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1.
The effect of slurry application techniques and slurry N stabilizing strategies on nitrous oxide emission from grasslands is poorly understood and, therefore, can result in large uncertainties in national/regional inventories. Field experiments were, thus, conducted to estimate the effect of different fertilization techniques on nitrous oxide (N2O) emissions. Fertilizer was applied (135–270 kg N ha−1 year−1) as calcium ammonium nitrate (CAN), untreated or treated cattle slurry. The slurry was either treated with sulfuric acid (target pH = 6.0), applied using trailing shoes or treated with 3,4-dimethyl pyrazole phosphate and applied via slot injection. N2O fluxes were sampled using the closed chamber technique. Cumulative N2O emissions ranged 0.1–2.9 kg N ha−1 year−1 across the treatment, sites and years. The N application techniques showed inconsistent effects on soil mineral N content, cumulative N2O emission and N yield. The fertilizer replacement value of slurry was low due to low N use efficiencies at the sites. However, a close positive relationship (r = 0.5; p = .013) between slurry value and biomass yield was observed, highlighting the benefit of high slurry value on crop productivity. N2O-N emission factors were low for all treatments, including CAN, but were 2–6 times higher in 2019 than in 2020 due to lower precipitation in 2020. Variations in N2O emission were largely explained by soil and climatic factors. Even with the low N2O emissions, this study highlights the benefit (significant mitigation of N2O emissions) of replacing the increasingly expensive chemical fertilizer N with input from slurry under favourable conditions for denitrification.  相似文献   

2.
Grassland renovation by cultivation and reseeding has been shown to increase short-term emissions of N2O, but there is uncertainty about long-term effects, despite the potential impacts of reseeding on sward composition and soil functions. A field experiment was therefore carried out to determine how N2O emissions from previously renovated grasslands varied in the intermediate to long-term, compared with an undisturbed permanent grassland (PG). Plots on the PG site were renovated, either two (G2) or five (G5) years prior to the two experimental years. In each sward age and experimental year, annual N2O-measurements were conducted on a weekly basis and compared with the undisturbed PG. Plots were either unfertilized or were fertilized with slurry (240 kg N ha−1 year−1). On average, annual N2O emissions were 0.39 kg N/ha for the unfertilized swards, and 0.91 kg N/ha for slurry-fertilized swards. Sward age had no effect on N2O emissions. With increasing sward age the proportion of legumes in the sward was reduced, but a minimum biological nitrogen fixation (BNF) of 88 kg N/ha was maintained even in the fertilized PG. Both sward age and BNF were of limited importance for the annual N2O emissions compared with the effects of soil carbon content and nitrogen surplus levels. However, measured N2O emissions were low in all sward age treatments, with a low risk of additional N2O emissions when BNF is taken into account in fertilizer planning.  相似文献   

3.
Water management is recognized as one of the most important factors in regulating nitrous oxide (N2O) emissions from paddy fields. In China, controlled irrigation (CI) is widely applied because it has been proved highly effective in saving water. During the rice-growing season, the soil in CI paddy fields remains dry 60–80% of the time compared with soil irrigated by traditional methods. This study aims to assess N2O emissions from paddy fields under CI, with traditional irrigation (TI) as the control. The cumulative N2O emission from CI paddy fields was 2.5 kg N ha−1, which was significantly greater than that from TI paddy fields (1.0 kg N ha−1) (P < 0.05). Soil drying caused substantial N2O emissions. The majority (73.9%) of the cumulative N2O emission from CI paddy fields was observed during the drying phase, whereas no substantial N2O emissions were observed when the soil was re-wetted after the drying phase. More and significantly higher peaks of N2O emissions from CI paddy fields (P < 0.05) were also detected. These peaks were observed ~8 days after fertilizer application at water-filled pore spaces (WFPS) ranging from 78.0 to 83.5%, soil temperature ranging from 29.1 to 29.4°C, and soil redox potential (Eh) values ranging from +207.5 to +256.7 mV. The highest N2O emission was measured 8 days after the application of base fertilizer at a WFPS of 79.0%, soil temperature of 29.1°C, and soil Eh value of +207.5 mV. These results suggest that N2O emissions may be reduced obviously by keeping the WFPS higher than 83.5% within 10 days after each fertilizer application, especially when the soil temperature is suitable.  相似文献   

