The burning and disposal of this waste into water channels have become one of the major source of air and water pollution due to production of green house gases. The organic waste which include garbage, paper product and non-biodegradable material like polythene, glass and metals brings about contamination (malfunctioning) of soil. Leaching and run off from these sites can contaminate both surface and ground water. Contaminants include heavy metals as well as soluble and biodegradable materials.
Organic waste material is available in form of cattle dung, urine, litter, crop waste/residues like sugarcane trash, straw, poultry, sheep and goat dropping, waste from fruit and vegetables, press mud from sugar factories, rice husk and dust from textile industries. These organic wastes can be used for building up and maintaining organic matter in soil to conserve soil fertility and to increase the efficiency of applied fertilizers.
Different strategies, like incineration, sanitary landfill and recycling are available to dispose or re-utilize waste produced by human activities. One appropriate way of recycling organic waste is composting. “It is controlled decomposition and appropriate stabilization of blended organic substrates under aerobic condition that allow the development of thermophilic temperature as a result of biologically produced heat”.
Compost is the product of composting process that is effectively free from pathogens, weed seeds and inert contaminants and is fit for an intended purpose. Compost has primary value as fertilizer and secondarily provides benefit of improving physical and microbial soil characteristics.
Recycling organic waste (composting) is one of major solution of reducing the huge piles of organic wastes and converts into value added soil amendment which otherwise is loss and cannot be made available to plants.
Effectiveness of organic waste is enhanced through enriching it with different nutrients, biologically active substances (BAS) like L-tryptophan (LTP), indole-3-acetic acid (IAA), gibberellins (GAs), kinetin and ACC etc. and plant growth promoting rhizobium (PGPR) for sustainable crop production.
As PGPR are capable of producing physiologically active auxins that may have pronounced effects on plant growth and development through enhancing cell division, cell enlargement, vascular tissue differentiation, root initiation, apical dominance, leaf senescence, leaf and fruit abscission, assimilate partitioning, fruit ripening, tropistic responses and flowering.
By using five tonnes of compost, we can save one bag of urea, one bag of super phosphate, 15 kilogram of natural gas (CH4) used in manufacture of urea. In recycling organic waste, we save other resources e.g. by recycling one tonne of paper, we would save 175 pounds of sulphur, 350 pounds of limestone, 60,000 gallons of water, 900 pounds of steam and 225 kilowatt hours of electricity.
In Punjab, only compostable material from urban wastes is estimated to be three million tonnes per annum. Its plant nutrient potential is equivalent to 20,500 tonnes of nitrogen, 3,300 tonnes of phosphorous and 17,800 tonnes of potash besides large quantities of micronutrients.
Chemical fertilizers being crucial input for improving fertility of soil have become an integral part of modern technology for crop production. There is no complete substitute of chemical fertilizers because soil is generally low in organic matter due to low rainfall and high temperature.
On an average, most soil contain less than one per cent organic matter. Application of organic sources ameliorates the micronutrients deficiencies and improves soil productivity by giving dark colour to soil and by increasing soil water retention, chelation, cation exchange capacity, soil pH buffering capacity and interaction with organic chemicals like pesticides and herbicides.
It has been suggested that humic acid present in organic matter increase permeability of cell membrane, which result in increase uptake of water and nutrient elements. However, organic source alone may not be important for providing sufficient nutrients in readily available form. Moreover, continuous and imbalance use of chemical fertilizers have resulted in low fertilizers use efficiency.
Due to high cost and inadequate use of chemical fertilizers in Pakistan crop yield are low compared to other countries. One of best approach to improve these yields is integrated use of mineral fertilizers and recycled organic waste. The mixture of chemical fertilizers and organic manures improve use efficiency of chemical fertilizers and could decrease the use of chemical fertilizers. Combination of enriched composted material plus chemical fertilizers not only improve soil physical and chemical properties but also increase growth yield of crop.
As uncomposted organic material has wider C: N (carbon to nitrogen) ratio than composted organic material. Due to this, chemical fertilizer applied with blended organic material/compost brings about immobilization of applied nitrogen. When organic material was already composted and enriched with nitrogen fertilizer, then the C: N ratio was narrow in finished and enriched compost. Thus composted material was more effective compared to uncomposted material because mineralization in composted material made it rich in available nutrients.
After a series of experiments conducted on maize and other cereal crops at the Institute of Soil and Environmental Sciences, University of Agriculture, (Faisalabad), it was concluded that enriched compost (25 per cent nitrogen in form of urea) plus 50 per cent recommended nitrogen fertilizers treatments increased the growth and yield parameters like plant height (9.4 per cent), fresh biomass (38.7 per cent), fresh straw weight (33.2 per cent), root length (54.9 per cent), no. of grains per cob (43.5 per cent), grain yield (72.6 per cent), 1000-grain weight (53.8 per cent) of maize crop over untreated control.
The results are in general, at par with the treatment where full dose of recommended nitrogen fertilizer was used. So, enriched compost with 50 per cent nitrogen fertilizer showed promising results and saved 25 per cebt of recommended nitrogen fertilizer without compromising much on yield. Furthermore, not only we saved two bags of urea per ha by adding enriched compost at 250 kg per ha in case of maize crop but also reduce pollution hazard. This is novelty of this approach that enriched compost was not used as source of organic matter which is usually applied in tonnes.