, and was greater at 7 °C especially in the disturbed topsoil. Greater immobilization was also observed by doubling the amount of mature residue incorporated in the soil. This was expected since soil microorganisms would be in direct contact with the fresh organic matter and would be provided with more organic carbon under these circumstances. Nitrogen mineralization proceeded after 5 days of amendment. Potential N mineralization was higher at 25 °C than at 18 or 7 °C, for both conventional and no-till practices. At 25 °C, 42% of buried residue-15N was released over 210 days, at a smaller rate than 18 °C (49%) over 81 days. Lupine yield and N2 fixation capacity were similar in plots that were not inoculated and those receiving the mixture of three rhizobia strains. White lupine had an efficient symbiosis with indigenous soil rhizobia at pod-filling (>99%, >100 kg N ha−1 year−1) which was not affected by tillage. At this stage, plant residue including visible roots and nodules accounted for a soil N input of +96 kg ha−1 year−1 (91% of crop N), showing the large soil N benefit by the crop at this stage. The lupine residue at pod-filling stage can be used as a green manure under the conditions of organic farming systems. The apparent N “harvest” index of the pulse at pod-filling was only 9% though at maturity phase it should result in a higher value and the legume will show a lower fertilizer N value.  相似文献   

3.
The soil organic matter content represents a huge reservoir of plant nutrients and an effective safeguard against pollution; beside it can sequestrate atmospheric CO2. Since 1966 up to now in the Southeast Po valley (Italy), the soil organic C (SOC) and total N (TN) dynamics in the 0–0.40 m soil layer under a maize–wheat rainfed rotation are studied as influenced by organic and mineral N fertilizations. Every year in the same plots cattle manure, cattle slurry, and crop residues (i.e. wheat straw and maize stalk) are ploughed under to 0.40 m depth at a same dry matter rate (6.0 and 7.5 t DM ha−1 year−1 after wheat and maize, respectively) and are compared to an unamended control. Each plot is splitted to receive four rates of mineral fertilizer (0–100–200–300 kg N ha−1). In the whole experiment, in 2000 SOC concentration was lower than in 1966 (6.77 and 7.72 g kg−1, respectively), likely for the deeper tillage that diluted SOC and favoured mineralization in deeper soil layer. From 1972 to 2000 SOC stock did not change in the control and N fertilized plots, while it increased at mean rates of 0.16, 0.18, and 0.26 t ha−1 year−1 with the incorporation of residues, slurry and manure, corresponding to sequestration efficiencies of 3.7, 3.8 and 8.1% of added C with the various materials. TN followed the same SOC dynamic, demonstrating how it depends on the soil organic matter. Manure thus confirmed its efficacy in increasing both SOC content and soil fertility on the long-term. In developed countries, however, this material has become scarcely available; slurry management is expensive and implies high environmental risks. Moreover, in a C balance at a farm (or regional) scale, the CO2 lost during manure and slurry stocking should be considered. For these reasons, the incorporation of cereal residues, even if only a little of their C content was found capable of soil accumulation, appears the best way to obtain a significant CO2 sequestration in developed countries. Our long-term experiment clearly shows how difficult it is to modify SOC content. Moreover, because climate and soil type can greatly influence SOC dynamic, to increase CO2 sequestration in cropland, it is important to optimize the fertilization within an agricultural management that includes all the agronomic practices (e.g. tillage, water management, cover crops, etc.) favouring the organic matter build up in the soil.  相似文献   

