Current World Environment

Introduction

Recent agricultural practices i.e the use of fertilizers pesticides, herbicides and biocides etc. are employed to increase the soil fertility and crop production to feed an increasing population in a developing country like India. Excessive use of fertilizers by man is one of the major source of environmental pollution.

Fertilizer enriched soil¹ cannot support microbe population. Hence, humus and essential micro and macro-nutrients become efficient in such soils. These soils become poor and can easily be eroded by wind and rain causing more damage to the ecosystem. Long term application of fertilizers on land has also created an adverse ecological effect of aquatic ecosystem because some of them are washed off land into rivers through irrigation, rain etc.^1-2

Successive use of nitrogenous fertilizers to the soil make plants less resistant to disease. The total crop yield increases but there is a decrease in the protein content. It has been found that there is a 25-30% decline in the protein content when corn, maize, gram and wheat are grown on soil fertilized with NPK fertilizers. Balance of amino acid within the protein molecule is disrupted and the quality of protein is thus lowered. Consumption of low quality protein grains lead to malnutrition in human beings. Because of fertilizers use, oversized vegetables and fruits are produced and these are more prone insects and other pests. Chemical fertilizers and made of noly a few minerals and so they impede the uptake of other minerals and imbalance the whole pattern of plant body.

Nitrogenous fertilizers in excess leads to the accumulation of nitrate ion (NO₃^-) in soil which are transferred to man through plants. Nitrate (NO₃^-) being highly soluble go into drinking water and become toxic, when this concentration exceeds 90ppm. Causes diarrhea and cyanosis (blue-Jaundice) in children. In human body these NO₃^- and NO₃^- are converted to nitriso and nitriso amines which are suspected as agents of stomach cancer. The NO₂^- as pollutant enter into blood stream and combine with haemoglobin which causes methaemoglobinamia. Exceeding of NO₃^-concentration from 10% in blood causes “Blue Bady Syndrome” resulting into child’s death.¹

Imbalanced use of nitrogenous fertilizers^3-5 make the soil deficient in micro-nutrients viz. Zn, Co, Fe, Mn, Ni etc. Some of the important factors which are responsible for affecting the soil micro-nutrients are as extensive cultivation of fertilizer responsive high yielding varieties on marginal soil. Large scale deforestation leads to the reduction of organic matter and depletion of soil micro-nutrients.

The adverse ecological effects due to excessive fertilization can be avoided by predecting the mineral nitrogen pool of the soil and nitrogen requirement of the cultivated crops.⁶

Material and Methods

The area under study comprise Badlapur Tahsil of Jaunpur district in Uttar Pradesh. The investigated areas are Arjunpur, Kachhaura, Ratasi, Baharipur and Mahada. In the model farm, two crops namely paddy and maize were put to investigation. The nitrogen content of soil was estimated on adding urea fertilizer before sowing after harvesting the crop by applying Kjeldahl’s method⁷ as used earlier.⁸

Results

The average area of each villages under consideration is 27 hectare. Hence total area covered by all these five villages will be = 27 × 5 = 135ha. About 50% of the total area is covered by gardens, houses, barrel land and other cultivated crops and remaining 50% is cultivated by paddy and maize. Hence, 135/2 = 67.5 ha.

Among the total area about 60% area is cultivated by paddy and 40% by Maize. Hence.
67.5/ 100
60 = 40.50ha
67.5/ 100
40 = 27.00ha

Now, since 64.46 kg/ha nitrogen remains unconsumed by paddy and 54.39 kg/ha by maize. Hence, total unconsumed nitrogen by paddy crop cultivated over 40.50ha = 64.46×40.50 = 2610.63 kg.

Similarly total unconsumed nitrogen by maize crop cultivated.

over 270.0 ha = 54.39 × 27.0 = 1468.53 kg, Grand total = 2610.63 + 1468.53 = 4079.16 kg

Hence,

unconsumed nitrogen/ha = 4079.16/67.5 = 60.432 kg/ha

Table 1: Percent consumption of nitrogen in different crops and its residual values

Discussion

Under field conditions the urea in soil undergoes changes due to biological activities and is converted into ammonium carbonate and them to nitrates. Nitrate and ammonical forms are absorbed by plants and utilized. The conversion of urea into ammonical and nitrate forms take about 7-14 days. Urea application to soil creates a small loss of calcium from the soil.

Due to regular use of nitrogenous fertilizers, study reveals that in paddy on an average 45% and in maize 40% of nitrogen added to the crop remains unconsumed. Generally, without taking pains in analyzing soil the recommended of high concentration of nitrogen in the soil. Some part of it in the form of different compounds dissolve and passes through drains polluting the water bodies like ponds, lakes and rivers. The improportionate soil ingredients disturb it’s texture, structure, physical and chemical properties. Thus, it is recommended that the soil analysis of the plots should be dully done and fertilizers added in requisite amounts. The situation can be well understood from Table 1.

Acknowledgements

The authors are highly thankful to the principal, S.G.R.P.G. College, Dobhi, Jaunpur (U.P.) for providing necessary facilites. Authors owe a lot to agriculture extension department of U.P. (India) for providing experiment facilities and relevant documents.

References
 

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