4.
While the application rate of nitrogen fertilizer is believed to dramatically influence rice fields and improve the soil conditions in paddy fields, fertilization with low use efficiency and nitrogen loss may cause environmental pollution. In this paper, 15N-labeled urea was used to trace the fate of nitrogen at four rates (0, 75, 225 and 375 kg N/ha) of urea fertilizer over three split applications in Hangzhou, Zhejiang, in 2014. Plant biomass, the soil nitrogen content of different layers, NH3 volatilization and N2O emissions were determined using the 15N abundance to calculate the portion from nitrogen fertilizer. The results indicated that rice yields increased with the application rate of nitrogen fertilizer. NH3 volatilization is the main nitrogen loss pathway, and N2O emissions were significantly associated with nitrogen application rates in the paddy. The percent of nitrogen loss by NH3 volatilization and N2O emissions increased with the nitrogen application rate. This study showed that the suitable N fertilizer in a loam clay paddy, considering the yield requirements and environmental issues, is approximately 225 kg N/ha in Hangzhou, with a distribution of 50.06% of the residual in the rice and soil and 48.77% loss as NH3 volatilization and N2O emissions. The nitrate from fertilization mainly remained in the 0–20 cm level of the topsoil.  相似文献   

5.
In the low fertility acid soils of the Orinoquian savannas of Colombia, Urochloa humidicola cv. Tully or Humidicola is one of the most widely planted tropical forage grasses for improving livestock productivity. Low nutritional quality of this grass limits sustainable livestock production in this region. In this study, we conducted a phenotypic evaluation under field and greenhouse conditions of one of the first hybrid populations of U. humidicola generated from the forage breeding program of CIAT. Our objective was to identify a set of new hybrids of U. humidicola that combine improved productivity and nutritional quality plus the biological nitrification inhibition (BNI) trait/ability to reduce nitrogen (N) losses via leaching and nitrous oxide (N2O) emissions. To this end, we tested 118 hybrids (planted in pots) in the greenhouse for over 6 months and measured potential nitrification rates (NR) using soil microcosm incubation. NR values observed ranged from 0.27 to 5.75 mg N-NO3− kg soil−1 day−1. Later, 12 hybrids with different levels of NR were selected and field-tested in the Orinoquia region over a 4 years period (2013–2017) for dry matter production, nutrition quality (crude protein, in vitro digestibility and fibres content) and NR in each year. In the rainy season of 2018, two hybrids with superior agronomic performance and contrasting field level NR (Uh08/1149 and 0450) were subjected to analysis of soil-borne N2O emissions after fertilization during 13 days. The NR values recorded were not directly correlated with the forage quality parameters evaluated, however, the two grasses with the lowest NR values were among those with the highest biomass production, crude protein content, and N uptake. The grass hybrid Uh08/1149 and the germplasm accession CIAT 16888 were found as materials with superior forage value, with production of 14.1 and 14.6 tons dry matter ha−1 year−1 (up to 8% higher than the cv. Tully), crude protein of 11.5 and 9.1% per cut (up to 20% higher than the cv. Tully), and N uptake of 31.6 and 25.7 kg N ha−1 cut−1 (up to 30% higher than the cv. Tully). Additionally, these two grasses are likely to exhibit high-BNI ability, with potential to improve N use efficiency in managed pastures.  相似文献   

6.
Paddy fields are subjected to fluctuating water regimes as a result of the alternate drying and wetting water management, which often incurs a sensitive change in N2O emissions from paddy soils. However, how the soil moisture regulates the emission of N2O from paddy soil remains uncertain. In this study, three incubation experiments were designed to study the effects of constant and fluctuating soil moisture on N2O emission and the sources of N2O emission from paddy soil. Results showed that the N2O emission from paddy soil at 100 % WHC (water-holding capacity) was higher than that at 40, 65, 80, 120, and 160 % WHC, indicating that 100 % WHC was the optimum soil moisture content for N2O emission under the incubation experiment. Small peak of N2O flux appeared when the soil moisture content from 250 % WHC decreased near to 100 % WHC, lower than that triggered by nitrogen (N) fertilization, which was mainly owing to the low NH4 + concentration at this period. Nitrification dominated the emissions of N2O from paddy soil at 250 % WHC (54.96 %), higher than that of nitrification-coupled denitrification (6.74 %) and denitrification (38.3 %). The contribution of denitrification to N2O emissions (44.10 %) was equivalent to that of nitrification (44.45 %) in soil at 100 % WHC, which was higher than that of 250 % WHC treatment. In conclusion, the finding suggested that the peak of N2O in paddy soils during midseason aeration could be attributed to the occurrence of optimum soil moisture under sufficient N availability, favorable for the production and accumulation of N2O.  相似文献   