4.
The European Water Framework Directive (2000) offers a new challenge for farmers and water policy makers. It requires the establishment of quantitative environmental diagnosis of water quality. This can be done using crop models properly tested in the short and long-terms and taking into account current farming practices. The aim of this paper is to check the robustness of a crop model (STICS) for predicting the nitrogen uptake and nitrate leaching in various fields during 8 successive years. The model was evaluated on the soil–crop database of a small catchment in northern France. It includes data of crop production and N uptake, water and mineral nitrogen contents in soil measured three times a year at 36 sampling sites representative of crops (wheat, sugar beet, pea, barley, oilseed rape) and soil parent materials (loam, loamy clay and rocks, sandy loam and limestone, sand). A few crop parameters of STICS were recalibrated on independent databases in order to improve the predictions obtained with the standard parameterization. STICS was then evaluated either by resetting simulations each year (RS) or during continuous simulations (CS) over the 8 years. A reasonable agreement was obtained between observed and simulated values, except for soil N mineral content at harvest and N content in crop residues. The model efficiencies using CS mode were 0.53, 0.94 and 0.38 for N uptake, soil water and mineral N in late autumn, respectively. The mean calculated drainage was 192 mm y−1 and N leaching was estimated at 20 kg N ha−1 y−1, respectively. Averaging the outputs according to soil and crop type improved the quality of fit. The outputs of CS simulations were close to those obtained with RS. The mean nitrate concentration in water drainage was estimated as 46 and 45 mg NO3 l−1 with RS and CS, respectively. Continuous simulations did not induce a substantial drift in mineral N in late autumn and can be trusted for predicting nitrate leaching. However, the leaching predictions were more sensitive to spatially variable parameters such as maximal rooting depth and potential mineralisation rate for CS than for RS. This emphasizes the difficulty in extrapolating the model over the long-term for large spatial areas. Another important uncertainty concerns fertiliser use efficiency, which had a small effect on leaching but a marked influence on gaseous N losses. Further assessments of the model will concern the whole N balance prediction over the long-term.  相似文献   

5.
Intensive cropping and exhaustive nature of sugarcane–wheat–rice cropping system in the Indo-Gangetic Plains of South Asia have led to the depletion of soil organic carbon content and inherent soil fertility resulting in a serious threat to the sustainability of these production systems. Bioagents like Gluconacetobacter diazotrophicus and Trichoderma viride have great potential to restore soil fertility and promote sugarcane growth. Field experiments, therefore, have been conducted to study the integrated effect of bioagents (G. diazotrophicus and T. viride), Farm Yard Manure (FYM) and fertilizer N on sugarcane rhizosphere, crop yield and N economy for two crop cycles during 2004–2006 and 2005–2007 crop seasons at Lucknow, in the middle Indo-Gangetic plain region. Both bioagents could survive and colonize sugarcane rhizosphere and FYM improved their colonization. Enhanced soil microbial population and microbial carbon (SMC) and nitrogen (SMN) with increasing N level were probably due to more available N in the soil. FYM/bioagents amendment further enhanced the microbial carbon. The uniform increase in the fraction of SMC and SMN of total organic carbon indicated that immobilization/mineralization was being maintained in the soil where enhanced microbial biomass might act later as a source of nutrients.Bioagents ammended FYM enhanced the uptake of N, P and K in sugarcane at all the levels of fertilizer N. It was mainly due to the enhanced nutrient availability in the rhizospheric soil as the soil organic C and available N, P and K content increased with the application of bioagents/FYM. A saving of 76.3 kg N ha−1 was envisaged by the use of G. diazotrophicus inoculated FYM with marginal (2.4 t ha−1) decline in the cane yield. Application of T. viride enriched FYM, however, brought economy in the use of fertilizer N by 45.2 kg ha−1 and also increased the yield by 6.1 t ha−1compared to the control treatment. Overall, strategic planning in terms of an integrated application of these bioagents/manures with fertilizer N will not only sustain soil fertility but will also benefit farmers in terms of reducing their dependence and expenditure on chemical fertilizers.  相似文献   

