Current World Environment

Introduction

Waste water is generated in bulk quantity from both domestic as well as industrial estates and its crude disposal is posing a tremendous threat to environment. In developing countries including India, wastewater is commonly a choice for irrigating agricultural field.¹ Globally, approximately 20% of manufactured nitrogen and phosphorous is contained in domestic wastewater² and it has been considered as low price fertilizer because of its high N, P and K content.³ Waste water being rich in organic matter and also contains appreciable amounts of macro and micro-nutrients.⁴ Accordingly nutrients levels of soil are expected to improve considerably using continuous irrigation with waste water.^{5,6,7,8,9,10,11} Thus, recycling of wastewater shall pave avenues in agricultural industry in terms of minimizing the use of inorganic fertilizers whose long-term utilization pose negative pressures on natural environment. The main objective of this experiment was to estimate the growth performance, quality parameters and yield responses of Capsicum annum var. Nishat-1 when irrigated with domestic wastewater. Moreover, effect of wastewater fertigation on the physicochemical parameters of soil and plant nutrients was studied to investigate the prospects of its safe use.

Materials and Methods

Study Area

The experimental field at FoA Wadura, SKUAST-Kashmir, was used during summer (Kharif) 2012 and 2013. The study area falls in 34⁰ 20^/ 55.72”N and 74⁰ 24^/ 6.26”E at an altitude of 1580 m a.s.l. Temperate climatic conditions prevail in the area with mean maximum and minimum temperature as 26.08⁰C and 11.78⁰C respectively. The average precipitation recorded during the experimentation was 628.4 mm and 926.2 mm in 2012 and 2013 respectively.

Experimental Design and the Crop

The different concentrations of wastewater were used along with recommended doses of fertilizers to study the growth, yield and quality of Capsicum annum var. Nishat-1. The experiment was laid in completely randomized block design and involved six treatments replicated thrice (T1: Recommended dose of fertilizers; T2: 100% Grey water; T3: 100% Black water; T4: 50% Grey water + 50% RDF; T5: 50% black water + 50% RDF; T6: 50% black water + 50% Grey water) along with an untreated control (C) irrigated with fresh water. The fertilizers N, P and K were applied as per package and practice prevailing in the university at the rates of 120, 90 and 40 (kg ha^-1), as urea, DAP and MOP respectively. The crop was grown in plots measuring 1.74 × 2.3 m with 45 cm spacing between the plants and 60 cm between the rows. The grey water and black water for irrigation was obtained from the hostels of the university campus and stabilized in open tanks for 20-25 days before being put to use.

Water Analysis

Physicochemical parameters viz; pH and EC were accomplished by following the method of Piper.¹² On the other hand estimation of N, P, K, alkalinity, Ca, Mg, Zn, Cu, Mn, Fe, Cd and Ni of the waste water samples were done by following the methods given by APHA.¹³

Soil Analysis

Composite soil samples were collected from each plot at the depth of 0-30 cm before transplantation and after harvest. Samples were oven dried, ground, sieved and analysed for pH, EC,¹² total N,¹⁴ available P,¹⁵ organic carbon¹⁶ and exchangeable Ca, Mg and K using the ammonium acetate method.¹⁷ Zn, Mn, Cu, Fe, Ni and Cd were analysed by using atomic absorption spectrophotometer, after proper standardization. The soils are deep imperfectly drained, calcareous fine silty texture on nearly level slopes with loamy surface and slight flooding, the soils belong to the order of Inceptsols, with aquepts sub order Haplaquepts great group and Typic Haplaquepts sub group.

Crop Yield and Plant Tissue Analysis

Photosynthetic pigments in the foliage were estimated¹⁸ and fruit samples were harvested from each plot, oven dried for 2 days at 70⁰C, powdered in a grinder and subjected to chemical analysis for the estimation of carbohydrate,¹⁹ protein²⁰ and ascorbic acid contents.²¹ Fruit samples were also analyzed for TSS by using Refractometer. Plant nutrients were determined wet oxidation method using 3:1 ratio of HNO₃: HClO₄.²² Total N was determined by Kjeldahl method,¹⁴ P by spectrophotometer, K by flame photometer. Ca, Mg, Zn, Fe, Mn, Cu, Cd and Ni were estimated by atomic absorption spectrophotometer. Total weight of fruits (kg/plot) at each picking was added to obtain the total fruit yield per plot and expressed as quintals per hectare (q ha^-1). Pooled data of the two years recorded during the experiment was subjected to ANOVA, followed by least significant difference (CD, p ≤ 0.05) using R software statistical package.²³

Results and Discussion

Water Chemistry

Data regarding the physicochemical characteristics of black, grey and fresh water are presented in Table 1. The values were in lower levels than those permitted for upper threshold set of irrigation water and safe reuse in agriculture. According to PCB,²⁴ pH of wastewater should range between 6.5 and 8.5 and EC should not exceed 2.25 dS/m. Our study show that both these parameters of wastewater were within range. Alkalinity, phosphate, Na, Ca, Mg, Zn, Cu, Fe, Mn and Cd were found higher in grey water compared to black and fresh water while as Cl, Fl, SO₄, NH₄ and K were found in higher concentration in black water. The concentration of Ni and Pb did not show any significant variation. However, all the parameters were within permissible limits.

Table 1: Physicochemical Characteristics of Irrigation Water.

Physio-Chemical Characterization of the Soil

Texture of the soil was loamy and the soil pH of various treatments ranged from 6.70 to 7.56 while EC ranged from 0.20 to 1.10. It is evident form the data that various waste water treatment slightly changed the pH of the soil as also reported earlier²⁵ (Table-2). Significant increase in EC was also detected in soil after the experiment^{26,27,28,29,30} which might be due to the relatively higher EC of waste water and formation of metallic salts-complexes of organic matter and heavy metals.³¹ Compared to initial status, the level of N and P exhibited elevated trends in various waste water treatment which can be attributed to the higher concentration of the macronutrients in grey as well as black water On the other hand lower level of Ca and Mg were observed in waste water compared to initial statues of the soil.