Post-Harvest Season Series: Why Soil Biology Matters

Introduction: Harvest Is Not the End of the Season  

As September approaches, many growers are entering an important transition period in the cropping season. Harvest is underway for some crops, while others are approaching maturity. Although attention naturally shifts toward harvesting, field cleanup, and preparing the next crop, an equally important process continues beneath the soil surface.

The crop may be coming out of the field, but the biology of the soil is still at work. After harvest, crop residues and remaining roots become important sources of carbon for soil microorganisms. Beneficial soil bacteria and fungi support organic matter decomposition, nutrient cycling, disease suppression, and the development of healthy soil structure (1). These ongoing biological processes help maintain soil functions that are important for supporting healthy crop growth in the following season.

The post harvest period is not simply a gap between two crops, it is an opportunity to understand and support the biological processes that contribute to healthy, productive, and resilient soils.

So, what happens in the soil after harvest? How do microorganisms contribute to residue decomposition and nutrient cycling? And how can post-harvest management influence soil biological activity?

In this first article of our Post-Harvest Season Series, we take a closer look beneath the soil surface to understand why soil biology matters after harvest and how supporting the soil ecosystem today can help create better conditions for the crop of tomorrow.

Understanding Soil Biology 

Soil is more than a medium for anchoring plants, it is a dynamic ecosystem made up of living organisms and non-living components that interact continuously. It contains bacteria, fungi, archaea, protozoa, nematodes, earthworms, and other organisms, along with organic matter, minerals, water, and air. Together, these organisms interact with plant roots, organic matter, minerals, water, and one another to drive essential soil processes. Soil microorganisms are key contributors to nutrient cycling and organic matter transformation, helping regulate the availability and movement of nutrients within the soil system.

Soil biology refers to both the organisms living in soil and the biological processes they perform. Beneficial microorganisms, particularly bacteria and fungi, play key roles in decomposing organic matter, cycling nutrients, supporting soil structure, and suppressing soil-borne pathogens. Microbial activity also influences nutrient availability and the formation and stabilization of soil aggregates, contributing to overall soil health. Microbial communities are closely linked with soil structure, influencing aggregation and the pore networks that control the movement of water, oxygen, and nutrients.

Importantly, soil biology remains active after harvest. Crop residues and remaining roots provide carbon and nutrients that support microbial communities, allowing decomposition and nutrient cycling to continue between growing seasons. As residues and roots are transformed by soil organisms, some of the resulting organic compounds can become stabilized within soil aggregates, contributing to the formation and persistence of soil organic matter

What Happens Below Ground After Harvest? 

Harvest marks the end of the crop cycle above ground, but biological activity in the soil continues. Remaining roots and crop residues provide carbon and nutrients that support soil microorganisms. Bacteria and fungi colonize and decompose these materials, contributing to the transformation and cycling of carbon and nutrients such as nitrogen and phosphorus.

Image: Soil microorganisms play an important role in decomposing crop residues and driving carbon and nutrient cycling after harvest. 

Source: University of Arizona Cooperative Extension https://extension.arizona.edu/publication/soil-respiration-measuring-how-soils-breathe 

As residues break down, microbial communities and their enzyme activities respond to factors such as residue quality, C:N ratio, soil moisture, temperature, and microbial community composition. Decomposition can temporarily immobilize nutrients, particularly nitrogen, as microorganisms use available nutrients for growth. As decomposition progresses, nutrients are gradually mineralized and returned to soil pools that may become available to subsequent crops. At the same time, microbial processing of plant-derived carbon can contribute to the formation and stabilization of soil organic matter. (2,3)

Residue management can strongly influence these processes. Retaining crop residues generally increases carbon inputs to the soil and can support microbial biomass and activity, while complete removal reduces the amount of organic carbon returned to the soil. A recent global quantitative review of 323 field experiments found that residue harvesting reduced soil organic carbon stocks by an average of 11% in the topsoil, highlighting the important contribution of crop residues to maintaining soil organic carbon. (4) 

