Role of soil microbes in sustainable crop production and soil health: A review

K.K. Shah1*, S. Tripathi2, I. Tiwari2, J. Shrestha3, B. Modi4, N. Paudel5,6, B.D. Das7

1Institute of Agriculture and Animal Science, Gokuleshwor College, Tribhuvan University, Nepal
2Himalayan College of Agricultural Science and Technology, Purbanchal University, Kathmandu, Nepal
3Nepal Agricultural Research Council, National Plant Breeding and Genetics Research Centre, Khumaltar, Lalitpur, Nepal
4Central Department of Chemistry, Tribhuvan University, Kathmandu, Nepal
5National Institute of Horticultural and Herbal Science, Rural Development Administration, 55365 Wanju, Republic of Korea
6Department of Applied Plant Science, Kangwon National University, 24341 Chuncheon, Republic of Korea
7Department of Botany, Mahendra Morang Adarsh Multiple Campus, Biratnagar, Tribhuvan University, Nepal

(Manuscript received 12 August 2020; accepted for publication 29 March 2021)

Abstract. Global food production needs to be increased in order to feed the world’s growing population and at the same time, the reliance on inorganic fertilizers and pesticides should be minimized. To accomplish this goal, the various beneficial associations between plants and soil microorganisms should be explored. The soil microbes are bacteria, actinomycetes, viruses, fungi, nematode, and protozoa. They have an important soil function that has fulfilled several useful tasks in the soil system. Microbes support biological nitrogen fixation of different biological transformations that support the accumulation and utilization of key nutrients, support root and shoot growth processes, disease control, and improve soil quality in crop cultivation. Soil microbes offer nutrient-dense nourishment improved crop production and recycle soil solutions. They play an essential role in decomposing organic matter, cycling nutrients, and fertilizing the soil. Besides, they improve plant growth on various physiological parameters of plants by a number of mechanisms. The mechanism involved in growth promotion includes plant growth regulators, production of different metabolites, and conversion of atmospheric nitrogen into ammonia in direct and indirect ways. In addition, soil microbes offer resistance against diseases. This review outlines the significant impact of soil microbes on sustainable agricultural growth, the benefits of microbes in maintaining soil health, and their interactions.

Bulk density and organic carbon contents of soil pedons influenced by different tree species

C.M. Ahukaemere1, D.N. Osujieke2, V.O. Ugwa1, A.O. Ogwuche1

1Department of Soil Science and Technology, Federal University of Technology, PMB 1526 Owerri, Imo State, Nigeria
2Department of Soil Science and Land Resources Management, Federal University Wukari, PMB 1020 Wukari, Taraba State, Nigeria

(Manuscript received 1 November 2018; accepted for publication 24 March 2019)

Abstract. Bulk density and organic matter content of soil are important soil attributes used in predicting the productivity potentials of soil and overall soil quality. The distribution of soils bulk density and organic carbon in horizons of soil pedons under different three tree species (Hevea brasiliensis – rubber, Pentaclethra macrophylla – oil bean and Irvingia gabonensis – ogbono) in Owerri, Southeastern Nigeria were investigated. A random survey method was used in field sampling. In all, three profile pits were dug, one in each site. A total of 36 soil samples were collected and analyzed for the study. Samples were collected at different horizon levels (A, AB, Bt1 and Bt2). Three representative samples were collected from each horizon. Bulk density, organic carbon and other routine analyses were performed using routine laboratory techniques. Mean, coefficient of variation and correlation analyses were analyzed. From the results obtained bulk density increased with depth, ranging from 1.05-1.81 g cm-3 in the rubber plantation, 1.02-1.70 g cm-3 in ogbono plantation and 1.11-1.57 g cm-3 in oil bean plantation. Bulk density decreased with the increase the organic carbon content. However, mean bulk density values irrespective of tree species did not exceed critical limits ranging from 1.28 to 1.32 g cm-3 as appropriate. Organic carbon ranged from 0.06-0.89 g kg-1 in rubber plantation, 0.42-0.87 g kg-1 in ogbono plantation and 0.72-1.25 g kg-1 in oil bean plantation. The epipedal horizons contained higher organic carbon than the endo-pedal horizons. The average organic carbon contents of the pedons were lower than the critical value irrespective of the tree species. The oil bean plantation had higher organic carbon and total nitrogen than the ogbono and rubber plantation while the ogbono plantation contained higher available phosphorus than the other two plantations studied.