Quality and yield of wheat crop as affected by different zinc application methods and levels

A field trail was performed at new developmental farm, The University of Agriculture Peshawar during winter 2012 to assess quality and yield of wheat crop as affected by different zinc application methods i.e foliar, soil and priming with Zn. In priming wheat (serin-2010) seeds were soaked in 1 and 5 % Zn solution for 16 hours prepared from ZnSO4. In case of foliar application 2.5 and 5 kg haof ZnSO4.7H2O were used whereas in case of soil application, 5 and 10 kg ha of Zn as ZnSO4.7H2O was surface applied before sowing wheat crop. The NP and K were also used as a basal dose @ of 120:90:60 kg harespectively. The result showed that biological yield, grain yield, soil extractable Zn, uptake of phosphorous and Zn were significantly enhanced when Zn was applied as foliar spray @ of 2.5kg ha followed by 5kg ha as compared to soil application and control treatments. Similarly, foliar application of Zn @ of 2.5 kg haresulted in maximum, biological yield (7516.7 kg ha), grain yield (4490 kg ha), soil extractable Zn (1.003 mg kg), phosphorous in leaf tissue (451.36 mg kg) and Zn in leaf tissue ( T6= 46.63 mg kg) followed by Zn application @ of 5 kg ha.Soil application and control treatments resulted minimum biological yield, grain yield, soil extractable Zn, uptake of phosphorous and Zn. From these results it was concluded that quality and yield of wheat crop were significantly enhanced when zinc was applied as a foliar spray @ of 2.5 kg ha as compared to other methods. Foliar spray at @ of 2.5 kg ha is recommended in zinc deficient soils to get better quality and yield of wheat crop.


Introduction
Wheat (Triticum aestivum L.) is the most important crop among cereal belongs to family Poaceae and is considered as a staple food of Pakistan and at world level. It is also one of the major sources of protein and carbohydrates both for human beings and animals. It is grown in Pakistan on an area of 9062 thousand hectares.23.4 million tons is its total production with a 2585 kg ha -1 average yield [1]. Due to unsuitable row spacing and seed rate its yield is low in Pakistan. These two factors are the most important management factors which are affecting wheat agronomic characteristics [2][3][4]. In Khyber Pakhtunkhwa, its average yield is 1565 kg ha -1 and is sown on area of 769.5 hectare with a total production of 1204.5 tons [5]. Zinc is one of the crucial and important elements which are needed in small amount for the growth of plant. Plant absorbs it in divalent form (Zn 2+ ). Various metabolic functions such as Hydrogenase, auxin metabolism, cytochrome Synthesis, and the ribosomal fraction stabilization are stimulated by this element (Tisdale et al., [6]. Plant life processes that is photosynthesis, Synthesis of chlorophyll, metabolism of nitrogen and its uptake is affected greatly by this element. Its deficiency reduces contents of proteins and its synthesis [7]. Zinc deficiency exhibits, necrosis, poor growth and interveinal chlorosis of lower leaves. Due to its deficiency reddish or brownish spot often occurs on the lower leaves which reduce the seed production [8]. Its deficiency is also common where wheat is grown on calcareous soils. As a result of this a large population of the world lacks its adequate nutrition Maqsood et al. [9]. A national survey revealed that in Pakistan its deficiency in 37% of children's and 41% in mothers [10]. Foliar application on wheat crop with different micronutrients is better than the application of soil and it is effectively used to overcome the deficiency in subsoil [11,12].
Objectives of this study is to: Assess the effect of Zn on wheat yield and its uptake under alkaline calcareous soil. To evaluate different application methods viz soil, foliar and soaking of seeds in Zn solution under the given soil and climatic condition.
To investigate proper doses of Zn for the given application methods