6.
Research on tomato tolerance to salt stress indicates that thresholds of ECe for the decrease of yield and plant growth are moderately high and differ among varieties. Some results suggest that nitrogen fertilisation may help increase the threshold for yield reduction. Most literature data have been collected either in small-scale containers or in the open field and both systems are often subjected to disturbances making hypotheses difficult to test. A set of experiments was conducted in large containers in a rainout-shelter field setting to assess the response of a “cherry”-type tomato variety to irrigation with saline water and to test the hypothesis that salt stress may be mitigated through nitrogen fertilisation.Tomato hybrid ‘TOMITO F 1’ was irrigated with water at four levels of salinity (0.7, 2.5, 5.0, and 10.0 dS m−1 ECw) and three levels of nitrogen fertilisation (no added nitrogen = N0, 120 kg ha−1 = N120, and 160 kg ha−1 = N160) in factorial combination. Plant growth and water use were measured throughout the growth cycle, and gas exchange and leaf water potentials were measured at the fruit-growing stage. Two growing cycles were completed, one with high initial soil nitrogen (HN) and the second with low initial soil nitrogen (LN).No interaction was found between the application of nitrogen and plant response to saline irrigation. Plant growth and yield were affected by the saline treatments and less by nitrogen fertilisation, especially in the HN treatment.Irrigations with saline water resulted in increased values of soil salinity. Water use was lower with increasing soil and water EC, and the marginal reduction ranged from about 31 mm for each dS m−1 of water EC at low salinity to about 6 mm for each dS m−1 at high water EC.The marginal reduction in yield ranged from about 3.3 t ha−1 for each dS m−1 at low salinity water to less than 0.6 t ha−1 for each dS m−1 at high EC of irrigation water. Yield reductions were mainly due to lower fruit weight. Biomass values decreased as the salinity levels increased and fruit quality was improved in both cycles with increasing salinity.The hypothesis that nitrogen fertilisation could help tomato plants increase tolerance to salinity was not confirmed by data of this experiment and alterations induced by salinity in plant growth, yield and quality stabilised at high levels of water EC.  相似文献   

7.
Crop residue is often grazed by sheep after harvest, over the dry summer period from December to March in Mediterranean environments. However, soil cover provided by crop residues is a key component of conservation agriculture for maintaining favourable soil structure and high yields.A series of 31 site × year experiments was conducted to assess the effect of summer stubble grazing on residue levels and following crop yields. Relatively light grazing, with stocking rates below 10 dry sheep equivalent (DSE) and between 90 and 471 DSE days ha−1, had no significant effect on the amount of residue, soil properties, soil water, weeds or yield in the following crop. The main effect of grazing was to knock down and scatter the standing crop residues. However, longer term grazing at relatively high intensity (956 DSE days ha−1) on heavy soil, over both summer and winter, as in a pasture phase, did significantly reduce residue levels, infiltration and yield (by 59%). The effect of summer grazing on soil mineral N was small and inconsistent, with increased mineral N, by about 3–7 kg N ha−1, following grazing at two of the 13 sites. By contrast, higher mineral N, by 2–15 kg N ha−1, was measured in the un-grazed plots at three of the 13 sites. This was due to increased growth of legume pastures in the absence of grazing.More research is needed to confirm the yield effects when cropping after an annual pasture/fallow that is grazed over summer and winter, particularly on different soil types.  相似文献   

8.
Sustainable agriculture requires assessments of nitrogen fluxes and monitoring of potential nitrate losses. Watershed studies are particularly valuable to calculate nitrogen balances and quantify the relative importance of different sources of inputs and outputs. A nitrogen balance was calculated from September 2004 to October 2006 in an agricultural watershed named Valle Volta (Northern Italy) located in a Nitrate Vulnerable Zone. The area, consisting of 17.4 km2 of arable land, with limited presence of urban areas and roads, is entirely below the sea level (3 m b.s.l. in average). Soils are typically Vertic Cambisols and Thionic Fulvisols with fine texture (silty clay or silty clay loam). About 45% of the agricultural soil is pipe-drained. The ground water level is maintained at 4.6 m b.s.l. by the activity of pumps that raise excess waters into a river. Water fluxes in and out from the basin were daily registered, and dissolved inorganic nitrogen concentration (N–NO3 + N–NH4) analyzed periodically. Data about fertilizers applications, seeds and crop yield were obtained from farmers’ interviews. Biological nitrogen fixation (BNF) was estimated on the base of dry matter yield. Major N inputs derived from fertilizers (174–188 Mg watershed−1 year−1), followed by BNF (126–131 Mg watershed−1 year−1). Maize was the crop receiving the highest fertilization rates, accounting for more than 40% of total fertilizer inputs. Saleable products were the main form of N leaving the watershed (317–338 Mg watershed−1 year−1). Nitrate was the main N form in irrigation and efflux water; its concentration was higher from autumn to spring, with peaks of 10–20 mg N L−1 in efflux water, while it was low in summer. Nitrogen losses with efflux water were higher in spring and in autumn. Overall, losses of nitrate by efflux water were limited if compared with literature data. Water balance in the area remained near zero at the beginning and the end of the first year, confirming the suitability of the area for this kind of study. The potential net contribution of each hectare of agricultural soil of Valle Volta basin to the N load toward the Adriatic sea is about 5.5 kg N. Our study demonstrated that in the Valle Volta watershed, total N outputs and inputs are of similar magnitude, indicating that crop management and especially N fertilization techniques has reached good levels of ecological sustainability.  相似文献   

