Resource management for optimising tuberisation in Tannia (Xanthosoma sagittifolium(L.) Schott)

Abstract

The research entitled ‘Resource management for optimising tuberisation in tannia (Xanthosoma sagittifolium (L.) Schott)’ was conducted at College of Agriculture, Vellayani, Thiruvananthapuram, during 2019-2023. The objectives of the study were to characterise the tannia growing soils of three agro-ecological units (AEUs), to study the tuberisation pattern of tannia, to assess the effect of soil amendments and nutrient management in tannia, and to work out the economics. The study was undertaken as three experiments. In the first experiment entitled “Characterisation of tannia growing soils” four physical properties, viz., soil texture, bulk density (BD), particle density (PD) and water holding capacity (WHC), 17 chemical properties viz., pH, exchangeable acidity, electrical conductivity (EC), cation exchange capacity (CEC), organic carbon (OC), N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, B and Al, and three biological properties, viz., soil respiratory activity (SRA), total microbial biomass carbon (TMBC) and dehydrogenase activity (DA) of tannia growing soils of three selected AEUs were analysed. The selected AEUs were AEU 8 (Southern Laterites), AEU 9 (South Central Laterites), and AEU 12 (Southern and Central Foothills). The experiment II (Tuberization pattern of tannia) and experiment III (Effect of soil amendments and nutrient management in tannia) were conducted in AEU 9, in a farmer’s field located at Kollam district, Kerala, during the period from February to December 2021. The second experiment was a pot study laid out in CRD with three treatments (t1: Kerala Agricultural University Package of Practices recommendation (KAU POP), t2: Farmer’s practice, t3: Absolute control) and six replications. The nutrient management followed in farmer’s practice was application of lime (350 kg ha-1) as soil amendment along with 25: 25: 50 kg NPK ha-1. The third experiment was laid out in RCBD with (4 x 3) + 1 treatments, replicated thrice. The treatments comprised combinations of soil amendments (a1: dolomite, a2: phosphogypsum, a3: compost + dolomite, and a4: compost + phosphogypsum) and nutrient management [n1: recommended dose of nutrients (RDN) + borax (10 kg ha-1) at 4 MAP + solubor (0.1%) at 5, 6 and 7 MAP, n2: RDN + ZnSO4 (20 kg ha-1) at 4 MAP + ZnSO4 (1%) at 5, 6 and 7 MAP and n3: RDN + borax (10 kg ha-1) + ZnSO4 (20 kg ha-1) at 4 MAP + solubor (0.1%) + ZnSO4 (1%) at 5,6 and 7 MAP], compared against a control (KAU POP). The soil of the experimental site was sandy loam in texture and strongly acidic in reaction (surface soil pH - 5.45; sub soil pH - 5.05). Cormel pieces (100 g) of a local variety were planted at a spacing of 90 cm x 90 cm. Compost, dolomite and phosphogypsum were applied at the rate of 1kg per plant, 80 g per plant and 50 g per plant respectively. Cluster analysis of the three selected AEUs was carried out to group similar panchayats based on their physical, chemical, and biological variation. In the case of physical properties, three clusters were identified. The cluster 1 was heterogenous, including panchayats with high influence of WHC, PD and BD and lesser influence of PD and BD and classified as “moderately suitable for tannia”. The cluster 2 comprised panchayats which had high influence of WHC and lesser influence of PD and BD This cluster was classified as “suitable for tannia”. Majority of panchayats in AEU 8 fell in cluster 3 which was named as “less suitable for tannia” with lesser influence of WHC and higher impact of PD and BD. Cluster analysis of the soil chemical properties revealed three optimum number of clusters. Cluster 1 was influenced with high values of EC, CEC, OC, K, Ca, Mg and S and lower values of pH, exchangeable acidity, Fe, Zn, B, and Al. It was categorised “suitable for tannia”. It was mostly found in AEU 8. The variable P was quite prevalent in the panchayats of AEU 8. Four panchayats of AEU 12 were also included in cluster 1. Regarding cluster 2, categorised as “moderately suitable for tannia” a significant proportion of panchayats within AEU 8 and AEU 9 were found to have elevated levels of exchangeable acidity, P, B, Fe, and K. High presence of exchangeable acidity, and P content were observed in Pallichal, Karumkulam and Venganoor of AEU 8, and Pooyappally of AEU 9. The variables, B and Fe were found to be high in AEU 8 and AEU 9. This cluster also comprised two panchayats of AEU 12, with high influence of available K. Cluster 3 included panchayats with higher influence of pH, Fe, Zn, B, and Al. It was categorised in “less suitable for tannia.” The panchayats covered in AEU 9 exhibited elevated pH, Fe, and B levels. Four panchayats of AEU 12 and one panchayat of AEU 9 had high influence Al and Zn. The study revealed that the tannia growing soils of the selected AEUs could be grouped into three categories (suitable, moderately suitable, and less suitable for tannia) based on the physico-chemical and biological properties of the soil. The Southern and Central Foothills (AEU 12) could be categorised as suitable for tannia, with the panchayat Amboori exhibiting soil properties favourable for cultivating tannia. The rate of tuber bulking in tannia was observed to reach its peak at 4 MAP to 5 MAP. Compared to farmer’s practice, KAU POP showed lesser reduction in the number of roots, root weight and root volume per plant from 6 MAP to harvest, resulting in higher yield. Supplementing KAU POP with basal application of compost (1 kg per plant) and phosphogypsum (50 g per plant), and top dressing with borax (10 kg ha-1) and ZnSO4 (20 kg ha-1) at 4 MAP followed by foliar application of solubor (0.1%), and ZnSO4 (1%) at 5 MAP, 6 MAP and 7 MAP could be recommended for realizing higher yield, starch content, longer shelf-life, and higher net returns of tannia in the South Central Laterites of Kerala.