MSc

The present study on “Biological profile of ferralitic alluvial paddy soils under long term differential fertilizer application” was formulated with the objective of studying the variations in the important biological properties of ferralitic alluvial soils under long term fertilizer experiments with rice-rice cropping sequence and the relationship of these properties with yield and yield attributes. The soils of three long term fertilizer experiments at RARS, Pattambi (listed below) formed the study material 1) Permanent Manurial Trial with tall indica rice variety (PMT- Tall), 2) Permanent Manurial Trial with dwarf indica (PMT- Dwarf), 3) AICRP on long term fertilizer experiments (LTFE).
For (PMT- Tall) the treatment combination T7 which is an integrated nutrient package of 10 kg N ha-1 as green leaf (GL) + 10 kg N ha-1 as cattle manure (CM) + NPK 20:20:20 kg ha-1 significantly and positively influenced most of the soil biological properties like bacteria, fungi, actinomycetes and Azotobacter, levels of soil enzymes urease, phosphatase and dehydrogenase, microbial biomass carbon (MBC), C and N mineralization potential, hot water extractable carbohydrates (HWC) and in turn plant characters like height, no. of tillers and no. of panicles plant-1 and ultimately grain and straw yield. For other characters like population of arthropods, P solubilizers and soil respiration T5 (20 kg N ha-1 as CM + NPK 20:20:20 kg ha-1) and for Azospirillum count T3 (20 kg N ha-1 as CM + 20 kg N ha-1 as GL) registered the maximum values. The same trend in favour of integrated nutrient management was observed for (PMT- Dwarf) also, T7 (22.5 kg N ha-1 as GL + 22.5 kg N ha-1 as CM + NPK @ 45:45:45 kg ha-1) registering significantly the highest values for properties like bacteria, actinomycetes, Azotobacter, soil enzymes, MBC, HWC, plant height, no.of tillers, no. of panicles plant-1 and grain yield. For characters like fungi, Azosprillum population and respiratory activity T6 (45 kg N ha-1 as GM+ NPK @ 45:45:45 kg ha-1) was the most effective as was T5 (45 kg N ha-1 as CM + NPK @ 45:45:45 kg ha-1) for P solubilizers and straw yield, T3 (45 kg N ha-1 as CM + 45 kg N ha-1 as GM) for arthropod count and N mineralization and T1 (90 kg N ha-1 as CM) for C mineralisation
In LTFE T8, also an integrated nutrient package {100 percent NPK + FYM @ 5 t ha-1 (to Kharif crop only)} produced significantly the higher populations of earthworms, arthropods, bacteria, actinomycetes, fungi, Azospirillum, Azotobacter, soil enzymes, MBC, HWC, C and N minerlisation potential, no. of panicles and in turn grain yield. Only for a very few characters the other treatments had any effect like T10 {100 percent NPK + in situ growing of Sesbania aculeata (for Kharif crop only)} for straw yield and no. of tillers and T3 (150 percent NPK) for p solubilizers.
In nutshell for sustenance of soil health and maximum yield, treatment T7 (10 kg N ha-1 as GL+ 10 kg N ha-1 as CM + NPK @ 20:20:20 kg ha-1) can be adjudged to be the best for (PMT- Tall). For (PMT- Dwarfl), T7 (22.5 kg N ha-1 as GL + 22.5 kg N ha-1 as CM + NPK @ 45:45:45 kg ha-1) was the best treatment and T8 {100 per cent NPK + FYM @ 5 t ha-1 (to Kharif crop only)} for LTFE.