However, residue retention does not automatically mean faster nutrient availability. High-carbon, low-nitrogen residues can temporarily cause microbial nitrogen immobilization, as microorganisms use available soil nitrogen while decomposing the material. Over time, as decomposition progresses, nutrients can be mineralized and returned to plant-available pools. Therefore, the type, quantity, and management of residue all influence how effectively post-harvest residues contribute to soil fertility and the next crop. (5)

Organic Matter Formation 

Soil organic matter (SOM) is formed through the continuous transformation of organic carbon entering the soil. Plants are the primary source of this carbon, contributing through root exudates, root turnover, and the deposition of aboveground plant residues. In managed agricultural systems, organic matter inputs are also influenced by crop selection, residue management, harvesting, and the use of organic amendments.

Once these organic inputs enter the soil, microorganisms, particularly bacteria and fungi, play a central role in their decomposition and transformation. Some of the carbon is released as CO₂ through microbial respiration, while another portion is incorporated into microbial biomass and microbial residues. These microbial-derived compounds can subsequently become stabilized in the soil and contribute to longer-term soil organic matter formation (6,7).

Mycorrhizal fungi also contribute to soil carbon dynamics by receiving carbon from plant roots and transferring organic compounds into the soil. Some of this carbon can become protected within soil aggregates or associated with soil minerals, making it less accessible to decomposition and allowing it to remain in the soil for longer periods (8). Soil aggregates can physically protect organic materials, while minerals can bind with organic compounds and help stabilize them.

Therefore, plant inputs, living roots, microbial activity, mycorrhizal associations, and soil structure all work together in the formation and stabilization of soil organic matter. Maintaining regular organic inputs and supporting healthy soil biological activity can help sustain these processes and contribute to long-term soil health.

Image: Soil Organic Matter Formation Processes 

Source: Adapted from Soil organic matter formation, persistence, and functioning: A synthesis of current understanding to inform its conservation and regeneration. M. Francesca Cotrufo and Jocelyn M. Lavallee. 2022.

Why Soil Biology Matters for the Next Crop 

The health of the next crop begins before the next seed is planted. After harvest, soil microorganisms continue to decompose crop residues, cycle nutrients, and transform organic matter. These biological processes regulate nutrient cycling and can contribute to nutrient availability for the following crop while supporting the development of a healthy soil environment.

Active soil biology can also contribute to better soil structure, nutrient cycling, organic matter formation, and root–microbe interactions. Beneficial microorganisms, including bacteria and fungi, interact with plant roots and can support nutrient acquisition and root development. When compatible living host plants are present, mycorrhizal fungi can extend the effective root system and improve access to nutrients and water.

Post-harvest management therefore provides an opportunity to support these natural processes. Returning crop residues, maintaining living roots through cover crops, adding suitable organic materials, and minimizing unnecessary soil disturbance can help maintain microbial activity between cropping seasons.

A biologically active soil does not guarantee higher yields by itself, but it creates a stronger foundation for the next crop. By supporting the organisms responsible for decomposition, nutrient cycling, and soil structure, growers can help maintain soil function and improve the conditions in which the next crop establishes and grows.

Preparing the Biological Foundation for the Next Crop 

The period between harvest and the next crop is an important opportunity to support soil biological activity. Soil microorganisms need carbon, nutrients, moisture, and suitable habitat to remain active. Keeping crop residues in the field, maintaining living roots where possible, and minimizing unnecessary soil disturbance can help provide these resources.

Cover crops are one practical way to maintain biological activity after harvest. Their roots provide a continuing source of carbon to soil microorganisms, while their residues contribute additional organic material to the soil. A meta-analysis of 81 studies found that cover crops increased microbial biomass carbon, microbial biomass nitrogen, and microbial community indicators compared with no cover crop (9). Keeping crop residues in the field and minimizing unnecessary soil disturbance can further help maintain microbial activity and provide a more stable environment for soil organisms. Together, these practices help maintain organic inputs and biological activity between cropping seasons, supporting a healthy biological foundation for the next crop.

