Diagnostic standards for compositional nutrients in banana cv. nendran for southern laterites of Kerala

Abstract

An exploratory research work entitled "Diagnostic standards for compositional nutrients in banana cv. Nendran for Southern laterites of Kerala" was undertaken in Department of Soil Science and Agricultural Chemistry from December 2023 to October 2024 to formulate Compositional Nutrient Diagnostic (CND) standards for the identification of nutrient imbalances in the banana cultivar Nendran. The objective of the study was to develop CND norms to assess the nutrient imbalance in Nendran variety of banana for Southern laterite soils of Kerala (AEU 8). Geo-referenced soil samples were collected from the surface (0-15 cm) and subsurface (15-30 cm) layers of banana fields across 120 locations from 24 panchayats of AEU 8 viz., Parassala, Karode, Chenkal, Kulathoor, Thirupuram, Poovar, Perumkadavila, Kollayil, Kunnathukal, Athiyanoor, Aryancode, Kanjiramkulam, Kottukal, Vizhinjam, Venganoor, Pallichal, Vilappil, Malayinkeezh, Maranalloor, Kalliyoor, Balaramapuram, Vilavoorkal, Kattakada and Karakulam. Corresponding one-twenty plant samples were collected from the index leaves of banana plants at each location. The chemical analysis of soil samples showed that the surface soil pH ranged from 5.78 to 6.89, averaging 6.28, while the subsurface pH varied between 5.55 and 6.57 with a mean value of 6.08. Electrical conductivity values recorded varied from 0.16 to 0.60 dS m-1 for surface soil and 0.13 to 0.51 dS m-1 for subsurface soil. Organic carbon content ranged from 0.75 to 1.53 per cent in surface soil and from 0.58 to 1.63 per cent in subsurface soil, with the surface soil generally showing higher levels. The pH, electrical conductivity, and organic carbon content all showed a decrease with soil depth. Available nutrient content generally decreased with depth. The available nitrogen content in surface soil ranged from 253.38 to 481.69 kg ha-1, while in subsurface soil, it varied between 213.24 and 461.61 kg ha-1. Phosphorus availability in surface soil exhibited a range from 16.94 to 79.09 kg ha-1 whereas in subsurface soil it ranged from 14.37 to 71.64 kg ha-1. In the surface soil potassium had an average availability of 224. 46 kg ha-1 while in subsurface soil availability fell between 141. 12 and 226.24 kg ha-1. Calcium content in surface soil ranged from 190 to 386 mg kg-1 while in subsurface soil it varied between 154 and 336 mg kg-1. Magnesium levels in 148

surface soil were between 56 and 132 mg kg-1 compared to 39.6 to 103.2 mg kg-1 in subsurface soil. Sulphur content ranged from 17.4 to 30.60 mg kg-1 in surface soil and from 14.40 to 20.32 mg kg-1 in subsurface soil. Available iron content of surface soil ranged between 7.69 and 48.55 mg kg-1 and that of subsurface soil varied from 7.21 to 44.97 mg kg-1. Manganese levels exhibited a mean value of 22.50 mg kg-1 in surface soil and 19.86 mg kg -1 in subsurface soil. Zinc content was found a range from 2.10 to 9.92 mg kg-1 in surface soil while in subsurface soil it varied from 3.10 to 8.85 mg kg-1 averaging 4.05 mg kg-1. Available copper in subsurface soil ranged from 1.10 to 3.42 mg kg-1 and in surface soil it varied between 1.20 and 3.53 mg kg-1. Boron content in surface soil varied between 0.81 and 0.32 mg kg-1 while in subsurface soil it ranged from 0.27 to 0.69 mg kg-1. Available nickel ranged from 1.36 to 7.05 mg kg-1 in surface layer and 1.28 to 5.55 mg kg-1 in subsurface layer while molybdenum values exhibited a mean value of 0.29 mg kg-1 in surface layer and 0.28 mg kg-1 in subsurface layer. The nutrient composition of banana leaves in AEU 8 was analyzed revealing nitrogen levels between 2.05 and 4.36 per cent, phosphorus levels from 0.15 to 0.25 per cent, Potassium ranged from 1.35 to 2.85 per cent and calcium varied between 0.42 and 0.75 per cent. Magnesium showed a range from 0.15 to 0.24 per cent and sulphur content ranged from 0.53 to 0.69 per cent. Iron concentrations were between 150.20 and 223.30 mg kg-1, manganese content ranged from 129.0 to 308.70 mg kg-1, zinc from 10.92 to 16.67 mg kg-1 and copper between 3.60 and 14.20 mg kg-1. Boron levels ranged from 8.80 to 23.60 mg kg-1. Nickel content in plant samples ranged from 0.92 to 3.73 mg kg-1 while molybdenum varied between 0.86 to 3.07 mg kg-1.The average banana bunch yields per panchayat varied from 9.63 kg plant -1 to 14.00 kg plant-1 with an overall average of 11.04 kg plant-1. Following the procedure by Parent and Dafir (1992), CND norms were developed. The nutrient content in banana leaves were first converted to percentages. Then, nutrient concentrations, residue values, simplex, and row-centered log ratios were calculated. The database was then divided into two sub-populations using the Cate-Nelson procedure, based on ranked yield values. The cumulative variance ratio is calculated by combining variance ratios at each iteration. This cumulative variance ratio function, FiC (VX), is expressed as a proportion of the total sum of variance ratios across

all iterations. For yield Y, FiC (VX) exhibited a cubic pattern, with the inflection point indicating a change in model concavity, as identified by the second derivative. The yield cut- off value is determined at this inflection point. To classify a high and low yield subpopulation, the highest yield cut-off value was derived from cumulative values of the variance ratio for each nutrient. The maximum yield cut-off value was found for nitrogen which was 12.29 kg plant-1. CND norms are formulated by calculating the means and standard deviations of row-centered log ratios (VX) of nutrients in high-yield groups, denoted as V*N, V*P, V*K, etc., as well as their corresponding standard deviations (SD*N, SD*P, SD*K, etc.). The computed CND norms are as follows: V*N = 4.15± 0.35, V*P= 1.52± 0.16, V*K = 3.88± 0.32, V*Ca = 2.46± 0.33, V*Mg = 1.44± 0.21, V*S = 2.60± 0.18, V*Fe = -0.95± 0.19, V*Mn = -0.89± 0.27, V*Zn = -3.50± 0.17, V*Cu= -4.10± 0.38, V*B= -3.4± 0.51, V*Ni= -5.36± 0.37, V*Mo= -5.37± 0.28, V*Rd= 7.60± 0.11. The CND indices (IX) are computed using row-centered log ratios of the survey population VX, V*X, and SD*X values. These indices can be either positive or negative. Nutrient indices close to zero indicate an ideal nutrient balance. Negative values of CND indices suggest a deficiency of that nutrient with lower values indicating a greater deficiency. The CND indices calculated for banana cv. Nendran for AEU 8 (Southern laterites) are, IN = 0.20, IP = 0.30, IK = -0.03, ICa = 0.02, IMg = -0.58, IS = 0.06, IFe = 0.14, IMn = 0.19, IZn = 0.78, ICu= -0.12, IB = -0.15, INi= 0.19, IMo = -0.30 and IRd = -0.81. The calculated CND indices revealed magnesium as the most limiting nutrient, establishing the order of limiting nutrients as Mg > Mo > B > Cu > K > Ca > S > Fe > Mn > N > P > Zn.