首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
The effects of an intercrop catch crop (Italian ryegrass) on (i) the amounts and concentrations of nitrate leached during the autumn and winter intercrop period, and (ii) the following crop, were examined in a lysimeter experiment and compared with that from a bare fallow treatment. The catch crop was grown in a winter wheat/maize rotation, after harvest of the wheat, and incorporated into the soil before sowing the maize. A calcium and potassium nitrate fertilizer labelled with 15N (200 kg N ha?1; 9.35 atom per cent excess) was applied to the winter wheat in spring. Total N uptake by the winter wheat was 154 kg ha?1 and the recovery of fertilizer-derived N (labelled with 15N) was 60%. The catch crop (grown without further addition of N) yielded 3.8t ha?1 herbage dry matter, containing 43 kg N ha?1, of which 4.1 % was derived from the 15N-labelled fertilizer. Two-hundred kg unlabelled N ha?1 was applied to the maize crop. During the intercrop period the nitrate concentration in water draining from the bare fallow lysimeters reached 68 mg N1?1, with an average of 40 mg N1?1. With the catch crop, it declined rapidly, from 41 mg N I?1 to 0.25 mg N I?1, at the end of ryegrass growth. Over this period, 110 kg N ha?1 was leached under bare fallow, compared with 40 kg N ha?1 under the catch crop. 15N-labelled nitrate was detected in the first drainage water collected in autumn, 5 months after the spring application. The quantity of fertilizer-N that was leached during this winter period was greater under bare fallow (18.7% of applied N) than when a catch crop was grown (7.1 %). In both treatments, labelled fertilizer-N contributed about 34% of the total N lost during this period. With the ryegrass catch crop incorporated at the time of seedbed preparation in spring, the subsequent maize grain-yield was lowered by an average of 13%. Total N-uptake by the maize sown following bare fallow was 224 kg N ha?1, compared with 180 kg ha?1 with prior incorporation of ryegrass; the corresponding values for uptake of residual labelled N were 3% (bare fallow) and 2% (ryegrass) of the initial application. Following the maize harvest, where ryegrass was incorporated, 22.7% of the previous year's labelled fertilizer addition was present in an organic form on the top 30 cm of lysimeter soil. This compares with 15.7% for the bare fallow intercropping treatment. Tracer analyses showed overall recoveries of labelled N of 91.7% for the winter wheat/ ryegrass/maize rotation and 97% for the winter wheat/bare fallow/maize rotation. The study clearly demonstrated the ecological importance of a catch crop in reducing N-leaching as well as its efficient use of fertilizer in the plant-soil system from this particular rotation. However, the fate of the organic N in the ploughed-down catch crop is uncertain and problems were encountered in establishing the next crop of maize.  相似文献   

2.
Nitrogen fixation in faba bean (Vicia faba cv. Mesay) as affected by sulfur (S) fertilization (30 kg S ha–1) and inoculation under the semi‐arid conditions of Ethiopia was studied using the 15N‐isotope dilution method. The effect of faba bean–fixed nitrogen (N) on yield of the subsequent wheat crop (Triticum aestivum L.) was also assessed. Sulfur fertilization and inoculation significantly (p < 0.05) affected nodulation at late flowering stage for both 2004 and 2005 cropping seasons. The nodule number and nodule fresh weighs were increased by 53% and 95%, relative to the control. Similarly, both treatments (S fertilization and inoculants) significantly improved biomass and grain yield of faba bean on average by 2.2 and 1.2 Mg ha–1. This corresponds to 37% and 50% increases, respectively, relative to the control. Total N and S uptake of grains was significantly higher by 59.6 and 3.3 kg ha–1, which are 76% and 66% increases, respectively. Sulfur and inoculation enhanced the percentage of N derived from the atmosphere in the whole plant of faba bean from 51% to 73%. This corresponds to N2 fixation varying from 49 to 147 kg N ha–1. The percentage of N derived from fertilizer (%Ndff) and soil (%Ndfs) of faba bean varied from 4.3% to 2.8 %, and from 45.1% to 24.0%, corresponding to the average values of 5.1 and 47.9 kg N ha–1. Similarly, the %Ndff and %Ndfs of the reference crop, barley, varied from 8.5 % to 10.8% and from 91.5% to 89.2%, with average N yields of 9.2 and 84.3 kg N ha–1. Soil N balance after faba bean ranged from 13 to 52 kg N ha–1. Beneficial effects of faba bean on yield of a wheat crop grown after faba bean were highly significant, increasing the average grain and N yields of this crop by 1.11 Mg ha–1 and 30 kg ha–1, relative to the yield of wheat grown after the reference crop, barley. Thus, it can be concluded that faba bean can be grown as an alternative crop to fallow, benefiting farmers economically and increasing the soil fertility.  相似文献   

