Organic Residue Mulching Enhances Soil Biological Activity and Hydrothermal Regime, Improving Water Productivity and Ginger (Zingiber officinale Roscoe) Yield in Sub-Mountainous Northwestern India

In the quiet, rolling foothills of northwestern India, where the land is thin and the rain can be unpredictable, farmers face a constant challenge: keeping the soil alive and the crops fed. For a crop like ginger, which grows its valuable, knotty roots just beneath the surface, the conditions of the earth are everything. The plant is shallow-rooted and sensitive; it needs the soil to stay moist without getting waterlogged, cool without getting too cold, and rich with the tiny, invisible life that helps release nutrients. When the soil dries out or heats up too much, the ginger stops growing, and the harvest shrinks. For decades, farmers have known that covering the ground with a layer of organic material—like dried leaves or stalks—can help hold in moisture and keep the temperature steady. This practice, known as mulching, acts like a blanket for the earth, but scientists have long wondered exactly how different types of this "blanket" affect the hidden world of soil microbes and, ultimately, the farmer's profit.

A team of researchers from Punjab Agricultural University set out to answer these questions in the Kandi region, a sub-mountainous area known for its fragile soils and reliance on agroforestry. Over three growing seasons, from 2021 to 2023, they tested whether covering ginger plants with different kinds of agricultural waste could improve the health of the soil and the yield of the crop. They compared three specific types of mulch: crushed sugarcane waste, paddy straw from rice fields, and wheat straw, against a control group where the soil was left bare. The goal was not just to see if the ginger grew bigger, but to understand the chain reaction that starts with the soil itself. They wanted to know if the mulch could wake up the soil's biological activity, regulate the water and temperature, and make the entire system more efficient with the water it uses.

The results of the study revealed a clear winner among the materials tested. The plots covered with sugarcane trash, applied at a rate of 7.5 tons per hectare, produced the most dramatic improvements. These plots saw the ginger plants grow taller and develop more leaves and stems than any other group. The plants were healthier, with greener leaves that captured more sunlight, and they produced significantly more rhizomes—the edible part of the ginger. In terms of the final harvest, the sugarcane mulch plots yielded 278 quintals per hectare, a massive increase compared to the bare soil plots, which produced only 160 quintals. The ginger grown under the sugarcane cover was also larger and more uniform, with a higher percentage of the big, marketable roots that fetch the best price.

What made the sugarcane mulch so effective was its ability to transform the environment right at the soil's surface. The researchers found that this specific mulch created a stable microclimate. It kept the soil cooler during the hot days and prevented the water from evaporating too quickly, meaning the plants needed far less irrigation. In fact, the sugarcane-mulched plots required 37.5 percent less water than the bare plots to produce their harvest. This conservation of water was not just about saving a resource; it was about efficiency. Because the plants had a steady supply of moisture and a comfortable temperature, they used every drop of water they received to build more biomass and yield. The study calculated that for every cubic meter of irrigation water used, the sugarcane mulch plots produced 7.55 kilograms of fresh ginger, whereas the bare soil plots produced less than three kilograms.

Beyond the physical conditions, the mulch also sparked a revival in the soil's biological life. The researchers measured the activity of the microscopic organisms living in the dirt, looking at how much carbon they held, how much they breathed out, and how active their enzymes were. In the plots with sugarcane mulch, these biological indicators were the highest of all. The soil was teeming with more active life, which helps break down organic matter and release nutrients for the plants to eat. This biological boost was closely tied to the physical benefits; the moist, cool environment created by the mulch allowed these tiny organisms to thrive, and in turn, they helped the ginger grow stronger. The mulch also acted as a physical barrier against weeds, blocking sunlight so that unwanted plants could not sprout. The sugarcane plots had the fewest weeds, reducing the competition for water and nutrients that often plagues ginger crops.

The economic picture painted by the study was equally compelling. While applying mulch adds a cost to the farming process, the increase in yield and the reduction in water and labor costs for weeding made it a profitable investment. The sugarcane trash mulch generated the highest net return for the farmers, bringing in over 80,000 rupees per hectare more than the bare soil plots. It also offered the best return on investment, meaning for every rupee spent, the farmer got more than one and a half rupees back. The paddy straw mulch also performed well, though it was slightly less efficient and more expensive to apply than the sugarcane option. The wheat straw mulch helped, but it did not match the performance of the other two.

This research highlights that the choice of mulch matters deeply. It is not just about covering the ground; it is about choosing a material that lasts long enough to regulate the soil environment and feed the microbial life within it. The sugarcane trash proved to be the most persistent and effective cover, creating a cycle where better soil health led to better water use, which led to a bigger harvest and higher income. For farmers in this region, and potentially in other areas with similar climates, the study offers a practical, sustainable path forward. By using the waste from one crop to nourish another, they can protect their soil, save water, and grow a more profitable crop, all while working with the natural rhythms of the land rather than against them.