7.
Effect of biochar on CH4 and N2O emission from soils vegetated with paddy   总被引：1，自引：0，他引：1  
Biochar is believed to have positive impact on soil properties and plant yield. Due to the presence of C, it can also enhance CH4 emission in paddy soils. On the other hand, ammonium sulphate can decrease CH4 emission due to negative impacts on methanogenesis. Keeping these points in view, a pot experiment was conducted to determine the effect of biochar along with ammonium sulphate on CH4 and N2O emission from paddy soil. Analysis revealed that biochar treated soils released more CH4 compared to untreated. Ammonium sulphate treated soil emitted the highest N2O whereas biochar addition decreased its emission significantly. Further, total emission was found to be higher for CH4 (16.9–34.7 g/m2) in comparison to N2O (?0.05 to 0.02 g/m2) for all treatments. Biochar application has positive impact on plant variables such as panicle number and weight of panicles. This study suggests that biochar application significantly decrease N2O emission and increase CH4 emission possibly due to affecting the availability of organic C in the soil to microbial activity for methanogenesis. Another possibility for enhancing CH4 emission by following biochar could be attributed to the increase in plant biomass.  相似文献   

8.
Water management is known to be a key factor on methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) emissions from paddy soils. A field experiment was conducted to study the effect of continuous irrigation (CI) and intermittent irrigation (II) on these emissions. Methane, CO2, and N2O emissions from a paddy soil were sampled weekly using a semi-static closed chamber and quantified with the photoacoustic technique from May to November 2011 in Amposta (Ebro Delta, NE Spain). Intermittent irrigation of rice paddies significantly stimulated (N2O + N2)–N emission, whereas no substantial N2O emission was observed when the soil was re-wetted after the dry phase. The cumulative emission of (N2O + N2)–N was significantly larger from the II plots (0.73 kg N2O–N ha?1 season–1, P < 0.05) than from the CI plots (?1.40 kg N2O–N ha?1 season?1). Draining prior to harvesting increased N2O emissions. Draining and flooding cycles controlled CO2 emission. The cumulative CO2 emission from II was 8416.35 kg CO2 ha?1 season?1, significantly larger than that from CI (6045.26 kg CO2 ha?1 season?1, P < 0.05). Lower CH4 emission due to water drainage increased CO2 emissions. The soil acted as a sink of CH4 for both types of irrigation. Neither N2O–N nor CH4 emissions were affected by soil temperature. Global warming potential was the highest in II (4738.39 kg CO2 ha?1) and the lowest in CI (3463.41 kg CO2 ha?1). These findings suggest that CI can significantly mitigate the integrative greenhouse effect caused by CH4 and N2O from paddy fields while ensuring the highest rice yield.  相似文献   

9.
Multispecies swards, comprised of different plant functional groups have comparable production potential to high N input L. perenne swards at reduced N when legumes are included. However, information on the appropriate management of multispecies swards is limited. The effect of differing management practices on the herbage dry-matter (DM) production and botanical composition of different sward types was investigated using a 3 × 2 × 2 factorial design plot experiment. The experiment consisted of three sward types: L. perenne-only receiving (LP; 250 kg N ha−1 a−1); L. perenne-Trifolium repens (LP-TR); multispecies sward containing L. perenne, Phleum pratense, Trifolium repens, Trifolium pratense, Plantago lanceolata and Cichorium intybus (MSS). LP-TR and MSS received 90 kg N ha−1 a−1. Harvesting of plot herbage took place every 21 or 28 days to a defoliation height of 4 or 6 cm, over two growing seasons (March to November 2020 and 2021 inclusive). Annual herbage produced by both LP and LP-TR was not significantly affected by defoliation frequency. However, MSS produced 1923 kg DM ha−1 a−1 more herbage when harvested less frequently. Unsown species contributed significantly less to the herbage DM of MSS compared to LP and LP-TR and remained similar in 2020 and 2021, whereas the contribution of unsown species to herbage DM increased in LP and LP-TR from 2020 to 2021, with noxious species more associated with LP and LP-TR than MSS. Results demonstrate the role of multispecies swards in improving the sustainability of grass-based agricultural systems in an environment of reduced fertilizer inputs.  相似文献   