3.
Abstract

Radioactive 137Cs concentrations of forage corn (Zea mays L.) and Italian ryegrass (Lolium multiflorum Lam.) in a double cropping system under continuous cattle farmyard manure (FYM) application were observed for more than 2 years after the Fukushima Daiichi Nuclear Power Station accident in 2011. The experiment field is located 110 km southwest of the Fukushima Daiichi Nuclear Power Station, and the soil contains 137Cs of 920 Bq kg?1 on average. For crop cultivation, nitrogen fertilizer was applied in addition to FYM. The 137Cs concentrations in corn decreased significantly between 2011 and 2012, but only differed significantly between 2012 and 2013 for the plot with no FYM application. For Italian ryegrass, no significant differences were observed between the harvest in 2012 and 2013 despite the FYM application rate. To minimize corn 137Cs concentrations, the FYM application rate should be more than and equal to 30 Mg ha?1 when FYM is used as the major nutrient source. Exchangeable potassium oxide (K2O) greater than around 0.3 g kg?1 was mostly maintained with the FYM application rates. Corn 137Cs concentration appeared to increase at exchangeable K2O levels below 0.15 g kg?1. These results suggest that continuous FYM application can maintain soil nutrients including K2O and thereby control radioactive Cs transfer from the soil. FYM application rate of 30 Mg ha?1 is within the levels recommended by the prefectural governments around Fukushima Prefecture for crop production before the accident. These levels are sufficient to decrease the radioactive Cs concentrations for corn. However, unlike corn, differences in soil chemical properties by FYM application did not affect 137Cs concentrations in Italian ryegrass in this study, although low exchangeable K2O seemed to increase concentrations of stable 133Cs. Further experiments should be conducted to understand the observed differences between corn and Italian ryegrass.  相似文献   

4.
 N2O emission rates from a sandy loam soil were measured in a field experiment with 2 years of perennial forage crops (ryegrass, ryegrass-red clover, red clover) and 1 year of spring barley cultivation. Spring barley was sown after the incorporation of the forage crop residues. All spring barley plots received 40 kg N ha–1 N fertiliser. Ryegrass, ryegrass-red clover and red clover plots were fertilised with 350 kg N ha–1, 175 kg N ha–1 and 0 kg N ha–1, respectively. From June 1994 to February 1997, N2O fluxes were continuously estimated using very large, closed soil cover boxes (5.76 m2). In order to compare the growing crops, the 33 months of investigation were separated into three vegetation periods (March–September) and three winter periods (October–February). All agronomic treatments (fertilisation, harvest and tillage) were carried out during the vegetation period. Large temporal changes were found in the N2O emission rates. The data were approximately log-normally distributed. Forty-seven percent of the annual N2O losses were observed to occur during winter, and mainly resulted from N2O production during daily thawing and freezing cycles. No relationship was found between the N2O emissions during the winter and the vegetation period. During the vegetation period, N2O losses and yields were significantly different between the three forage crops. The unfertilised clover plot produced the highest yields and the lowest N2O losses on this soil compared to the highly fertilised ryegrass plot. Total N2O losses from soil under spring barley were higher than those from soil under the forage crops; this was mainly a consequence of N2O emissions after the incorporation of the forage crop residues. Received: 31 October 1997  相似文献   

