AN APPROACH TO REJUVENATE THE WASTELANDS OF NORTH-WEST HIMALAYAS THROUGH DUALLY (RHIZOBIUM + VAM) INOCULATED SEEDLINGS OF ROBINIA PSEUDOACACIA

DEGRADED SOIL AND PLANT RESTORATION IN JHALUKBARI HILL SLOPES USING SWEET

During the present investigation, soil from various wasteland sites of different districts of Himachal Pradesh were sampled and their chemical properties such as pH, EC, organic carbon, available N and P were studied in addition to VA-mycorrhizal spores population. In these soils, the growth performance of Robinia was also evaluated. Total of nineteen rhixobial isolates were developed from the nodules of Robinia raised in different wasteland soils and were screened alongwith the four isolates from nursery soils for Robinia. Further, impact of different VAM-fungu at varying levels of phosphorus were also evaluated on the growth of Robinia. The interaction effect between efficient rhizobial isolates and VAM-fungi was studied as a part of development of technology for manufacturing dually inoculated i.e. profusely nodulated and VAM colonized saplings of Robinia.

The wasteland soils of various districts of H.P. varied in their chemical characteristics. The pH of such soils was found acidic to allaline in nature and electrical conductivity varied between 0.036 to 1.614 dsm^-1. In majority of the wasteland soils sampled the organic carbon, available nitrogen and vailable phosphorus status was poor. In general, the wasteland sites studied were steep slopes, having eroded, shallow soils. The stoniness was prevalent in most of the soils. In majority of the soils the population of VA-mycorrhizal spores was higher than that of generally found in cultivated soils.

The performance of Robinia in these wasteland soils under glass-house conditions, was poor except in few soils. Overall the nodulation status was very poor suggesting the lack of sufficient population of specific rhisobia to form the nodules in the Robinia. For normal growth of Robinia or other species in these soils, it is necessary to modify the site in some way.

In contrast to chemical fertilizers, VA-mycorrhizal fungi and N₂-fixing symbionts is a long term proposition for increasing/changing soil fertility as once it is introduced into the soil it will be self sustaining. Although, VAM-fungi and rhizobia are widely distributed, the adverse conditons prevailing at wasteland sites can adversely affect the population either reducing their number or eliminating the efficient strain altogether in which only the unproductive strains survive. Therefore, it is imparative to either conserve the indigenous VAM-population in degraded soils or develop the efficient, competitive inoculum of VAM and rhizobia to ensure the availability of adequate inoculum of the appropriate strain for supporting the growth of tree species. Effectiveness, competitiveness and persistence of introduced Rhizobium in soil is prerequisite for the success of any inoculation programme, especially in degraded/eroded soils.

During the present inversigation, total 19 rhizobial isolates from wasteland soils and four efficient isolates from nursery soils were screened for Robinia. Majority of the rhizobial isolates significantly improved the plant growth in terms of nodulation status, biomass production and total nitrogen. Various rhizobial isolates varied in their efficacies in systhesizing the shoot and root biomass. From this it could be inferred that the selection of Rhizobium isolates for leguminous NFTs shall be made depending upon the situation and objective, whether more root/shoot biomass is required. The isolates efficient in synthesizing more root biomass could be exploited for the rejuvenation of wastelands.

Plants inoculated with mycorrhizal fungi produced higher root colonization at all levels of phosphorus than the uninoculated plants.

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The present project site which is a hill slope was once coverd by lush green forest cover. But due to over use and also abuse the soil now turn unproductive and fallen barren for the last many dacades. The hill slope of the site was covered by some very pernicious weed species only. The site therefore was first made suitable for tree sapling plantations. In the approsimatey two hectares of land 101 tree saplings were planted. The tree saplings belong to fuel wood, medicinal, oil, timber, rubber, fodder yielding plants and also plants of micellaneous uses. Various harbaceous plants were selected and allowed to grow on the soil surface to check soil erosion. The soil nutrients were studied before and at regular intervals of every four months after plantation. Within the three year period of the project the tree saplings grow to a maximum height of 8 meters (Cassia siamea, Leucena leucocephala). Other species also show very encouraging growth. The survival percentage of saplings were more than 95%. The growth (IVI) of associated herbaceous species in the planted as well as adjacent areas were also studied at regular intervals. People of the nearby localities visited the project site and were encouraged to start the same type of works in their localities. The porject works beyond doubt proved that the hill slopes of Jhalukbari hitherto left barran and unproductive can be turned into productive ones. The people of the near by areas already started collecting fodder and thatch grass from the project site.

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