10.
Nitrogen fertilizer practices affect nitrous oxide (N2O) emissions from agricultural soils. The “4R” nutrient stewardship framework of using N fertilizer at the right rate, right source, right placement and right time can reduce N2O emissions while maintaining or improving yield of field crops, but understanding of how the various factors affect N2O emissions from irrigated processing potato is lacking. We examined the effects of selected 4R practices on emissions, using results from two irrigated processing potato studies each conducted in 2011 and 2012 in Manitoba, Canada. Experiment 1 examined combinations of source (urea, ESN), placement (pre-plant incorporation [PPI], banding), and rate (100 and 200 kg N ha-1) on a clay loam soil. Experiment 2 examined timing and source treatment combinations (urea PPI, ESN PPI, urea split, urea split/fertigation) on a loamy fine sandy soil. For Experiment 1, use of ESN at 200 kg ha-1 did not reduce area-, yield- and applied fertilizer N- based N2O emissions compared to urea at 200 kg ha-1, irrespective of placement. Emissions from pre-plant banding ESN at 200 kg ha?1, however, were 32% lower than from PPI ESN. For Experiment 2, compared to single pre-plant urea application, fertigation simulated by in-season application of urea ammonium nitrate (UAN) gave lower area-, yield- and applied fertilizer N- based emissions. Split urea ( \( \raisebox{1ex}{$2$}\!\left/ \!\raisebox{-1ex}{$3$}\right. \) pre-plant, \( \raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right. \) hilling) also reduced area- and yield- based N2O emissions compared to single pre-plant urea application. Emissions were generally lower at the site with loamy fine sandy soil than the site with clay loam soil. These results demonstrate that combinations of “4R” practices rather than source alone are best to achieve reductions in N2O emissions from irrigated potato production.  相似文献   

11.
Nitrous oxide (N2O) emission from croplands in China is a serious environmental concern. Water management is an important factor in regulating N2O emissions from croplands. In China, controlled irrigation (CI) is one mode of the water-saving irrigation for rice and is widely used. This study aims to assess the lasting effects of CI on N2O emissions from winter wheat croplands in Southeast China, with traditional irrigation (TI) as the control. CI performed during the rice-growing season had obvious lasting effects on N2O emissions of the subsequent winter wheat-growing season. Compared with TI, CI significantly increased the cumulative N2O emission by 129.1 % during the rice-growing season (p < 0.05), but significantly decreased it by 47.7 % during the wheat season (p < 0.05). Continuous flooding of the TI during most of the rice-growing season resulted in an increase in N2O emissions during the winter wheat-growing season. Over the whole annual cycle, the cumulative N2O emission from the plots under CI during the rice-growing season was 5.3 kg N2O–N ha?1, which was 103.2 % of that under TI (p > 0.05). The results suggest that CI does not significantly increase the cumulative N2O emission from the rice–winter wheat rotation systems while insuring rice and wheat yields. This study focuses on the lasting effects of water-saving irrigation mode during rice-growing season on N2O emissions during the following wheat-growing season. Thus, it is a development and complement of the previous researches on the effects of water-saving irrigation on N2O emissions from rice–winter wheat rotation croplands.  相似文献   

12.
Nitrous oxide (N2O) emission from flooded rice paddy fields was continuously measured by the closed chamber method at an experimental plot in Thailand for a whole cultivation period. To characterize the N2O emission with regard to the denitrification N loss, the C2H2 inhibition method was applied. Flood water on the soil greatly suppressed the N2O emission. The N2O emission was mitigated considerably by even a thin film of the flood water. The overall average N2O emissions under flood conditions for one crop season (83 days) at the control site and the C2H2 treated site were 10.3 and 11.8 μg N m−2 h−1, respectively. The N2O emission from the C2H2 treated site was consistently higher than that from the control site and the N2O emission from both sites followed the same diurnal and seasonal variation pattern, indicating the effect of denitrification inhibition by the supplied C2H2. The N2O emission enhanced along with temperature increase when NO3–N concentration in the soil water was above 0.4 mg N l−1 and soil temperature was above 24°C, suggesting specific temperature influence over the emission. The increase in NO3–N concentration and temperature in the soil affected only the N2O emission while the difference in the emission at the C2H2 treated site and the control site was not so much affected. It was suggested that most of the actively produced N2O under higher NO3–N concentration and temperature would likely to quickly emit to the atmosphere rather than to undergo further reduction to N2.  相似文献   