5.
Catch crop strategy and nitrate leaching following grazed grass-clover   总被引：1，自引：0，他引：1  
Cultivation of grassland presents a high risk of nitrate leaching. This study aimed to determine if leaching could be reduced by growing spring barley (Hordeum vulgare L.) as a green crop for silage with undersown Italian ryegrass (Lolium multiflorum Lam.) compared with barley grown to maturity with or without an undersown conventional catch crop of perennial ryegrass (Lolium perenne L.). All treatments received 0, 60 or 120 kg of ammonium‐N ha?1 in cattle slurry. In spring 2003, two grass‐clover fields (3 and 5 years old, respectively, with different management histories) were ploughed. The effects of the treatments on yield and nitrate leaching were determined in the first year, while the residual effects of the treatments were determined in the second year in a crop of spring barley/perennial ryegrass. Nitrate leaching was estimated in selected treatments using soil water samples from ceramic cups. The experiment showed that compared with treatments without catch crop, green barley/Italian ryegrass reduced leaching by 163–320 kg N ha?1, corresponding to 95–99%, and the perennial ryegrass reduced leaching to between 34 and 86 kg N ha?1, corresponding to a reduction of 80 and 66%. Also, in the second growing season, leaching following catch crops was reduced compared with the bare soil treatment. It was concluded that the green barley/Italian ryegrass offers advantages not only for the environment but also for farmers, for whom it provides a fodder high in roughage and avoids the difficulties with clover fatigue increasingly experienced by Danish farmers.  相似文献   

6.
Abstract. After six years of bush‐fallow, residual effects on soil productivity of tillage practices prior to the fallow were investigated on an Alfisol in south western Nigeria. In 1996 fallow was followed by maize intercropped with cover crops of Pueraria phaseoloides, Mucuna pruriens or cowpea (Vigna unguiculata) and no intercrop. Parameters measured included soil properties, ground cover, crop growth and yield, rainfall erosivity, runoff and soil loss. In spite of six‐years of bush‐fallow and establishment of cover crops, soil erosion was significantly greater on plots that had been conventionally cultivated previously using disc ploughs, harrows and mechanical rotovators (1.78 t ha?1season?1) compared to previously no‐till plots (1.34 t ha?1season?1). Crop growth and yields were least and soil loss greatest (2.83 t ha?1season?1) on the previous bare plot. Maize grain yield was highest using Pueraria phaseoloides as an intercrop (2.15 t ha?1) followed by a cowpea intercrop (1.92 t ha?1), maize without intercrop (1.87 t ha?1) and Mucuna pruriens intercrop (1.71 t ha?1). The maize grain yields reflected levels of competition from the cover crops. Cowpea–maize intercrop may be most suitable for farmers because maize yields were satisfactory and cowpea grain serves as additional subsistence. Cowpea yields were 390 kg ha?1. Soil erosion was also moderate using cowpea as an intercrop (1.71 t ha?1season?1). However, Pueraria phaseoloides gave the best erosion control with a soil loss of 1.34 t ha?1season?1.  相似文献   

7.
Fertilizer phosphorus (P) is generally added to agricultural soils to meet the needs of crop production. In this study, the crop yield and soil Olsen P were measured every year (5–18 years) at 16 winter wheat (Triticum aestivum L.) –maize (Zea mays L.) crop rotation sites in cinnamon soil (Luvisols in FAO system). The mean agronomic critical value of Olsen P for maize was 14.2 mg kg?1 and for winter wheat was 14.4 mg kg?1 when using the Liner-plateau and Mitscherlich models. The change in soil Olsen P was positively linearly correlated with the P budget (P < 0.01), and an increase of 4.70 mg kg?1 in soil Olsen P for each 100 kg ha?1 of P budget in the 0–20 cm soil layer. A model of P fertilizer recommendation rate that integrated values of the change in soil Olsen P in response to P budget and the agronomic critical value of Olsen P was used, in order to adjust current levels of soil Olsen P to the agronomic critical value at the experimental sites over the next 5 years, P fertilizer application rate should be in the range of 0–87.5 kg P ha?1.  相似文献   

