Application of different levels of NPK along with soil and foliar application of zinc and boron on yield, quality and nutrient content of cashew nut for increasing quality parameter, in lateritic soil of Konkan

Introduction

Cashewnut is one of the most important dollar earning crop among the horticulture and plantation crops in the country. The total export of cashew kernels from India during 2015-16 was 96,346 MT valued at Rs. 4952.12 Crore (Anonymous 2016) [1] . In India, cashew is mainly grown in Maharashtra, Karnataka, Kerala and Goa along the west coast Tamilnadu, Andhra Pradesh, Orissa and West Bengal along the east coast. Maharashtra is ranking first in area, production and productivity in the country with 1.75 lakh ha area, 1.90 lakh MT production and about 1186 kg ha -1 productivity, respectively. The cashew production in Maharashtra is mainly concentrated in Konkan region particularly in Ratnagiri, Sindhudurg, and Raigad and west part of Kolhapur district. An attempt has to be made by managing strategies which are essential for the successful maintenance of commercial cashew plantation. The nutrients applied to cashewnut orchards are subjected to leaching due to high rainfall. Therefore, nutrient management under such condition deserves proper attention. Therefore, it was decided to choose another way to increase yield per plant by providing nutrients by foliar sprays at different stages with an aim to assess the effect of different levels of inorganic fertilizers with soil and foliar application of Zn and B on yield, quality and leaf nutrient status of cashew nut.

Materials and Methods

The experiment was laid out at Rukhi Block of Irrigation Water Management, Central Experimental Station, Wakawali during May 2016 to April 2017 in Randomized Block Design with four levels of NPK (1.0:0.25:0.25, 1.0:0.50:0.50, 1.5:0.75:0.75 and 2.0:1.0:1.0 kg NPK per tree) with and without soil application of boron through borax @ 50 g + zinc through zinc sulphate @ 125 g/tree or foliar application of boron through borax @ 0.25% + zinc through zinc sulphate @ 0.5% /tree, an absolute control (to judge the fate of native nutrients) comprising thirteen treatments replicated thrice. Two trees were selected for each treatment.Total seventy eight uniform cashew trees of variety Vengurla-4 were selected from the orchard at the slope of the hill. Four levels of NPK (1.0:0.25:0.25, 1.0:0.50:0.50, 1.5:0.75:0.75 and 2.0:1.0:1.0 kg NPK per tree)through urea, single super phosphate and muriate of potash along with FYM @ 40 kg tree -1 and soil application of boron through borax @ 0.25% and zinc through zinc sulphate @ 0.5% were applied in corresponding treatments in the month of June 2015. The spraying of boron through borax @ 0.25% and zinc through zinc sulphate @ 0.5% in the pertinent treatments (T 10 to T 13 ) were under takenat time of flowering and nut setting stage in June 2016.The boron and zinc solutions for foliar application were prepared by using borax @ 0.25% and zinc sulphate@ 0.5% /tree fertilizer by dissolving the respective weight of chemical fertilizers in 1L of water by continuous stirring. Further, insecticides (Endosulphon, rogar and carboxyl) were also added to these spraying solutions for control of pest incidence. The spraying wascarried out early in the morning by using Gatoorpump. The cashew nuts were picked when the cashew apple were fully ripened and harvested in 5-6 picking.