13.
Management decisions should facilitate the dominance of C3 perennial grasses over annuals. This study examined the effects of defoliation frequencies and nitrogen fertilization on the productivity and potential for persistence of Dactylis glomerata L. (DG cocksfoot, perennial) in multispecies swards. Treatments were randomly applied to 24 mini‐swards of DG + Bromus willdenowii Kunth (BW prairie grass, annual/biennial) in a factorial design of four defoliation frequencies, based on number of leaves per tiller, by two nitrogen winter fertilization levels (N? or N+). Regardless of fertilization, very frequent and repeated defoliations were related to decreases of about 43% of aboveground biomass and frequent defoliations with decreases of about 44% of vegetative tillers associated with horizontal space occupation and potential for persistence. Nevertheless, differences in DG aerial productivity or reserves were not detected between frequent and optimal defoliation frequencies. Combined effects of N+ and optimal frequency were related to root biomass increment of about 200%, compared with frequent defoliation, associated with competitiveness and survival of DG. Optimal defoliation frequency would have ecological but not production advantages, compared with frequent defoliations. The results are discussed in terms of more objective decision‐making in the management of multispecies swards.  相似文献   

14.
Intercropping has been a globally accepted practice for forage production, however, consideration of multiple performance criteria for intercropping including forage production, feed use efficiency and ruminal greenhouse gas emissions needs to be further investigated. A two-year field study was conducted to evaluate forage dry matter (DM) yield, nutritive value, feeding values and land-use efficiency as well as ruminal carbon dioxide (CO2) and methane (CH4) emissions of intercropped orchardgrass (Dactylis glomerata) and alfalfa (Medicago sativa) sown in five intercropping ratios (100:0, 75:25, 50:50, 25:75, and 0:100, based on seed weight) and three nitrogen (N) fertilizer levels (0, 50, and 100 kg ha−1). Increasing alfalfa proportion and N fertilizer level increased soil nutrients and the two-year total DM yield. Intercropping increased both land and nitrogen use efficiency (NUE) compared with monocultures. Greater NUE was obtained when N fertilizer was applied at 50 kg ha−1, compared with 100 kg ha−1. Increasing the proportion of alfalfa in intercrops increased the crude protein yield and rumen undegraded protein yield. Harvested forage intercrops were incubated with ruminal fluid for 48 h. Degraded DM yield, CO2 and CH4 emissions increased with increasing alfalfa proportion in intercrops. Overall, the 75:25 of orchardgrass-alfalfa intercrops was recommended as the best compromise between high forage productivity, superior feed use efficiency and low ruminal greenhouse gas emissions through complementary effects. The results indicate that the appropriate N fertilization level would be 50 kg ha−1 for acquiring higher nitrogen use efficiency and forage productivity.  相似文献   

15.
Burning of rice straw is a common practice in northwest India, where rice–wheat cropping system is extensively followed. The practice results in loss of nutrients, atmospheric pollution and emission of greenhouse gases. A field experiment was conducted at Indian Agricultural Research Institute, New Delhi, India during the rabi season (November to April) of 2002–2003 to evaluate the efficacy of the various modes of rice straw recycling in soil in improving yield and soil fertility and reducing not only carbon dioxide emission but also nitrous oxide (N2O) emission. The treatment with no rice straw incorporation and application of recommended doses of fertilizer (120, 26 and 50 kg N, P and K ha−1, respectively), gave the highest yield of wheat. Treatments with the incorporation of rice straw at 5 Mg ha−1 with additional amount of inorganic N (60 kg N ha−1) or inoculation of microbial culture had similar grain yields to that of the treatment with no straw incorporation. The lowest yield was recorded in the plots where rice straw was incorporated in soil without additional inorganic N and with manure application. All the treatments with rice straw incorporation had larger soil organic C despite the effect on the mineralisation of soil organic matter. Emission of N2O was more when additional N was added with rice straw and secondary when straw was added to the soil because of higher microbial activity. The study showed that burning of rice straw could be avoided without affecting yield of wheat crop by incorporating rice straw in soil with an additional dose of inorganic N or microbial inoculation. However, the reduction of N2O emission due to avoiding burning is in part counterbalanced by an increase in emission during the subsequent wheat cultivation.  相似文献   