8.
Abstract. Three successive crops of winter wheat were grown on a sandy loam to test the residual effect of long‐term annual incorporation of spring barley straw at rates of 0, 4, 8 and 12 t ha?1, and ryegrass catch crops with or without additions of pig slurry. Soil receiving 4, 8 and 12 t ha?1 of straw annually for 18 years contained 12, 21 and 30% more carbon (C), respectively, than soil with straw removal, and soil C and nitrogen (N) contents increased linearly with straw rate. The soil retained 14% of the straw C and 37% of the straw N. Ryegrass catch‐cropping for 10 years also increased soil C and N concentrations, whereas the effect of pig slurry was insignificant. Grain yield in the first wheat crop showed an average dry matter (DM) increase of 0.7 t ha?1 after treatment with 8 and 12 t straw ha?1. In the two subsequent wheat crops, grain yield increased by 0.2–0.3 t DM ha?1 after 8 and 12 t straw ha?1. No grain yield increases were found after 4 t straw ha?1 in any of the three years. Previous ryegrass catch crops increased yields of wheat grain, but effects in the third wheat crop were significant only where ryegrass had been combined with pig slurry. Straw incorporation increased the N offtake in the first wheat crop. In the second crop, only 8 and 12 t straw ha?1 improved wheat N offtake, while the N offtake in the third wheat crop was unaffected. Ryegrass catch crops increased N offtake in the first and second wheat crop. Again, a positive effect in the third crop was seen only when ryegrass was combined with slurry. Long‐term, annual incorporation of straw and ryegrass catch crops provided a clear and relatively persistent increase in soil organic matter levels, whereas the positive effects on the yield of subsequent wheat crops were modest and transient.  相似文献   

9.
不同粮草复种方式下土壤养分动态研究   总被引：2，自引：0，他引：2  
对6种不同的粮草复种方式下土壤养分的季节变化进行了比较研究.结果表明:冬季种植牧草与种植粮食作物比较降低了土壤pH值、增加了土壤有机质和速效养分,特别是冬季种植多花黑麦草和黑麦明显增加了土壤有机质、碱解N、速效K和速效P含量,促进后作生长,为后季作物增产提供可能性.土壤pH值随土层增加而增加,土壤养分随土层增加而减少.经过一个复种周期,各复种方式土壤pH值稍有提高;有机质、全N、碱解N含量稍有降低,变化不大;土壤速效P和速效K含量有较大幅度的降低.  相似文献   

10.
The establishment of cover crops, in relay, to minimise soil erosion, improve soil physical condition and provide a main-season crop in rotation with potatoes (Solanum tuberosum L.) is a recommended agronomic practice in Atlantic Canada. This is usually achieved by seeding winter rye (Secale cereale L.) or winter wheat (Triticum aestivum L.) immediately after potato harvest for ground cover followed, the next spring, by inter-seeding an annual or biennial forage crop by drilling. Spring drill seeding can, however, be delayed or prevented by wet ground conditions, thus, making broadcast seeding a considered alternative. This study examined, therefore, the comparative merits of spring broadcast seeding and drill seeding of two adapted forages, Italian ryegrass (Lolium multiflorum Lam.) and red clover (Trifolium pratense L.), into a standing crop of fall-seeded winter rye or winter wheat. Crop performance was evaluated, using meter-square quadrats, as ground coverage and grain yield (of cereals). Soil compaction, evaluated as shear strength in the 0–15 cm layer (avoiding wheel tracks) of a fine sandy loam (Orthic Podzol), was greater after drill seeding than after broadcast seeding by a factor of 7.2% and was attributed to the greater ground-contact mass of the drill seeder. The forage crops provided 5.5% more ground coverage with drill seeding than with broadcast seeding. However, seeding method had no effect on the cereal host crops' ground coverage or grain yield. Ryegrass coverage was 123% of red clover coverage and winter rye coverage was 176% of winter wheat coverage. Forage coverage, in this study, suffered no setback because of the greater soil compaction associated with drill seeding. However, soils are subject to greater compaction under wetter conditions, thus, broadcast seeding is expected to be a better option, the wetter the spring.  相似文献   

