Soil Phosphorus Dynamics as Influenced by Chemical Fertilizers and Vermicompost under Pea (Pisum sativum var. hortense) Cultivation
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Date
2021
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Department of Soil Science and Agricultural Chemistry, BAU, Sabour
Abstract
Phosphorus is a vital element for plant and animal nutrition. It is one of the important limiting nutrients for crop production in many agricultural areas. Despite its importance, only a small proportion (~ 0.1-1.0 %) of it is available for plants. Based on soil testing reports of 38.5 million samples, 42 % of Indian soil samples were found deficient in available phosphorus. For the farming system to remain productive, and to be sustainable in the long term, it is necessary to replenish the reserves of nutrients that are removed or lost from the soil, which is possible by the application of renewable agricultural resources at a large scale. Influence of organics on dynamics of phosphorus is required to studied to improve P availability to the crops.
Vermicompost is one of those organic sources of plant nutrient having potential to maximize the benefits from the legume-Rhizobium system by increasing organic matter content in soils. The quality of vermicompost, mainly its phosphorus (P) content might be upgraded by introducing some minerals like rock phosphate (RP) and phosphate along with solubilizing bacteria in the substrate during the vermicomposting. This enrichment technique of vermicomposting has potential to popularize vermicompost among farming community. But only less information is available on the effect of enriched vermicompost on growth, nodulation, dry matter accumulation and yield of garden pea. Information related to the influence of enriched vermicompost on P transformation and other chemical as well as biological properties of soil is also very scanty. Thus, there is a need to study the effect of enriched vermicompost on fertility of soil and productivity of the crops for achieving sustainability in agriculture.
In the view of above facts, the present investigation “Soil Phosphorus Dynamics as Influenced by Chemical Fertilizers and Vermicompost under Pea (Pisum sativum var. hortense) Cultivation” was carried out with four objectives:1) To find out the effect of chemical fertilizers and vermicompost on phosphorus release pattern under incubation study. 2) To study the influence of chemical fertilizers and vermicompost on growth, yield and uptake by garden pea (Pisum sativum var. hortense) crop. 3) To assess the effect of chemical fertilizers and vermicompost on soil phosphorus transformation under garden pea (Pisum sativum var. hortense) crop and 4) To estimate the impact of chemical fertilizers and vermicompost, on soil microbial dynamics specially Rhizobium, PSB, and Azotobacter population.
One incubation study was carried out in a completely randomized design with 13 treatments and three replications to examine the effect of P sources on the transformation of phosphorus at different intervals. Details of treatments are as under:
T1 (N0: P0: K0), T2 (N40: P0:K50), T3 (N40: P30:K50), T4 (N40: P45:K50), T5 (N40: P60:K50), T6 (50 % RDP through VC), T7 (50 % RDP through SSP + 50 % RDP through VC), T8 (75 % RDP through SSP + 25 % RDP through VC), T9 (50 % RDP through EVC), T10 (50 % RDP through SSP +50 % RDP through EVC), T11 (75 % RDP through SSP +25 % RDP through EVC), T12 (100 % RDP through VC), T13 (100 % RDP through EVC).
Four sets of the experiment were established for incubation study and each set was used for phosphorus dynamics study at 0, 30, 60, and 90 days after incubation (DAI) respectively. Phosphorus transformation was also studied under field conditions with these treatments to study the effect of vermicompost on productivity of garden pea.
It is evident from the results of incubation study that labile-P, Fe- Al-P and Ca-P content of experimental soil treated with vermicompost increased up to 60 DAI and decreases then after. However, content of these fractions in soil treated with fertilizer increased only up to 30 DAI. The highest contents of labile P were recorded when soil was treated with T10 (50 % RDP through SSP + 50 % RDP through EVC), however, the highest Fe-Al-P and Ca-P fraction were recorded in the soil treated with enriched vermicompost alone. The percentage increase in labile P, Fe-Al-P and Ca-P in enriched vermicompost treated soil over fertilizer treated soil at 90 DAI were 11.03, 18.36 and 2.78 percent respectively. Similar trend of P transformation was observed under field conditions. It was probably due to augmenting effect of enriched vermicompost on availability of phosphorus in soil. Residual-P content of experimental soil was not affected significantly by the treatments.
Application of 50 % RDP through SSP + 50 % RDP through EVC resulted the highest plant height, root length, nodule count, nodule dry weight, dry matter accumulation, yield attributes, pod yield and uptake of N, P and K by the crop. Application of 50 % RDP through chemical P and 50 % RDP through enriched vermicompost resulted in higher green pod yield (93.42 q ha-1) of garden pea which was 12.81 % higher than that recorded with RDF.
The highest increase in available N, available P2O5 and K2O was recorded in soil treated with T10 (50 % RDP through SSP + 50 % RDP through EVC), however, SMBC, acid phosphatase, alkaline phosphatase and microbial count (Rhizobium, Azotobacter and PSB) were found to be the highest in soil treated with enriched vermicompost alone.
Based on experimental finding it can be concluded that to achieve the highest yield of garden pea 50 % RDP should be supplied through enriched vermicompost and 50% through chemical fertilizers, however, to increase microbial population, acid phosphatase and alkaline phosphatase activity in soil 100 % RDP should be supplied through enriched vermicompost. Enriched vermicompost was found superior to normal vermicompost and chemical fertilizer for increasing labile P pool in soil. Enriched vermicompost was found superior to normal vermicompost in increasing soil microbial biomass carbon, population of Rhizobium, Azotobacter and PSB and activities of acid phosphatase (AcP) and alkaline phosphatase (AlP). SMBC, count of Rhizobium, Azotobacter and PSB, AcP and AlP in enriched vermicompost treated soil were found to be 18.18, 6. 67, 9.17, 12.88, and 2 percent higher respectively over that recorded in normal vermicompost treated soil.