Short‐Term Impact of Organic Fertilization and Seasonal Variations on Enzymes and Microbial Indices Under Rice–Wheat Rotation

Abstract

The impact of organic fertilization (OF) and seasonal variation on microbial indices was compared with chemical fertilization (CF) and integrated nutrient management (INM) practices under rice–wheat sequence. The field experiments conducted from 2011 to 2013, adopting a split‐plot design, showed that CF practices decreased the soil pH, microbial biomass carbon, and CO2 metabolic quotient but increased the percentage of microbial biomass C to soil organic carbon. Organic fertilization though enhanced the soil organic carbon but resulted in variable microbial responses. Under paddy soil, OF practices registered an increase in dehydrogenase, alkaline phosphatase (ALK), and fluorescein diacetate activity by 35, 169, and 22% in the first, second, and third crop cycle, respectively, compared with CF. However, the ratios of ALK and aryl sulfatase to microbial biomass carbon were higher (0.378 and 0.498, respectively) in INM‐practiced paddy soil compared to 0.364 and 0.447 in OF. Relatively higher soil enzymatic activity titers, basal respiration, microbial biomass carbon in winter wheat compared to summer paddy, indicated a more pronounced effect of season on soil microbial attributes than soil management practices. Though, organic manure could improve the soil quality in tropical agro‐ecosystems, compared to CF but their biannual application was not microbiologically beneficial beyond three rice–wheat crop cycles.

Evaluation of soil health in organicvs. conventional farming of basmati rice in North India

“…). Others have also reported enhanced soil biochemical activity in a single growing season ( Arancon et al, ; Dinesh et al., ; Lazcano et al, ; Gaind et al, ) in response to short‐term incorporation of organic manures and biofertilizers. This indicates that instantaneous increases in soil enzyme activities were associated with a rapid increase of organic substrates required for microbial metabolism.…”

“…As observed in other studies, long‐term application of organic amendments has also exerted a considerable influence on the activities of soil enzymes in our study, in which enzyme activities were 28 to 42% higher (Tab. ) in organic systems than in their conventional counterparts ( Singh et al, ; Gaind et al, ; García‐Orenes et al, ). Plenty of microbial substrates (C and nutrients) in composts can facilitate microbial population build up ( Witter and Kanal , ) and further stimulate them to produce enzymes responsible for the conversion of unavailable to an available form of nutrients ( Yadav et al, ).…”

“…Despite this understanding, mixed reports have been documented on the impact of organic manure application on soil microbial biota with studies showing stimulation of soil microbial activity (Hansen et al, 2001;Shannon et al, 2002;Quintern et al, 2006;Mandal et al, 2007;Chaparro et al, 2012) and others showing negligible or no influence on microbial indices (Treseder, 2008). In this regard, accumulation of recalcitrant (or stable) humified C has been attributed to declining biological health over time in the organically amended soil (Gaind and Singh, 2016). Additionally, several authors have suggested that soil biota may serve as a better (or more sensitive) indicator of management practices than non-living indicators of soil fertility.…”

A review on effective soil health bio-indicators for ecosystem restoration and sustainability

“…A recent study indicated that agricultural intensifications could alter the expressions of soil biochemical indicators (e.g., enzyme activity) quicker than soil microbial diversity indicators (Pérez-Brandán et al, 2016 ). To that end, soil enzyme activities are often used as effective indicators for assessing the environmental consequences of applications of agricultural chemicals for soil nutrition (Gaind and Singh, 2016 ; Sihi et al, 2017 ) and xenobiotic pesticides (Sahoo et al, 2016 ; Mahapatra et al, 2017 ). One can also evaluate the ecological consequences (e.g., soil carbon loss) of land use management intensities, along with a wide spatial gradient of edaphic factors, using microbial ecophysiological traits, including growth efficiency, qCO 2 , and indicator proteins (Malik et al, 2018 ).…”

Influence of novel microbial formulations on enzymes and microbial indices of soil during wheat cultivation

“…This was in accordance with who reported higher DHA values in soils amended with compost and humic acid as compared to soil fertilized with chemical fertilizers. Chemical fertilizers may also promote the growth of microbial communities as compared to control by countering the limitation of mineral nutrients (Gaind and Singh 2016).…”