11.
Two popular concepts of soil fertilization, basic cation saturation ratio (BCSR) and sufficiency level of available nutrients (SLAN), were tested on a calcareous soil (Aeric haplaquept) during 1995–1996 at the Bangladesh Rice Research Institute (BRRI) Regional Station Rajshahi using wheat as a test crop. According to BCSR concept the soil was deficient in potassium (K) and according to SLAN concept it was deficient in phosphorus (P), respectively. Potassium dose of 120 kg ha‐1 [to attain 2% saturation of total cation exchange capacity (CEC) according to BCSR] along with other two doses (0 and 60 kg K ha‐1) and P dose of 50 kg ha‐1 (to attain available P at sufficiency level) along with other two doses (0 and 100 kg P ha‐1) were compared in a randomized complete block design. The application of 50 kg P ha‐1 significantly increased plant height, spikes m2, grains per spike, grain and straw yields of wheat over 0 kg P ha‐1 with or without K but increasing P dose from 50 to 100 kg P ha1 did not give additional yields. The agronomic parameters and yields were not affected significantly by K application. Similar results were also observed in nutrient content and nutrient uptake. Thus, SLAN concept appeared as an effective tool for fertilizer recommendation for the calcareous soil while BCSR gave no apparent result there.  相似文献   

12.
Hu  Zhaoyang  Wang  Yufeng  Fang  Zhigang  Shi  Gaoling  Lou  Laiqing  Ren  Kaidi  Cai  Qingsheng 《Journal of Soils and Sediments》2020,20(2):874-882
Purpose

Growing energy plants in Cd-contaminated soil to produce bioenergy feedstock and remove excess Cd in the soil is a promising approach to the production of sustainable bioenergy feedstock and safe food. Rice, an important staple food for human beings, is a major source of Cd intake in human beings. Italian ryegrass (Lolium multiflorum Lam) is a potential bioenergy plant with high biomass productivity and high biofuel conversion efficiency.

Materials and methods

An Italian ryegrass and rice crop rotation system would be beneficial for the harvest of bioenergy and phytoremediation. An Italian ryegrass–rice rotation system was established in a moderately Cd-contaminated paddy field. The yield of biomass, amount of Cd removal, and transfer factors for three cropping systems (winter fallow, non-cutting, and cutting) were evaluated over 3 consecutive years of field experiments.

Results and discussion

The total biomass production of the Italian ryegrass–rice rotation system was significantly higher than that of the traditional cropping system. Biomass growth was further promoted by cutting during March. No significant differences were found in yield or Cd concentration of brown rice among the different cropping systems. Total Cd accumulation in rice and Italian ryegrass straw in the rotation cropping system was significantly higher than that in the winter fallow cropping system. Cd was mainly accumulated in the roots, and the ability of Italian ryegrass to transport Cd to the leaves was higher than that of rice.

Conclusions

The Italian ryegrass–rice rotation system is a potential cropping system for Cd-contaminated paddy fields. The average annual yield of biomass was 1656.6 kg km?2, and the average annual amount of Cd removal was more than 9.8 g Cd km?2.

  相似文献   

13.
Rice is one of the essential foods of the human diet and advances in agronomic crop management, such as nitrogen (N) rate management, can improve productivity and profitability and reduce adverse environmental impacts. Nitrogen fertilization rates in Chile are generally based on crop yield without considering the soil's capacity to supply it. Five rice soils of the Inceptisol, Alfisol, and Vertisol orders in central Chile were incubated at 20°C for 21 d in the 2011–2012 season, and their N mineralization capacity was determined before sowing the rice crop. These soils were cropped in field conditions with rice fertilized with 0, 80, and 160 kg N ha?1; grain yield, harvest index, and grain sterility were determined. Mineralized N was associated with some chemical properties of each soil, and with the response to N rates in grain yield and grain sterility. Results indicated that the N rates to be used in rice must consider soil N mineralization capacity and crop yield potential. Finally, the best response to the N rates used in this study and the effect on both harvest index and grain sterility was achieved with 80 kg N ha?1.  相似文献   

