สืบค้นงานวิจัย
Estimates of Nitrogen Fixation by Leguminous Cover Crops Grown in Immature Rubber Plantations Using 15 N Isotope Dilution Technique
Prasannakumari P. - ไม่ระบุหน่วยงาน
ชื่อเรื่อง (EN): Estimates of Nitrogen Fixation by Leguminous Cover Crops Grown in Immature Rubber Plantations Using 15 N Isotope Dilution Technique
ผู้แต่ง / หัวหน้าโครงการ (EN): Prasannakumari P.
บทคัดย่อ (EN): The beneficial effects of leguminous ground covers on growth and yield of rubber and improving soil properties have been well documented. Leguminous cover crops fix atmospheric nitrogen, enrich soil with organic matter, improve soil fertility, reduce soil erosion and suppress weed growth. Legume covers help in enhancing the growth of rubber during immature phase and reduce the immaturity period. Pueraria phaseoloies and Mucuna bracteata are the two common cover crops grown in rubber plantations in India. Major advantage of growing legumes is their ability to fix atmospheric nitrogen in the root nodules in association with a group of bacteria belonging to the genus Bradyrhizobium. Legume cover crops fix substantial quantity of atmospheric nitrogen and thus help in reducing the use of costly nitrogenous fertilizers. The actual quantity of nitrogen fixed by these two legumes in the traditional rubber growing tract of India has not been estimated. The 15N Isotope dilution method in which labeled N is added to soil has been widely used to provide reliable estimates of N2 fixed by legumes in the field. In the present work. 15N Isotope dilution method has been used to estimate the amounts of N2 Fixed by Pueraria phaseoloides and Mucuna bracteata grown in the inter-rows of immature rubber plantation in the traditional rubber growing tract of South India. Using Ipomea batatas as the reference plant. A field experiment was conducted in the RRII farm duting the active growth period of cover crops, ie from June to November. During the year 2009. in an area planted with Hevea brasiliensis clone RRII 105. The soil of the experimental area was sandy clay loam, with Ph-4.4, organic carbon-1.86 per cent, available P-3.5 mg/kg and available K-26.6 mg/kg, Pueraria phaseoloides and Mucuna bracteata and Ipomea batatas were established in the inter-rows of rubber plants in separate blocks in the same field. The seeds were not inoculated with Bradyrhizobium prior to wowing. Uniform cuttings of Ipomea batatas, (10 cm length), collected from Central Tuber Crops Research Institute. Trivandrum, were planted, at therate of three cuttings per planting point, spaced 15 cm apart. Recommended doses of NPK fertilizers were applied to both cover crops and reference plant. For labeled N application, micro-plots (1m x 1m) were erected using GI sheets, inserted 6 cm into the soil surface in between two rows of rubber plants. There were seven replicate micro-plots for each legume and the reference plant. 15N labeled urea, 5 atom% 15N excess, @ 5 kg/ha was applied in each micro-plot, after the cover and reference plant established well. The labeled fertilizer was dissolved in 1 liter water and then poured with a watering can. The area outside the micro-plot was fertilized with equivalent amounts of non-labeled urea. The micro-plot experiment with labeled urea application was repeated again during August-September and also during October-November. The above ground biomass from the labeled N applied micro-plots were harvested 45 day s after the application. Fresh biomass was weighed at the site and sub samples were collected for estimating dry matter and N content. The plant samples were dried at 70oC in an air draught oven. Weithed for dry matter determination. Powdered and analyzed for tissue N and atom % 15N, Total N in plant tissue was determined by micro-Kjeldahl method and N isotope ratio by Mass Spectrometry. The percentages of plant N derived from the atmosphere (% Ndfa) and from labeled N (% Ndfl) were calculated. The data was subjected to analysis of variance. Dry matter accumulation, N content in dry matter and N accumulation in above ground biomass were comparable for the two legumes. While these parameters were significantly lower for the reference plant Ipomea batatas during all the three measurement periods. 15N enrichment in plant tissue was signkficantly lower for the legumes compared to the reference plant Ipomea batatas. Indicating a dilution of the legume plant N by non-labeled N from the atmosphere, which is an indication of nitrogen fixation by the legumes. The estimate of per cent N derived from fixation (% Ndfa) for P. phaseoloides ranged from 71.07 per cent of total plant N during June-July, to 42.96 per cent during Oct-Nov. period Corresponding estimates of N, fixation for P. phascoloides ranged from 79.82 kg. N/ha during June-July to 39.32 kg N/ha during Oct-Nov. and averaged 58.1 kg N/ha/year. %Ndfa for M. bracteata ranged for 73.27 per cent of total plant N duing Jun-July to 60.13 per cent during Oct.-Nov. and corresponding estimates of N2 fixation ranged from 83.95 kg N/ha during June-July to 57.04 kg N/ha during Oct.-Nov, and averaged 67.7 kg N/ha/year. In our study, N2 fixation by of M. bracteata, was higher than that of P. phaseoloides, and the difference was significant during the Oct-Nov, perild. It has been previously observed that the population of Bradyrhizobium which could nodulate P. phaseoloides in acid soils was low. And the effectiveness of nodules produced was also found to be low. N2 Fixation by P. phaseoloides observed in this study .ie 58.1 kg N/ha iscomparable with the estimate of 49.0 kg N/ha reported earlier in a Malaysian oxisol. Estimated by 15N Isotope dilution method using Ipomea batatas as reference plant. Isotopic estimates of N2 fixation by M. bracteata are not reported, but significantly higher N-accumulation in biomass compared to P. phaseoloides of the same age has been reported. The study showed that both the cover crops fixed considerable quantities of atmospheric nitrogen and that N2 fixation by Mucuna bracteata was higher than that of Pueraria phaseoloides.
บทคัดย่อ: ไม่พบข้อมูลจากหน่วยงานต้นทาง
ภาษา (EN): en
เผยแพร่โดย (EN): การยางแห่งประเทศไทย
คำสำคัญ (EN): N2 fixation
เจ้าของลิขสิทธิ์ (EN): การยางแห่งประเทศไทย
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Prasannakumari P.. "Estimates of Nitrogen Fixation by Leguminous Cover Crops Grown in Immature Rubber Plantations Using 15 N Isotope Dilution Technique". ไม่ระบุหน่วยงาน. ม.ป.ป.

Prasannakumari P.. "Estimates of Nitrogen Fixation by Leguminous Cover Crops Grown in Immature Rubber Plantations Using 15 N Isotope Dilution Technique". ไม่ระบุหน่วยงาน. ม.ป.ป.. Print.



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Estimates of Nitrogen Fixation by Leguminous Cover Crops Grown in Immature Rubber Plantations Using 15 N Isotope Dilution Technique
Prasannakumari P.
การยางแห่งประเทศไทย
ไม่ระบุวันที่เผยแพร่
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