16.
Effects of soil freezing on nitrogen (N) mineralization have been the subject of increased attention in the ecological literature, though fewer studies have examined N mineralization responses to successive mild freezing, severe freezing and cyclic freeze–thaw events. Even less is known about relationships of responses to soil N status. This study measured soil N mineralization and nitrification in the field along an experimental N gradient in a grassland of northern China during the dormant season (October 2005–April 2006), a period in which freezing naturally occurs. Net N mineralization exhibited great temporal variability, with nitrification being the predominant N transformation process. Soil microbial biomass C and N and extractable NH4 + pools declined by 40, 52, and 56%, respectively, in April 2006, compared with their initial concentrations in October 2005; soil NO3– pools increased by 84%. Temporal patterns of N mineralization were correlated with soil microbial biomass C and N. N mineralization and nitrification increased linearly with added N. Microbial biomass C in treated soils increased by 10% relative to controls, whereas microbial N declined by 9%. Results further suggest that freezing events greatly alter soil N dynamics in the dormant season at this site, with considerable available N accumulating during this period.  相似文献   

17.
Vietnam is one of the world’s top two rice exporting countries. However, rice cultivation is the primary source of agriculture’s greenhouse gas (GHG) emissions in Vietnam. In particular, strategies are required to reduce GHG emissions associated with the application of organic and inorganic fertilisers. The objective of this study was to assess the effects of various combinations of biochar (BIOC), compost (COMP) and slow-release urea (SRU) on methane (CH4) and nitrous oxide (N2O) emissions. In total, 1170 gas samples were collected from closed gas chambers in rice paddies at Thinh Long commune and Rang Dong farm in northern Vietnam between June and October 2014. The gas samples were analysed for CH4-C and N2O-N fluxes using gas chromatography. The application of BIOC alone resulted in the lowest CH4 emissions (4.8–59 mg C m?2 h?1) and lowest N2O emissions (0.15–0.26 µg N m?2 h?1). The combined application of nitrogen–phosphorus–potassium (NPK) + COMP emitted the highest CH4 (14–72 mg C m?2 h?1), while ½NPK + BIOC emitted the highest N2O (1.03 µg N m?2 h?1 in the TL commune), but it was the second lowest (0.495 µg N m?2 h?1) in the RD farm. Green urea and orange urea reduced N2O emissions significantly (p < 0.05) compared to white urea, but no significant differences were observed with respect to CH4 emissions. SRU fertilisers and BIOC alone measured the lowest greenhouse gas intensity, i.e. <2.5 and 3 kg CO2 eq. kg?1 rice grain, respectively. Based on these results, application of fertilisers in the form of BIOC and/or orange or green urea could be a viable option to reduce both CH4 and N2O emissions from rice paddy soils.  相似文献   

18.
In a small-plot trial five grass varieties bromegrass cv. Grasslands Matua, perennial ryegrass CVS. Melle (diploid) and Bastion, Condesa and Meltra (tetraploid) were established as grass/white clover swards with white clover cv. Menna. Productivity was measured under 6-weekIy cutting both without N fertilizer (No) and with 100 kg N ha?1 applied in spring (N100) Evaluation was made over 2 harvest years, 1986–87. Total mean annual production of herbage dry matter (DM) in the first harvest year at No and No was 5·07 t ha?1 and 6·93 t ha?1 respectively. In year 2, corresponding values were 11·81 and 12·67 t ha?1. In year 1, Matua swards at No and N100 yielded 5·08 and 6·65 t DM ha?1 compared with 507 and 70 t DM ha?1 for the mean of the four ryegrass varieties. In year 2, corresponding values were 12·90 and 12·29 for Matua and 11·54 and 12·78 for the four ryegrasses. In year 1, the digestable organic matter in the dry matter (DOMD) of the Matua swards was lower than that of Melle, Bastion and Condesa at NO, particularly at the first cut. In year 2, differences in DOMD between treatments and varieties were not significant. The proportion of white clover was found to be higher in the No than the N100 treatment, and also higher in year 2 in most treatments. For the No treatment Matua swards had the highest proportion of white clover in year 1 (32% compared with 24% for the mean of the ryegrass varieties) but the lowest proportion in year 2 (27% compared with 60% for the ryegrasses). For the No treatment in year 1 clover production was also 43% higher, on average, from the tetraploid treatments than with Melle as the companion grass; for this comparison in year 2 the differences were not significant. It is concluded that Matua bromegrass/white clover swards receiving no N fertilizer may have a good potential under cutting management. However, the evidence from this trial is that in the second year the proportion of white clover is lower with Matua swards than with perennial ryegrass as the companion grass.  相似文献   