14.
Organic agricultural systems rely on organic amendments to achieve crop fertility requirements, and weed control must be achieved without synthetic herbicides. Our objective was to determine the crop yield and soil quality as affected by a transition from grass to dryland organic agriculture in the Central Great Plains of North America. This study evaluated three beef feedlot compost(BFC)treatments in 2010–2015 following biennial application rates: 0(control), 22.9, and 108.7 t ha~(-1) on two dryland organic cropping systems: a wheat(Triticum aestivum)-fallow(WF) rotation harvested for grain and a triticale(Triticosecale)/pea(Pisum sativum)-fallow(T/P-F) rotation harvested for forage. The triticale + pea biomass responded positively to the 108.7-t ha~(-1) BFC treatment,but not the 22.9-t ha~(-1) BFC treatment. The wheat biomass was not affected by BFC addition, but biomass N content increased.Beef feedlot compost input did not increase wheat grain yields, but had a positive effect on wheat grain Zn content. Soil total C and N contents increased with the rate of 108.7 t ha~(-1) BFC after three applications, but not with 22.9 t ha~(-1) BFC. Soil enzyme activities associated with N and C cycling responded positively to the 108.7-t ha~(-1) BFC treatment. Saturated salts were high in the soil receiving 108.7 t ha~(-1) of BFC, but did not affect crop yields. These results showed that BFC was effective in enhancing forage yields, wheat grain quality, and soil C and N, as well as specific microbial enzymes important for nutrient cycling. However, the large rates of BFC necessary to elicit these positive responses did not increase grain yields, and resulted in an excessive buildup of soil P.  相似文献   

15.
Nitrogen (N) leaching from soil into water is a significant concern for intensively grazed forage‐based systems because it can cause a decline in water quality and is a risk to human health. Urine patches from grazing animals are the main source of this N. The objective of this study was to quantify the effect that forage type and gibberellic acid (GA) application had on N leaching and herbage N uptake from urine patches on perennial ryegrass–white clover (RGWC), Italian ryegrass and lucerne. A lysimeter study was conducted over 17 months to measure herbage growth, N uptake and N loss to water beneath each of the three forage types with the following treatments: control, urine (700 kg N/ha) and urine with GA (8 g GA active ingredient/ha). Compared with RGWC (205 kg N/ha), N leaching losses were 35.3% lower from Italian ryegrass (133 kg N/ha) and 98.5% higher from lucerne (407 kg N/ha). These differences in leaching loss are likely to be due to winter plant growth and N uptake. During the winter months, Italian ryegrass had higher N uptake, whereas lucerne had lower N uptake, compared with RGWC. The application of GA had no effect on N leaching losses, DM yield or N uptake of forage treated with 700 kg N/ha urine.  相似文献   

16.
An experiment has been carried out in cultivated drainage lysimeters filled with reported soil in order to investigate on the disappearance and mobility of Metolachlor and Terbuthylazine as related to the nitrogen fertilization level. Two experimental units have been compared: in the O-N treatment the soil did not receive N fertilizers during the 7 years previous to the experiment, whereas in the H—N treatment the average application rate of nitrogen during the same period was 220 kg ha?1 year?1; a corn crop has been cultivated in the present experiment. The active ingredients have been analysed in the artificial soil profile (from 0 to 40 cm, by 10 cm soil layers) and in leachates. The disappearance rate of Terbuthylazine was affected by nitrogen fertilization level, as the half life resulted about 7 days higher in O—N (21.9 days) treatment than in H—N (14.6 days). On the contrary, N fertilization did not significantly modify the half life of Metolachlor (17.2 and 15.9 days at O—N and H—N, respectively). A N-dealkylated degradation product of Terbuthylazine has been found in the shallow soil layers. The distribution pattern of herbicides content in the soil profile showed that Terbuthylazine was less mobile than Metolachlor. Leachates did not contain Terbuthylazine at all, but amounts of Metolachlor close to the detection limits (25 μg L?1).  相似文献   