Methods and materials
The experiment was conducted at new developmental farm of Khyber Pakhtunkhwa University of agriculture Peshawar, during winter 2012.Before the start of trail a composite soil sample was taken from the experimental site and analyzed for various physico-chemical characteristic besides the concentration of Zn and phosphorous which were 0.896 mg kg -1 and 10.38 mg kg -1 in composite soil sample. Three Zn application methods including seed priming, foliar and soil were used in the experiment. In the seed priming techniques, seeds were soaked in the desired Zn solution (1 or 5 % solution) for 16 hours and then dried back to original moisture level through sun drying. In foliar spray (2.5 Kg ha -1 and 5Kg ha -1 of ZnSO4.7H2O), the plots were first sprayed just with water to know the amount of solution to be needed to cover the entire plot. After knowing the amount of water, the required concentrations were prepared and sprayed in morning. In case of soil application, the required amount (5 and 10 kg ha -1 of ZnSO4) was mixed with soil and then uniformly broadcasted in the treatment plots allocated to soil application. Plot size was 4m x 3m. Sowing was done on flat beds in rows spaced 30 cm. First irrigation was given few days after sowing while the subsequent irrigation was adjusted according to the need of the crop and avoiding the over irrigation strictly. All the other agronomic practices were kept normal and uniform for all the treatments. The basal dose of fertilizer i.e. half of N and full dose of P and K (60, 90 and 60 kg respectively) were applied at the time of sowing while remaining half of N was applied at knee high stage. Data was recorded on the following parameters: AB-DTPA extractable Zn Zn (a micronutrient) was extracted in AB-DTPA solution as explained by Soltanpur and Schawab [13]. Zn concentration was calculated by atomic absorption spectrophotometer (perkin elmer 2138) using cathode lamp of respective element and acetylene gas. The machine was calibrated with standard of the respective element before analysis of said element in AB-DTPA soil solution (Table 1). Zn concentration in leaf tissue 0.5 g oven dry and fully ground leaf sample was taken into 150 ml conical flask and added to it 15 ml of concentrated hydrochloric acid (HCL) and left over night. 5 ml of HCLO4 (per chloric acid) along with two ml of concentrated sulphuric acid (H2SO4) were added to it. Heated it till it was digested, which was proved due to its fumes layering in the given beaker. Heat was given continuously till the disappearance of fume and the liquid became clear. The liquid was cooled and added to it about fifty ml of distill water and filtered it with Watman filter paper-42. The filtrate was collected in 100 ml volumetric flask and made its volume with distil water [14]. Zn was determined after wet digestion by atomic absorption spectrophotometer (perkin Elmer 2138) using cathode lamp of respective element and acetylene gas. The machine was calibrated with standard of the respective element before analysis of said element in AB-DTPA soil solution.
Phosphorous concentration in leaf tissue 0.5 g oven dry and fully ground leaf sample was taken into 150 ml conical flask and added to it 15 ml of concentered hydro chloric acid (HCL) and left over night. 5 ml of HCLO4 (per chloric acid) along with two ml of concentrated sulphuric acid (H2SO4) were added to it. Heated it till it digested which is proved due to its fumes layering in the given beaker. Heat was given continuously till the disappearance of fume and the liquid became clear. The liquid was cooled and added to it about fifty ml of distill water and filtered it with Watman filter paper-42. The filtrate was collected in 100 ml volumetric flask and made its volume with distil water [14]. To measure phosphorous 1 ml sample was taken in 25 ml of volumetric flask and added to it four ml ascorbic acid mix reagent and diluted it up to the mark. Reading was taken when bluish color was produced. Biological yield (kg ha -1 ) Biological yield was determined by harvesting two central rows in each sub plot and then sun dried, weighed and changes into kg ha -1 by formula.

Grain yield (kg ha -1 )
By threshing the dried harvested materials of biological yield grain yield was determined.
To note the grain yield in each treatment the seeds were cleaned after threshing and after that it is changed (kg ha -1 ) by using the given formula as under Grain yield (kg/ha ) = Grain yield (Kg) ×10000 (No of rows)(RxR distance)(Row length)

Results and discussion
The result obtained on soil extractable Zn is given in

Conclusion and recommendation
From these results it was concluded that quality and yield of wheat crop were significantly enhanced when zinc was supplied as a foliar spray at the lower rate of 2.5 kg ha -1 as compared to other methods. Foliar spray at the rate of 2.5 kg ha -1 is recommended in zinc deficient soils to get better quality and yield of wheat crop.