19.
《Field Crops Research》2001,70(2):101-109
Field pea (Pisum sativum L.) and spring barley (Hordeum vulgare L.) were intercropped and sole cropped to compare the effects of crop diversity on productivity and use of N sources on a soil with a high weed pressure. 15N enrichment techniques were used to determine the pea–barley–weed-N dynamics. The pea–barley intercrop yielded 4.6 t grain ha−1, which was significantly greater than the yields of pea and barley in sole cropping. Calculation of land equivalent ratios showed that plant growth factors were used from 25 to 38% more efficiently by the intercrop than by the sole crops. Barley sole crops accumulated 65 kg soil N ha−1 in aboveground plant parts, which was similar to 73 kg soil N ha−1 in the pea–barley intercrop and significantly greater than 15 kg soil N ha−1 in the pea sole crop. The weeds accumulated 57 kg soil N ha−1 in aboveground plant parts during the growing season in the pea sole crops. Intercropped barley accumulated 71 kg N ha−1. Pea relied on N2 fixation with 90–95% of aboveground N accumulation derived from N2 fixation independent of cropping system. Pea grown in intercrop with barley instead of sole crop had greater competitive ability towards weeds and soil inorganic N was consequently used for barley grain production instead of weed biomass. There was no indication of a greater inorganic N content after pea compared to barley or pea–barley. However, 46 days after emergence there was about 30 kg N ha−1 inorganic N more under the pea sole crop than under the other two crops. Such greater inorganic N levels during early growth phases was assumed to induce aggressive weed populations and interspecific competition. Pea–barley intercropping seems to be a promising practice of protein production in cropping systems with high weed pressures and low levels of available N.  相似文献   

20.
Soil solarisation together with the application of animal manure has been described as an alternative process for control of Phytophthora capsici root rot in pepper crops. A mixture of fresh sheep manure and dry chicken litter (SCM) and a semi-composted mixture of horse manure and chicken litter (HCM) were applied at 5.1 kg m−2 (dry weight) under plastic sheets to reduce Phytophthora inoculum survival rate and disease incidence. Non-solarised (C) and solarised (S) soils were used as control treatments. Mean NH3 concentration increased in SCM during biodisinfestation process (14.8 mg NH3 m−3) compared with HCM (9.1 mg NH3 m−3), accounted for the higher organic N content and potential N mineralisation. The higher NH3 concentration in SCM could have contributed to reduce the inoculum survival rate (30.6% and 75.0% in SCM and HCM plots, respectively). Inoculum survival rate was not reduced in S (94.4%) as temperature was below 33 °C throughout the experimental period. After biodisinfestation treatment, N2O and CO2 emissions tended to be higher in SCM, despite high spatial variability. Cumulative N2O emissions were 1.31 and 0.42 g N2O-N m−2 in SCM and HCM after 43 days. The larger N application and organic N mineralisation rate on fresh manure amended soils might have contributed to higher N2O emissions during and after soil biodisinfestation by denitrification and nitrification, respectively. Cumulative CO2 emission averaged 211.0 and 159.9 g CO2-C m−2 in SCM and HCM, respectively. The soluble organic C, more abundant in fresh manure, might have favoured soil respiration in SCM. Disease incidence decreased in SCM and HCM plots (disease incidence, 2%-8%) in relation to solarised soils (42%) after 4 months. Microbial suppressiveness might have contributed to minimise Phytophthora disease incidence in SCM and HCM plots. Pepper fruit yield increased with manure amendment in SCM and HCM, which averaged 4.6 and 4.3 kg m−2, respectively. Further research will be necessary to guarantee an effective Phytophthora biodisinfestation by fitting manure N and organic matter applications, improving crop yield and reducing greenhouse gas pollution.  相似文献   

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