MSc

A study on “Effect of soil amelioration and supplementary foliar nutrition on rice yield in Kuttanad” was carried out to evaluate the effect of soil amelioration with rice husk ash in abating iron toxicity and supplementary foliar application of a customized nutrient formulation in increasing rice yield in the low lands of Kuttanad. The overall fertility status of this region indicated that the soil was acidic with high level of P, medium level of available N and K and wide spread deficiency of Ca, Mg, Cu, Zn and B.
A customized nutrient formulation with a composition of K (8.9%), Mg (3.2%), Ca (3.7%), Zn (2.1%), Mn (0.23%), B (3.5%) and Cu (0.96%) was developed based on the available nutrient status of the region and crop requirement. This formulation was used for supplementary foliar nutrition @ 5 kg ha-1 as foliar application of 0.5% solution in two splits at maximum tillering and panicle initiation stage.The field experiment was conducted at Rice Research Station, Moncompu (July to November 2017) with nine treatments and the treatments were T1(Recommended dose of fertilizer and lime (RDF) ),T2 (Soil test based RDF and lime (based on pH)),T3 (Soil test based RDF + Rice husk ash(RHA) @ lime in T2),T4 (Soil test based RDF + RHA @ ½ lime in T2),T5 (T1 + foliar spray of 0.5% solution of customized formulation at tillering and panicle initiation stage (FS) ),T6 (T2 + FS),T7 (T3 + FS),T8 (T4 + FS) and T9(50% Soil test based RDF + RHA @ lime in T2 + FS) replicated thrice in RBD using rice variety Uma.
Growth and yield of rice increased significantly due to soil amelioration and supplementary foliar nutrition. During the maximum tillering stage, the highest plant height (55.32 cm) was recorded in the treatment T5 and was on par with all other treatments except treatment T9. The treatments did not show a significant influence on number of tillers at maximum tillering and panicle initiation stages. Treatment T7 recorded the highest number of productive tillers (12.36), which was on par with treatments T6, T5, and T3.
The treatment T7 recorded the highest value for all the yield attributes and yield such as panicles per m2 (549.62), thousand grain weight (26.6 g), number of filled grains per panicle (136.5), grain yield (6.60 t ha-1) and straw yield (8.34 t ha-1). The highest number of panicles per m2 recorded for the treatment T7 was found to be on par with treatments T5 and T6 while for the thousand grain weight the treatment T7 was on par with treatment T6, T8 and T4. For grain yield treatment T7 was found to be on par with all other treatments except treatment T4 and T9.
The results of scoring of iron toxicity using standard evaluation system for rice (IRRI,1996) at maximum tillering stage and panicle initiation stage revealed that during maximum tillering stage, there was no visual symptom on the plants, but during panicle initiation stage, the symptoms were expressed in treatments T1 and T9 and T9 recorded the highest score(3).
Soil analysis done at the time of harvest showed that the pH increased from the initial value of 4.35 to the highest value of 5.5 which was recorded for the treatment T7 and was on par with treatments T3,T4,T5,T8 and T9,while the treatments did not have a significant influence on the EC. The treatment T7 recorded the highest organic carbon content (3.06 %). In the case of primary nutrients, for both available N and P treatment T8 recorded the highest value (385.76 kg ha-1 and 25.22 kg ha-1) and for available K (218.4 kg ha-1) it was recorded by treatment T7. For exchangeable Ca and Mg the highest value was recorded for treatment T6 (157.33 mg kg-1) and T 7 (29.86 mg kg-1) respectively which was superior to all other treatments. In the case of available S, the treatment T5 recorded the highest value (21.17 mg kg-1).The results showed that the treatment T7 recorded the lowest available Fe (322.5 mg kg-1) and Mn (3.27 mg kg-1) content during the harvest stage. For available Zn, Cu, B and Si, the treatment T7 recorded the highest value (3.01, 2.73, 0.504 and 36.83 mg kg-1 respectively) and was superior to all the treatments except for Zn where the treatments did not have a significant influence.
The results of the plant analysis revealed that the treatment T7 recorded the lowest leaf iron content during the maximum tillering and panicle initiation stage (125 and 141 mg kg-1).In the case of primary nutrients, for N and K content in
grain (1.30 and 0.666 %) and straw (0.77 and 2.32 %) the treatment T7 recorded the highest value and the treatment T8 recorded the highest P content in grain (0.196 %) and straw (0.146 %). In the case of Ca, the treatment T6 recorded the highest value for grain and straw (0.38 and 0.64 %), while for Mg (0.114 and 0.346 %), S (0.351 and 0.373 %) and for Si (0.81and 3.98%) the treatment T7 recorded the highest grain and straw content. Treatment T7 recorded the highest micronutrient content in grain and straw for Mn (42.9 and 157.7 mg kg-1), Cu (6.0 and14.2 mg kg-1), Zn (29.3 and 58.4 mg kg-1) and B (12.1 and16.4 mg kg-1) but recorded the lowest value for Fe content in grain and straw (65 and 154.3 mg kg-1) which indicated the influence of rice husk ash in reducing the iron absorption in plant. The treatment T7 recorded the highest value for uptake of all the nutrients expect for Fe uptake in the plant.
The study revealed that the treatment T7 recorded the lowest percentage of incidence of leaf roller (4.37) and there was no incidence of major diseases during the crop period. Treatment T7 recorded the highest net income (Rs. 87679/-) and BC ratio (1.82).
From the investigation it can be concluded that, treatment T7 (Soil test based RDF + Rice husk ash @ lime (based on pH) + foliar spray of 0.5% solution of customized formulation at tillering and panicle initiation stage) was the best treatment in which the yield increased by 21 per cent compared to RDF and B:C ratio increased from 1.44 to 1.82 . Effect of rice husk ash in ameliorating soil acidity was found to be on par with application of lime based on pH. Use of rice husk ash as soil ameliorant along with soil test based RDF and supplementary foliar nutrition improved rice yield in Kuttanad and reduced the nutritional constraints due to iron toxicity.