Effect of Vermiculite as an Ameliorant for Paper Mill Effluent Irrigated Soil and on the Productivity of Sunflower

INTRODUCTION

Vermiculite is the geological name given to a group of hydrated laminar minerals that are magnesium-aluminum -iron silicates with a suggested formula of (Mg, Fe⁺², Al)₃ (Al, Si)₄ O₁₀ (OH)₂. 4H₂O (Fleisher and Mandarino, 1991). Vermiculite is the member of the phyllosilicate mineral group and is micaceous in nature. Flakes of raw vermiculite concentrate are mica-like in appearance and contain water molecules within their internal surface. The word vermiculite is derived from the Latin word meaning to breed worms, alluding to the worm-like shape resulting from its expansion on heating. Vermiculite can absorb such liquids as fertilizers, herbicides and insecticides which can then be transported as free-flowing solids (Harben and Kuzvcort, 1996). Vermiculite, which is available in plenty in mines is very light in weight (90-160 kg m^-3), has high water holding capacity (150%) and high cation exchange capacity of 120-130 m.eq/100 g (Jasper, 1981). This precious low cost natural resource with its above favourable qualities could be exploited for treating the wastewater and for remediating soils.

The pulp and paper mill, industry ranks high both in terms of water usage and pollution loads. In India, at present, there are about 350 paper mills in operation with an installed capacity of 3.04 x 10⁶ tonnes of paper per annum. It is estimated that 205-315 m³ of water is required per ton of paper made and practically the entire quantity reappears as effluents. The coloring materials present in the wastewater is organic in nature comprising of wood extractives, tannins, resins, synthetic dyes, lignin and its degradation products formed by the action of chlorine or lignin (Rao and Dutta, 1987). Discharge of coloured pulping effluents to the receiving waters inhibits photosynthetic activity of aquatic biota (Walden and Howard, 1981).

In Tamil Nadu, 24 lakh ha (23.97% of total geographical area) of agricultural lands are highly permeable in nature. In this type of soils, water holding and nutrient retention capacities are low. Similarly, the soils (covering an area of 7.54 lakh ha) are facing the problem of sodicity, aeration and drainage which limit the crop productivity. These soil physical constraints could be improved by the application of vermiculite as an amendment (Jasper, 1981). Hence the present investigation was contemplated to evaluate the effect of vermiculite application along with gypsum and press mud with graded doses of NPK fertilizers in degraded soil on sunflower crop.

MATERIALS AND METHODS

A Field experiment was conducted at Pappampalayam, Erode, Namakkal District, Tamil Nadu.

Table 1:	Description of the treatments

Table 2:	Vermiculite and amendments on productive parameters of sunflower under treated paper mill effluent irrigation

Calculated amounts of the amendments as per the treatments including the vermiculite (Raw vermiculite grade 2) were uniformly spread in the plots and ridges and furrows were formed. Sunflower seeds (CO₄) were sown on 02.03.2004 adopting a spacing of 60x45 cm. Top dressing of NPK was carried out and need based irrigation scheduling has been done. The experiment was laid out in randomized block design with three replications (Table 1).

The pH of the experimental soil was 8.18, whereas the EC was 0.41 dS m^-1. The soil available nutrients were 186, 11.7 and 299 kg ha^-1 for nitrogen, phosphorus and potassium, respectively. The organic carbon content was 0.49% in the experimental soil. The Exchangeable Sodium percent (ESP) of soil was 15.1. Yield attributes such as single head weight (g), head diameter (cm), 1000 grain weight: 1000 grain of each representative samples were recorded for each treatment and expressed in gram. Sunflower seeds yields were recorded in each treatment (Table 2 ) and statistically analyzed (Panse and Sukhatme, 1978).

RESULTS

Yield characters: The weight of single head ranged from 154 (T₁) to 306 g (T₅), the later was significantly superior from the rest of the treatments. It was followed by T₈ which registered 294 (Table 2).

Among the treatments, the head diameter ranged from 9.35 (T₁) to 15.6 cm (T₅) which was significantly superior from the rest of the treatments. It was followed by T₇ which registered 14.4 cm (Table 2).

The 1000 grain weight ranged from 40.0 (T₁) to 58.3 (g) (T₅). The highest value in T₅ was followed by T₆ (53.3 g) (Table 2).

The grain yield among the treatments ranged from 1152 to 1934 kg ha^-1. The treatment T₅ which received 5 t ha^-1 of vermiculite and 50% Gypsum (T₅) was significantly superior from the rest of the treatments and recorded the highest grain yield of 1934 kg ha^-1. The treatment T₅ was followed by T₇ (1841 kg ha^-1). The lowest grain yield was recorded in T₁ (control) (1152 kg ha^-1) which was followed by the T₄ (vermiculite at the rate of 10 t ha^-1) and T₃ (vermiculite at the rate of 5 t ha^-1) which recorded grain yields of 1248 and 1333 kg ha^-1, respectively (Table 2).

Soil available nutrients: It was observed that as the stages progressed the available nitrogen content decreased. The lowest available nitrogen content was at harvest stage (179 kg ha^-1) and all different stages were significantly different among themselves.

The highest available nitrogen of 207 kg ha^-1 was observed in treatment T₇ which received (vermiculite at the rate of 10 t ha^-1 + pressmud 12.5 t ha^-1) followed by T₇ (205 kg ha^-1) which were significantly different among themselves and from the rest. The lowest available nitrogen of 167 kg ha^-1 was observed in T₁ (control).

Among the interactions it was observed that T₈ and T₉ of vegetative stage with available nitrogen contents 210 and 209 kg ha^-1, respectively were the highest and were on par with each other while being significantly different from the rest. The lowest available nitrogen of 164 kg ha^-1 was observed in T₁ (control) under flowering stage (Table 3).

The available phosphorus content of vegetative stage 19.8 kg ha^-1 was the highest and it significantly differed from the flowering stage and harvest stage which recorded 18.4 and 16.8 kg ha^-1, respectively. Among the significantly different from the rest of the treatments. The lowest was observed in T₁ (control) with 16.1 kg ha^-1 which was on par with T₃ which was 16.2 kg ha^-1 which was on par with T₃ which was 16.2 kg ha^-1.

Table 3:	Vermiculite and amendments on available nutrient status of soils after harvest under sunflower crop grown with treated paper mill effluent irrigation

Among the interactions it was observed that the treatment T₈ (25.5 kg ha^-1) in vegetative stage recorded the highest and it was significantly different from the rest. The lowest available phosphorus of 14.5 kg ha^-1 (T₁) which was on par with T₃ (14.6 kg ha^-1) in harvest stage was observed.

It was observed that as the stages advanced available potassium content decreased. It was 324 kg ha^-1 in vegetative stage and 313 kg ha^-1 in harvest stage. Among the treatments it was observed that T₈ (338 kg ha^-1) and T₇ (336 kg ha^-1), respectively were the highest and were on par with each other and together they were significantly different from the rest of the treatments. The lowest available potassium content of 302 kg ha^-1 was observed in T₁ (control) and it was significantly different from the rest of the treatments. The interaction between the stages and treatments was non-significant (Table 3).