Results and Discussion

22.36 to 57.97 percent increase in the yield of cashew nut was recorded with the application of different levels of inorganic fertilizers with soil and foliar application of Zn and B significantly increased the yield of cashew nut per tree over the absolute control i.e. no fertilizer application. The yield of cashew nut varied from 7.19 to 10.38 kg tree -1 and the number of nut per kg varied from 138 to 142 kg -1 (Table 1).Application of recommended dose of fertilizer + soil application of boron through borax @ 50 g + zinc through zinc sulphate @ 125 g/tree (treatment T 6 ) recorded the highest cashew nut per tree (10.38 kg tree -1 ), which was at par with the treatment T 4 (1.5:0.75:0.75 kg NPK), T 5 (2.0:1.0:1.0 kg NPK), T 7 (1.0:0.50:0.50 kg NPK + Soil application of B + Zn), T 8 (1.5:0.75:0.75 kg NPK + soil application of B + Zn), T 9 (2.0:1.0:1.0 kg NPK + Soil application of B + Zn), T 10 (1.0:0.25:0.25 kg NPK + Foliar application of B + Zn), T 11 (1.0:0.50:0.50 kg NPK + Foliar application of B + Zn), T 12 (1.5:0.75:0.75 kg NPK + Foliar application of B + Zn)and T 13 (2.0:1.0:1.0 kg NPK + Foliar application of B + Zn). No specific trend of increase in the yield of cashew nut per tree with the increasing doses of NPK was observed during both years of experimentation. But, it is clearly evident from the above results that both zinc sulphate and boron either by soil application or by foliar application had stimulating effect on fruit yield. In this connection, Lakshmipathi et al. (2014) [6] explained that zinc influences flowering and fruit set through its role in auxin biosynthesis as auxins play a major role in flowering and fruit set. Sexual reproduction is more sensitive to low B than vegetative growth and marked reduction in fruit set can occurs without expression of B deficiency symptoms in vegetative parts. Maintaining high B levels in reproductive parts in a vital component of efficient B management for yield in horticultural crops (Raja 2009) [3] . The improvement of yield due to micro-elements may be ascribed to better photosynthesis, less fruit drop, improved fruit size and fruit weight (Singh 2012) [11] . Beneficial effect of nitrogen in increasing the nut yield may be due to the fact that the higher level of nitrogen application in soil in the from urea increase the activity of the enzyme urease (Harishu kumar et al. 1985) [4] which is responsible for hydrolysis of urea to ammonia, readily available to plant (Webset et al. 1955) [13] . Nitrogen being the component of amino acid, nucleotide, nucleic acid, number of co enzyme, auxin and cytokinnis can induce cell elongation, enlargement and development and thereby improved the nut production. Nitrogen also help to synthesis of carbohydrate (Raheja 1971) [9] the protein and other metabolism (Kanwar 1976) [5] resulted increase nut weight. Potassium plays a vital role in the formation or synthesis of amino acid and proteins from ammonium ions which are absorbed from the soil (Raheja 1971) [9] . It also plays an importance role in the maintenance of cellular organization by regulating the permeability of cellular membranes and keeping the protoplasm in a proper degree of hydration by stabilizing the emulsion of highly colloidal particles (Kanwar 1976) [5] . Nitrogen in combination with the phosphorus (NxP) and potassium (NxK) significantly improved the nut yield. It is known that nitrogen acts as a regulator for the utilization of phosphorus and potassium in the plants (Bukman and Brady 1969) [2] . Protein content in the kernel varied from 19.48 percent to 26.42 percent. Significantly highest protein content (28.41%) was observed in the treatment T 12 where application of NPK fertilizer levels + foliar application of boron through borax @ 0.25% + zinc through zinc sulphate @ 0.5% per tree, but this treatment was at par with T 5 (2.0:1.0:1.0 kg NPK), T 8 (1.5:0.75:0.75 kg NPK + Soil application of B + Zn), T 11 (1.0:0.50:0.50 kg NPK + Foliar application of B + Zn) and T 13 (2.0:1.0:1.0 kg NPK + Foliar application of B + Zn).The beneficial effect of foliar spray of boron through borax @ 0.25% + zinc through zinc sulphate @ 0.5%, per tree on fruit quality were attributed to their vital role in stimulating both cell division as well as biosynthesis and translocation of organic food in favors of enhancing growth and fruiting of tree (Sarrwy et al. 2010) [10] . Tandon (1992) [1] , in addition to this, reported the positive interaction of N and S in plant as both these nutrients are vital constituents of protein. The oil content in the kernel varied from 37.17 to 42.97 percent. The treatment T 12 (application of NPK fertilizer levels + foliar application of boron through borax @ 0.25% + zinc through zinc sulphate @ 0.5% per tree) produced significantly higher oil content (51.00%) in kernel, over T 1 , T 2 , T 6 , T 7 , T 8 , T 10 and T 3 , but observed to be at par with T 3 (1.0:0.50:0.50 kg NPK), T 4 (1.5:0.75:0.75 kg NPK), T 5 (2.0:1.0:1.0 kg NPK), T 9 (2.0:1.0: Similar ranges of N, P, K, Fe, Mn, Zn, Cu and B content in cashew kernel of cashew Cv. Vengurla-4 grown on lateritic soils of Konkan were reported by Palsande (2011) [8] . The treatment T 12 (application of NPK fertilizer levels + foliar application of boron through borax @ 0.25% + zinc through zinc sulphate @ 0.5% per tree) showed highest N (4.90%), P (1.19%) and K (0.870%) in cashew kernel. Significantly highest Fe content (204.50 mg kg -1 ), Mn content (34.83 mg kg -1 ), Zn content (23.20 mg kg -1 ), Cu content (22.63 mg kg -1 ), B content (43.03 mg kg -1 ) was observed in treatment T 13 , where 2.0:1.0:1.0 NPK kg/tree + foliar application of boron through borax @ 0.25% + zinc through zinc sulphate @ 0.5% was applied. No fertilizer application or absolute control (Treatment T 1 ) associated with the lowest micronutrient content in cashew kernel.

Conclusion

By considering the higher yield of cashew nut, protein and oil content, NPK and micro-nutrient (i.e. Fe, Mn, Cu, Zn and B) content in cashew kernel, application 1.0:0.50:0.50 kg NPK per tree along with spraying of foliar application of boron though borax @ 0.25% + zinc through zinc sulphate @ 0.5% was to be beneficial in lateritic soils of Konkan.

References

1. Anonymous. Annual Report and Accounts 2015-16. The Cashew Export Promotion Council of India; Cashew Bhavan, Mundakkal, Kollam, Kerala; c2016.
2. Edward Raja M. Importance of micronutrients in the changing horticultural scenario in India. J Hortl Sci. 2009;4(1):1-27.
3. Harishu Kumar P, Khader KBA. Root proliferation in cashew seedlings as influenced by soil texture. Indian Cashew J. 1985;15(2):7-14.
4. Ohler JH. Selection and breeding. Cashew Commun. 1979;71:87-92. Department of Agril. Res. Amsterdam.
5. Sarrwy SMA, Mohamed EA, Hassan HSA. Effect of foliar spray with potassium nitrate and mono-potassium phosphate on leaf mineral content, fruit set, yield, and quality of Picual olive tree growth under sandy soil conditions. Am Eurasian J Agric Environ Sci. 2010;8(4):420-430.
6. Singh PC, Gangwar RS, Singh VK. Effect of micronutrient spray on fruit drop, fruit quality, and yield of Aonla cv. Banarasi. Hort Flora Res Spectrum. 2012;1(1):73-76.
7. Webster GC, Varner JE, Ganse AS. Conversion of carbon-14-labeled urea into amino acids in leaves. Plant Physiol. 1955;30:372.