17.
Potassium (K) plays an important role in many physiological and biochemical processes in plants and its adequate use is an important issue for sustainable economic crop production. Soil test–based K fertilizer recommendations are very limited for lowland rice (Oryza sativa L.) grown on Inceptisols. The objective of this study was to calibrate K soil testing for the response of lowland rice (cv. Ipagri 109) to added K. A field experiment was conducted in the farmers' field in the municipality of Lagoa da Confusão, State of Tocantins, central Brazil. The K rates used were 0, 125, 250, 375, 500, and 625 kg K ha?1 applied as broadcast and incorporated during sowing of the first rice crop. Rice responded significantly to K fertilization during 2 years of experimentation. Maximum grain yield of about 6,000 kg ha?1 was obtained with 57 mg K kg?1 soil in the first year and with 30 mg K kg?1 in the second year. This indicated that at low levels of K in the soil, nonexchangeable K was available for plant growth. Potassium use efficiency designated as agronomic efficiency (kg grain produced/kg K applied) decreased significantly in a quadratic fashion with increasing K level in the soil. Agronomic efficiency had a significantly linear association with grain yield. Hence, improving agronomic efficiency with management practices can improve rice yield.  相似文献   

18.
The straw on the soil in the green cane harvesting system acts as a physical barrier to the action of the pre-emergence herbicides. However, some herbicides have physico-chemical characteristics to pass through the straw in water solution. The aim was to evaluate the influence of different densities of sugarcane straw on the leaching of aminocyclopyrachlor in a tropical soil (Oxisol—Typic Hapludox) in a system of green cane harvesting. The experiment was carried out using glass columns filled with soil, with and without sugarcane straw (0, 5, 10, and 20 t ha?1) on the top of the soil. 14C-aminocyclopyrachlor was applied followed by 200 mm of simulated rain for 48 h. The herbicide was detected in all soil layers (0–30 cm), and in the leachate (>?30 cm), in small trace amounts (≤?0.21%) in all treatments, showing that aminocyclopyrachlor undergoes a high degree of leaching in the clayey soil. In the absence of straw, 39% of the herbicide remained in the upper layer (0–5 cm). In the presence of straw, the herbicide was distributed through the soil profile, mainly from 0 to 25 cm. Forty percent more herbicide was retained in the straw with 20 t ha?1 of sugarcane straw. Thus, it is concluded that the straw in high amounts retains aminocyclopyrachlor, but does not prevent it from reaching the soil; the high solubility of the herbicide and intense rainfall in a short period of time are factors that contribute to the herbicide passing through this barrier.  相似文献   

19.
Summary Denitrification activities were measured over a 3-year period in a coarse sandy soil and a sandy loam soil. In all years the crops were spring barley in combination with Italian ryegrass as a catch crop. The denitrification loss was measured using the acetylene inhibition technique on soil cores. Furthermore, a simple model was developed, based on daily values of soil moisture and soil temperature, to calculate the denitrification loss. Soil temperatures for the model were measured, whereas soil moisture was derived from a water-balance model. Measurements of denitrification gave an annual loss of 0.6 kg N ha-1, and the model calculated a loss of 1–2 kg N ha-1 in the coarse sandy soil. In the sandy loam soil annual losses were measured as 1.5, 3.0, and 13.0 kg N ha-1 in 1988, 1989, and 1990, respectively. The corresponding values from the model simulation were 14, 9 and 14 kg N ha-1.  相似文献   

20.
Forage radish is a unique winter cover crop that is relatively new but becoming rapidly adopted in temperate, humid North America. Little is known about how the use of this cover crop may influence subsequent nitrogen availability, soil water accumulation in the soil profile in corn silage production system. In this present work, the average nitrogen uptake by silage corn increased significantly by 11.6% in cover plots compared with the no-cover control plots. The recovery efficiency and agronomic efficiency of applied nitrogen in silage corn declined in cover plots compared to no-cover plots. The average soil water storage in cover plots was significantly higher than in the control after corn sowing and at the harvest stage. With increasing nitrogen application level, the average corn grain yield increased significantly at 56 and 112 kg N ha?1 by 13.1% and 39.8%, respectively. Planting a forage radish cover crop can facilitate growth of silage corn and markedly improve total nitrogen uptake of corn. Consideration should be given to nitrogen application rate and also to avoiding excessive nitrogen input in the subsequent crop following a cover crop, thereby truly improving subsequent fertiliser use efficiency.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号