Detrimental Effects Of Indiscriminate Use Of Manureson On Soil Microbes

In present day agricultural practices indiscriminate use of manures, particularly the N and phosphorus, have led to substantial contamination of soil, air and water. Massive use of these manures, other than organic or biomanure or bacterial fertilizer showed detrimental effects on soil microbes, affects the fertility status of soil and also pollutes environment (Youssef and Eissa, 2014). The prolonged use of these often tends to reduction in pH and exchangeable bases, thus making them unavailable to crops and the production loss.

During the last few years, the agricultural practices in India have undergone a major change through diversification and emphasis being given to the sustainable development system. The term the zone adjacent to the root was introduced for the first time by Hiltner (1904).The major influences that the zone adjacent to root microbes of plants become an important tool to protect the health of plants in an ecofriendly manner (Akhtar et al., 2012).These organism can influences plant growth known as plant growth promoting rhizobacteria (Kloepper et al.,1980) and are involved in various biotic activities (Ahemad et al., 2009).

In tea cultivation the major nutrients are provided through manures, other than chemical; N as urea, sulfate of ammonia and calcium ammonium nitrate, phosphorus as rock phosphate and potassium as muriate of potash. Researches on agronomic helped to increase tea production to a great extent. However, the repeated and continuous application of manures, other than organic or biomanure or bacterial fertilizer for decades changed the physical-chemical properties of the soil. There was a reduction in organic matter content of the soil, which in turn decreases the number of good soil microbes, causes soil infertile.

N fixing and PSB are naturally present in almost all soils .However, their population level may not be sufficient to bring out these biological processes to a significant level. Application of efficient isolates of these bacteria is successfully in practice in many crops. Preparations of such beneficial microbes, especially bacteria are commonly known as biomanure or bacterial fertilizers. Or in other words “biomanure or bacterial fertilizers are carrier based preparations containing beneficial microbes in a viable state” and can enhance soil quality and soil nutrient.

A certain group of bacteria and fungi are considered as biomanure or bacterial fertilizers in tea and they are freely available in surface soil and showed a close association with plants. These organisms take nutrients from the plant tissue and in lieu of supply the required N and phosphorus to plants. The Mycorrhiza, N fixing bacteria and phosphate solubilising bacteria are major biomanure or bacterial fertilizers available in tea field soil.

Naturally occurring microflora are the main player of organic farming, comprises of all kinds of useful bacteria, fungi, arbuscular mycorrhizal fungi (AMF), collectively known as PGPR. Sinha et al., 2014 observed that biomanure or bacterial fertilizers maintain the soil environment, which can fix N, act as phosphate and potassium solubilizer, generation of plant growth enhancing substances, antibiotic and organic substances damages in the soil. Application of biomanure or bacterial fertilizers in the form of seed or soil inoculants to take part in nutrient rotation and crop yield was reported (Singh et al., 2011). Generally, 10% to 40% of the applied fertilizer utilized by plants. Microbial inoculants have immense importance in integrated nutrient management systems for sustainable agriculture and healthy environment (Adesemoye and Kloepper 2009).

The narrow zone adjacent to the root can comprise up to 1011 microbial cells per g of soil (Egamberdieva et al., 2008) and more than 30,000 prokaryotic organism that in general, improve plant productivity (Mendes et al.,2013). Azotobacter plays a significant role in the natural N cycle as it possesses a variety of metabolic activities (Sahoo et al., 2014).

Revillas et al., 2000 reported that Azotobacter produce vitamins like thiamine and riboflavin beside N fixation, plant growth regulators like, indole acetic acid (IAA), gibberellins (GA) and cytokines (CK) (Abed El-Fattah et al., 2013) .This genus comprises of a diverse range of species, namely, A. chroococcum, A. vinelandii, A. Beijerinckii, A. Nigricans, A. armeniacus and A. paspali. Wani et al., 2013 reported the use of this genus as biomanure or bacterial fertilizer for several crops. Sahoo et al., 2014 reported that Azospirillum is also a non symbiotic, motile, gram variable and aerobic bacterium that can survive in flooded conditions. It can stimulate the various aspects of plant growth and development (Bhattacharyya and Jha 2012) .

Saikia et al., 2013 has reported that Azospirillum play a role on plant growth and crop yields in the greenhouse and in field trials. Various species of the genus Azospirillum like A. lipoferum, A. brasilense, A. amazonense, A. halopraeferens and A. irakense have been known to improve productivity of various crops (Sahoo et al., 2014). Park et al., 2010 investigated the stress tolerant properties of, Burkholderia vietnamiensis which produces gluconic and 2-ketogluconic acids, and involved in phosphate solubilisation. Sunflower the zone adjacent to root contains Enterobacter and Burkholderia produce siderophores and indolic compounds (ICs) which can solubilize phosphate (Ambrosini et al., 2012).

The beneficial microbes to be used as biofertilizer are generally applied with various carrier materials. Without carrier materials, the applied beneficial microbes will not survive for longer periods. The carrier materials should have high organic matter content, high water holding capacity, neutral pH for the better survival of the organisms. The efficacy as carrier materials of composted coir pith, lignite, organic manure, vermicompost and vermiculite were so far tested both in vivo and in vitro condition.