9.
Phosphorus (P) deficiency has been shown to decrease accumulated intercepted solar radiation (RIcum) for sweet corn and in this paper the effects on radiation use efficiency (RUE) and leaf photosynthetic rate at 2000 μmol m−2 s−1 PPFD (P2000) are examined. Data from two consecutive field experiments on a low P site at Lincoln, New Zealand, were analyzed. In the first experiment (2001/2002) 0, 50, 100, 150 or 200 kg P ha−1 was applied to sweet corn followed by an additional 0, 0, 10, 20 or 40 kg P ha−1 in 2002/2003 applied to the same plots. Thus, total P applications were 0, 50, 110, 170, or 240 kg P ha−1.There were no differences in RUE between P treatments but RUE changed with crop ontogeny. The RUE was 0.66 g MJ−1 before each crop had 10 fully expanded leaves and RUE was 1.34 g MJ−1 after this. The cause of this difference between development stages was unclear, but it was not related to air temperature. In contrast to RUE, there were clear differences in P2000 due to differences in specific leaf phosphorus (SLP). At a SLP of 0.12 g P m−2 or greater, P2000 was a constant value of 34 μmol CO2 m−2 s−1. When SLP was less than 0.12 g P m−2 P2000 was reduced. The differences in P2000 between P treatments occurred when the plants were young (≤10 fully expanded leaves) and after this, SLP of all leaves exceeded 0.12 g P m−2 and there were no differences in P2000. These early leaves were unimportant in determining crop RUE but are likely to have been important in establishing the hierarchies that led to the changes in RIcum reported previously. These results demonstrate the importance of an adequate supply of P early in crop growth.  相似文献   

10.
Insufficient phosphorus (P) availability decreases the yield of Zea mays, particularly for sweet corn crops grown in cool environments. This research examined the mechanisms of yield reductions with initial emphasis on canopy expansion processes that affect the interception of solar radiation. Experiments in two consecutive seasons (2001/2002 and 2002/2003) were grown at a low P site (Olsen P = 6 μg ml−1) at Lincoln, New Zealand. Each experiment contained five rates of P application. In 2001/2002 rates of 0, 50, 100, 150, or 200 kg P ha−1 were applied. In 2002/2003 an additional 0, 0, 10, 20 or 40 kg P ha−1 was applied to the same plots producing total P treatments of 0, 50, 110, 170 or 240 kg P ha−1 summed over the two seasons.When P availability was limited (0 or 50 kg P ha−1) the rates of leaf tip and fully expanded leaf appearance were slower in both seasons. Phyllochrons (°Cd leaf tip−1) were 5 °Cd longer in crops that received 0 kg P ha−1 than those fertilised with ≥100 kg P ha−1. The area of individual leaves was also reduced by low P inputs but the ranking of leaf area by main stem leaf position was conservative. The leaf area of the largest leaf of the unfertilised crops was at least 22% less than the maximum measured leaf area in both seasons. In contrast, P fertiliser application had no effect on leaf senescence.The rate of leaf appearance per plant, individual leaf area and plant population were integrated to calculate green leaf area index (GLAI) and to estimate accumulated radiation interception (RIcum) for these crops. The total RIcum throughout the season in the unfertilised crops was 12–28% less than for those crops that received ≥100 kg P ha−1 in both seasons. This difference partly explained the differences in crop biomass production in response to P availability. A sensitivity analysis showed that RIcum was equally sensitive to changes of the rate of leaf appearance and the area of individual leaves in response to P supply. Both processes need to be incorporated in mechanistic models of P effects on Z. mays which can be used to design efficient P fertiliser strategies.  相似文献   

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