Browsing by Author "Shiv Prasad, T"

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    Soil phosphorus dynamics and its interactions in red sandy loam soils
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture, Padannakkad, 2025-06-19) Shiv Prasad, T; Nideesh, P
    The study entitled “Soil phosphorus dynamics and its interactions in red sandy loam soils” was carried out at the instructional farm II, College of Agriculture, Padannakkad, to assess the short-term dynamics of phosphorus in the sandy loam soils cultivated with cowpea as modified by different amendments and to study its impact on growth and yield parameters of cowpea. The study was carried out in two parts; an incubation experiment and a field experiment. Soil samples collected from the instructional farm II were incubated at field capacity for three months, and analysis was done after the incubation period. Treatment combinations were T1 (Control), T2 (Soil test-based P fertilizer), T3 (T2 + ZnSO4 @ 20 kg ha-1), T4 (T2 + Borax @ 10 kg ha-1), and T5 (T2 + Lime @ 250 kg ha-1). Analysis of the soil samples before incubation experiment showed that the soil is very strongly acidic, non saline and high in organic carbon. Soil sample analysis after incubation showed a significant effect of lime application on the soil pH. Available P was also significantly affected by treatments and was highest in T4 (T2 + borax) and T5 (T2 + lime) treatments. Treatments have significant effect on the Phosphorus activity coefficient (PAC) also having higher values of 15.82% and 15.79% in T4 and T5 treatments respectively, indicating better conversion of total P to available P in those treatments. On analysing the different P pools, Ca-P and Fe-P pools were found at significantly higher levels in treatment T5 (T2 + lime), whereas the Al-P, loosely bound P, and reductant P were significantly higher in T4 (T2+ borax). The incubation study revealed that boron and lime application could help in enhancing the available P content in the soil. The application of borax has a significant effect on the soil P pools also indicating its role in enhancing the reserve soil P pools. The field experiment was laid out in a randomized block design with eight treatments and three replications. The treatment combinations were T1 (KAU POP based lime and fertilizers), T2 (Soil test-based fertilizers and lime), T3 (KAU organic POP ), T4 (T2 + ZnSO4 @ 20kg ha-1), T5 (T2 + Borax @ 10 kg ha-1), T6 (T2 + PSB), T7 (T3 + PSB) and T8 (T2 excluding P + Nano P @ 10ml L-1). The cowpea variety Kanakamony was used as a test crop for the field experiment. Results of the field experiment showed significant changes in the soil chemical properties and phosphorus pools. At flowering, T3 ( KAU organic POP) treatment showed significantly higher soil pH which was on par with T1 (KAU POP) treatment. Phosphorus pools were significantly affected by treatments. Available P content was significantly higher in T1 (KAU POP) and T2 (KAU organic POP) treatments, Fe bound P and Al bound P were significantly higher in T4 ( T2 + ZnSO4) treatment. Ca bound P and reductant P were significantly higher in T2 (Soil test-based fertilizer and lime) and T3 (KAU organic POP) treatments respectively. Loosely bound P was significantly higher in T1 (KAU POP) and Organic P content was higher in T3 (KAU organic POP) treatment. Total P was significantly higher in T7 (T3 + KAU organic POP) treatment. At post-harvest, there was no significant change in the soil pH, EC and OC. Available P was significantly higher in T1 (KAU POP) treatment which was on par with T2, T3 and T4 treatments. Fe bound P and Al bound P were significantly higher in T4 (T2 + ZnSO4) treatment, whereas Ca bound P and Reductant P were significantly higher in T3 (KAU organic POP) treatment. Organic P was significantly higher in T1 (KAU POP) and T3 (KAU organic POP) treatments. Loosely bound P was significantly higher in T7 ( T3 + KAU organic POP) and total P was highest in T3 and T7 treatments. Treatment T2 (soil test based fertilizer and lime) had significantly higher PAC (Phosphorus activation coefficient) values at flowering and post-harvest stages (14.977 and 11.443% respectively) than the other treatments. The plant analysis results revealed that higher N and P were recorded in treatment T8 and K content was highest in treatment T1. Total Ca, Mg and Fe were highest in treatment T2. Total S was highest in treatments T1 and T7. Total Cu and Mn were highest in treatment T3. Total Zn was highest in T4 and T7 treatments, whereas B was highest in T5. Application of amendments had no significant effect on the growth parameters of cowpea, while yield parameters like pod weight per plant, pod yield and grain weight were significantly affected by treatments. Pod weight per plant was highest in T3, T7 and T8 treatments while pod yield was maximum in T8. Grain yield was significantly higher in T7 and T8 treatments compared to other treatments. The study results revealed a change in the dynamics of phosphorus pools and soil properties with the application of different amendments. Application of lime helps in increasing available P in the soil. The synergistic and antagonistic behaviour of added amendments such as B and Zn were also seen affecting different pools and hence the available P. Even though the available P is very high in the coastal sandy soils, a small amount of fertilizer addition is necessary to ensure the sustainable release of phosphorus from the reserve pools, as is evident from the PAC values. The addition of amendments such as Borax, ZnSO4, etc., could help in fixing excess P in the soil and can thus reduce the negative impact on the environment and soil. Borax can also help in the sustainable release of fixed P from the reserve pools. Foliar application of nano P fertilizer (DAP) was found to increase the yield parameters and is an alternate option for ensuring P supply to plants without adding P to the soils.