To increase crop productivity, modern agricultural practices
comprise fertilisers, algaecides, herbicides and fungicides. Fertiliser
application profoundly impacts soil microbes and enzymes, with organic
fertilisers generally promoting beneficial microbial communities and enzyme
activities like phosphatase and dehydrogenase, while high-dose inorganic
fertilisers can lead to negative effects, such as reduced microbial richness
and inhibition of certain enzyme activities, often altering soil nutrient
availability and pH. Long-term studies show that organic amendments can enhance
microbial biomass and functional diversity, supporting nutrient cycling, while
mineral fertilisers, especially in excess, may negatively affect soil health
and microbial respiration. Fungicide application negatively impacts soil health
by reducing microbial biomass, decreasing fungal populations, altering
microbial community structure, and inhibiting enzyme activities, such as
phosphatases, dehydrogenases, and ureases. These effects disrupt soil fertility
and ecological functions, although the specific impact depends on the
fungicide's type, dose, persistence, and soil conditions. Algicide application
can negatively impact soil microbes and enzyme activities, decreasing microbial
populations and altering community structure due to toxicity, while
simultaneously affecting key enzymes like urease, phosphatase, and catalase
involved in nutrient cycling and organic matter breakdown. However, studies
show a complex relationship, with algicides sometimes causing an initial
increase in certain microbial populations before a decline, highlighting the
importance of application rates and exposure time. The overall effect can lead
to reduced soil fertility and long-term ecological consequences. Herbicide
application generally alters soil microbial communities and enzyme activities,
often with an initial inhibitory effect on microbial respiration and enzyme
activity, though this can be temporary. The specific impact varies
significantly based on the herbicide's type, dose, and soil conditions. Some
herbicides can be particularly detrimental to beneficial microbes, slowing
crucial processes like nitrogen cycling, while others may promote the growth of
specific microbes involved in herbicide breakdown. Combined herbicide
applications often intensify negative effects, and long-term exposure can shift
microbial community composition and function, influencing soil health and
fertility.
The purpose of this study was to evaluate the effects of
soil microbial population and soil enzyme activity by the use of fertiliser in
maize and inorganic input in the rice ecosystem.
A field experiment (2021 to 2023) was carried out using
synthetic fertiliser doses with maize crops, followed by rice crops using
inorganic inputs. Soil microbial population and enzyme activities were
examined.
Maize field experiment revealed that the plots treated with
75 % Standardised Dose of Fertiliser (SDF) of NPK had the highest populations
of diazotrophs (124 × 105cfu / g), Phosphobacteria (66.33 × 105cfu / g), and
Azospirillum (0.409 × 105 MPN / g) than 100 % and 150 % SDF of NPK. The soil
enzyme activity was higher in the unfertilized control plot than fertilised
plot. These experimental results revealed that a low amount of fertiliser and
no fertiliser favour the growth of soil microorganisms and soil enzyme
activities, respectively. Followed by the rice field experiment, revealed that
the soil microbial population was decreased by the application of inorganic
inputs viz., fertiliser, algaecide, herbicide and fungicide. However, the
maximum soil microbial population was found in algaecide application, followed
by herbicide and fungicide.
The field experiment concluded that soil microbial
population and enzyme activity were affected by inorganic amendments. Less
inorganic fertilisers and no fertilisers improve soil microbial activities and
soil enzyme activities.
Author(s) Details
M. Jeya Bharathi
Department of Agricultural Microbiology, Agricultural College and Research
Institute, Tamil Nadu Agricultural University, Madurai 625104, Tamil Nadu,
India.
Mariyappillai
Anbarasu
School of Agriculture, Vels Institute of Science, Technology and Advanced
Studies (VISTAS), Pallavaram -600117, Chennai, Tamil Nadu, India.
R. Raghu
Department of Biotechnology, Centre for Plant Molecular Biology and
Biotechnology, Tamil Nadu Agricultural University, Coimbatore 641003, Tamil
Nadu, India.
E. Subramanian
Krishi Vigyan Kendra, Agricultural College and Research Institute, Tamil
Nadu Agricultural University, Madurai 625 104, Tamil Nadu, India.
Please see the book here :- https://doi.org/10.9734/bpi/mbrao/v5/6350
