Performance potential of organic amendments derived from invasive aquatic weed, Limnocharis flava (L.) Buchenau

Abstract

The study entitled “Performance potential of organic amendments derived from invasive aquatic weed, Limnocharis flava (L.) Buchenau” was conducted at College of Agriculture, Vellayani and Integrated Farming System Research Station, Karamana during the period 2022-24. The objectives of the study were production of different organic amendments from the aquatic weed, Limnocharis flava and assessment of their impact on soil health and productivity of okra. Different amendments viz., ordinary compost (OC), vermicompost (VC), microbial compost using solid inoculum (SMC), microbial compost using liquid inoculum (LMC) and biochar (BC) were produced and evaluated. The amendments produced were characterized for physical, electro chemical, chemical and biological properties. The mean residence time for BC production was 1-2 hr. at 300-400 °C and the recovery percentage was 26.16. Recovery % for OC, VC, SMC and LMC were 8.40, 15.10, 11.05 and 12.22, respectively, while composting period was 78, 62, 59 and 50 days. BC recorded the bulk density (0.33 Mg m-3), water holding capacity (261.33 %), pH (9.25), EC (6.42 dS m-1), CEC (13.75 cmol (+) kg-1), AEC (8.72 cmol (-) kg-1), total organic carbon (74.89 %) and C:N ratio (82.39). The highest N (2.14 %) content and lowest C:N ratio (32.32) were obtained for VC. P content (0.73 %) was highest for LMC. K, secondary nutrients (Ca, Mg, S) and micronutrients (Fe, Mn, Zn, Cu and B) were also highest for BC. Heavy metal content was below the detectable level in both source material and the amendments produced. A field experiment was conducted to study the effect of different organic amendments on soil health and crop productivity using okra (variety: Salkeerthi) as the test crop. The treatments included amendments produced @ 25 t ha-1 along with 100 and 75 % of recommended dose of fertilizers (RDF), FYM @ 25 t ha-1 along with 100 % RDF and absolute control. The different amendments had significantly influenced the biometric and yield parameters of okra. Plant height, chlorophyll content, yield and yield attributes and biomass yield were highest for VC along with 100% RDF. Significant improvement in soil physical, chemical and biological properties were observed on applying the organic amendments. The highest yield of 23.70 t ha-1 was obtained for T3 (VC @ 25 t ha-1 + 100% N: P2O5:K2O), which was 88 % higher over absolute control and 58 % higher over Package of Practices Recommendations. BC along with 100 % RDF recorded 91.05 and 57.05 % yield improvement over control and PoP. Total N, P, K, Ca, S, Mn, Zn, Cu, and B uptake by plants were also highest for VC along with 100% RDF (T3). The highest Fe uptake was observed in VC along with 75 % RDF (T4). Mg uptake was highest for LMC along with 100% RDF. The different amendments had resulted in decrease in bulk density and increase in water holding capacity, pH, EC, CEC and AEC of postharvest soil. T3 (VC + 100% N: P2O5:K2O) recorded the highest value for available N (393.05 kg ha-1) and dehydrogenase (199.74 μg TPF g-1 soil 24 h-1) activity. Available P2O5 (91.34 kg ha-1) and Fe (246 mg kg-1) were highest for LMC + 100% N: P2O5:K2O (T7). BC + 100% N: P2O5:K2O (T9) recorded the highest values for K (224.82 kg ha-1), Ca (391.67 mg kg-1), Mg (62.00 mg kg-1) and S (20.10 mg kg-1) while Mn (55.74 mg kg-1), Zn (190.50 mg kg-1), Cu (5.33 mg kg-1) and B (0.69 mg kg-1) were highest for BC along with 75% N: P2O5:K2O (T10). Yield parameters viz., total fruit yield, fruit yield per plant and fruit length were on par for the treatments applied with vermicompost along with 100 (T3) and 75 % RDF (T4). B: C ratio was also found to be 2.01 for both the treatments. Application of biochar produced from the weed resulted in very good improvement in the physical and electrochemical properties and secondary and micro nutrient contents of the soil. The nutrient composition of amendments varied with the method of conversion. Hence, it could be concluded that application of L. flava vermicompost @ 25 t ha-1 along with 75 % RDF could be recommended for cultivating okra and could be considered as the economically viable option for utilization of this aquatic weed. Incorporation of L. flava biochar helped in improving the soil physical and chemical attributes. L. flava using different composting strategies using vermicompost, biochar, etc. along with inorganic nutrients can be utilized as effective strategies for disposal of weed and to improve soil health and crop productivity.