These practices do not instantly build soil health, and their effects depend on soil type, climate, crop species, and management. However, maintaining organic inputs, living roots, and a stable soil habitat helps support the microorganisms involved in decomposition, nutrient cycling, and soil organic matter transformation. In this way, post-harvest management can help create a stronger biological foundation for the next crop.

Conclusion

Healthy soils are built through continuous biological activity and balanced management. The post-harvest period provides an opportunity to maintain the organic inputs, living roots, and soil conditions that support microbial communities and the processes they drive.

Practices such as retaining crop residues, maintaining living roots through cover crops, minimizing unnecessary soil disturbance, and using appropriate biological inputs can help sustain soil biological activity between cropping seasons. As part of an integrated soil-management approach, Nurture Growth Biofertilizer can complement these practices by introducing beneficial microorganisms that support the biological processes occurring within the soil. 

Building soil health is a long-term process, and no single practice or input can achieve it alone. By nurturing the biological processes within the soil after harvest, growers can help create a stronger foundation for nutrient availability, root development, and crop establishment in the season ahead.

The next crop begins with the soil you nurture today.

Blogger Biography: 

Dr. Ankita Garkoti is a Senior Science Officer at Nurture Growth Bio Fertilizer. She has over 9 years of experience in Agriculture research and extension. Her areas of specialization encompass Plant Pathology, Microbiology, Plant Protection, Organic farming, Biofertilizers, Organic Fertilizers, and Biocontrol agents.     

She holds a Ph.D. in Plant Pathology and a master's degree in Botany with a specialization in Plant Pathology. Her doctoral research involved an in-depth study of lentil wilt and its management through various practices. She has extensive experience in organizing training programs on Organic and Natural farming techniques for farmers, agricultural growers, students and other stakeholders.  

References:

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Arcand, M. M., Helgason, B. L., & Lemke, R. L. (2016). Microbial crop residue decomposition dynamics in organic and conventionally managed soils. Applied Soil Ecology, 107, 347–359. https://doi.org/10.1016/j.apsoil.2016.07.001

Cotrufo, M. F., Ranalli, M. G., Haddix, M. L., Six, J., & Lugato, E. (2019). Soil carbon storage informed by particulate and mineral-associated organic matter. Nature Geoscience, 12, 989–994. https://doi.org/10.1038/s41561-019-0484-6

Cotrufo, M. F., Soong, J. L., Horton, A. J., Campbell, E. E., Haddix, M. L., Wall, D. H., & Parton, W. J. (2015). Formation of soil organic matter via biochemical and physical pathways of litter mass loss. Nature Geoscience, 8, 776–779. https://doi.org/10.1038/ngeo2520

Kallenbach, C. M., Frey, S. D., & Grandy, A. S. (2016). Direct evidence for microbial-derived soil organic matter formation and its ecophysiological controls. Nature Communications, 7, 13630. https://doi.org/10.1038/ncomms13630

Muhammad, I., Wang, J., Sainju, U. M., Zhang, S., Zhao, F., & Khan, A. (2021). Cover cropping enhances soil microbial biomass and affects microbial community structure: A meta-analysis. Geoderma, 381, 114696. https://doi.org/10.1016/j.geoderma.2020.114696

Rezgui, C., Trinsoutrot-Gattin, I., Benoit, M., Laval, K., & Riah-Anglet, W. (2021). Linking changes in the soil microbial community to C and N dynamics during crop residue decomposition. Journal of Integrative Agriculture, 20(11), 3039–3059. https://doi.org/10.1016/S2095-3119(20)63567-5

Wang, M., Pendall, E., Fang, C., Li, B., & Nie, M. (2018). A global perspective on agroecosystem nitrogen cycles after returning crop residue. Agriculture, Ecosystems & Environment, 266, 49–54. https://doi.org/10.1016/j.agee.2018.07.019

Wang, X., Chi, Y., & Song, S. (2024). Important soil microbiota’s effects on plants and soils: A comprehensive 30-year systematic literature review. Frontiers in Microbiology, 15, 1347745. https://doi.org/10.3389/fmicb.2024.1347745