MSc

The investigation entitled “Boron nutrition of wet land rice (Oryza sativa L.)” was conducted at Cropping Systems Research Centre, Karamana, during 2015-2016 with medium duration rice variety Uma, to assess the optimum dose and methods of application of boron to be recommended for wet land rice in the acid soils of Kerala.
The experiment was laid out in a randomized block design with three replications and nine treatments. The treatments consisted of four levels of soil application of boron (B) viz., T1- 0.25 kg B ha-1, T2- 0.50 kg B ha-1, T3- 0.75 kg B ha-1 and T4- 1.0 kg B ha-1 and four levels of foliar spray viz., T5- 250 ppm B, T6- 500 ppm B, T7- 750 ppm B and T8- 1000 ppm B in addition to a no boron control (T9). The B treatments were applied in two equal splits at active tillering and flowering stages. All treatments were provided with manures and fertilizers as per the KAU POP.
The initial analysis of the soil of the experimental site revealed that the soil was strongly acid in reaction with normal EC and sandy clay in texture. The soil was low in CEC, high in organic carbon, medium in the available status of N and K, high in P, Ca, Mg and S, sufficient in Cu and Zn and deficient in B (0.5 ppm). Results revealed that among the soil treatments, T4 recorded minimum spikelet sterility (16.33 %) and maximum percentage of filled grains (83.67 %). It also recorded higher values for panicle weight (2.71 g) and thousand grain weight (24.48 g) which resulted in producing the highest grain (5502.85 kg ha-1) and straw (7014.52 kg ha-1) yields. The maximum B content of index leaf at active tillering and panicle initiation stages were recorded by T4 and that at flowering stage was recorded by T3. Uptake of N, K, Ca and B by straw and that of K, Cu, Zn and B by grain were found to be higher in T4. Lower values for percentage disease incidence and phenol contents were also observed in T4. All soil treatments significantly increased the availability of Zn and B. The treatment T3 receiving 0.75 kg ha-1 B as soil application was found to be statistically on par with T4.
Among the graded levels of foliar treatments ranging from 250 to 1000 ppm, it was found that 250 ppm B (T5) was superior to higher levels with respect to biometric observations, yield and yield attributes, B content of index leaf, nutrient uptake and phenol content.
The number of total and productive tillers, panicle length, number spikelets per panicle, scoring of leaf folder attack, cost of cultivation, seed germination, uptake of P, Mg, Cu and Zn by straw and that of Mg by grain, soil pH and EC and availability of N, P, K, Ca, Mg and Cu were found non-significant by the treatments.
Soil treatments gave significantly higher grain yields compared to foliar treatments. Economic analysis revealed the superiority of B treatments over control. The highest gross and net returns and B:C ratio was recorded for the soil treatment T4 (1.52) which was on par with T3 (1.48).
Since the yield and B:C ratios for T4 and T3 were on par, in the case of micronutrient recommendations, it is mandatory to recommend the lower dose i.e., 0.75 kg B ha-1 as soil application in two splits at active tillering and flowering stages to meet the B requirement of wet land rice in the acid soils of Kerala.