The team, led by Mukesh Choudhary and Mahendra Prasad, compared four perennial grasses over nine consecutive growing seasons from 2015-16 to 2023-24: guinea grass (Megathyrsus maximus), a tri-specific hybrid (TSH), the bajra-napier hybrid (BNH), and the hardy rangeland grass Cenchrus ciliaris. Each species was grown under two contrasting moisture regimes, rainfed and irrigated, in a factorial randomized block design with three replications. The starting point was a sandy clay loam classified as a Typic Haplustept, with soil organic carbon of just 5.0 grams per kilogram in the top 15 centimeters, available nitrogen of 170 kilograms per hectare, and the low fertility typical of a region battered by recurrent drought, shallow undulating soils, and potential evapotranspiration of 2,565 millimeters per year.

The headline finding is that guinea grass emerged as the standout restoration champion. Under irrigation it produced a mean green fodder yield of 85.9 tonnes per hectare and dry fodder yield of 20.4 tonnes per hectare, increases of 37.0 and 28.3 percent over rainfed conditions. More importantly for soil health, irrigated guinea grass plots recorded the highest total organic carbon of any treatment, 9.56 grams per kilogram in the surface soil, along with the greatest hot water soluble carbon (146.13 milligrams per kilogram), particulate organic carbon (6.12 grams per kilogram), labile carbon (371.75 milligrams per kilogram), and soil microbial biomass carbon (365.83 micrograms per gram). These values exceeded the tri-specific hybrid, bajra-napier hybrid, and Cenchrus ciliaris by margins ranging from 2 percent to as much as 234 percent depending on the indicator.

Across all species, irrigation proved a powerful amplifier of both productivity and soil recovery. Green fodder yields rose by 11.9 to 44.7 percent under irrigation compared with rainfed conditions, and dry yields by 5.5 to 34.4 percent. Below ground, irrigation lifted total organic carbon by about 5 percent, hot water soluble carbon by roughly 19 percent, particulate organic carbon by about 12 percent, labile carbon by around 6 percent, and microbial biomass carbon by approximately 23 percent. Carbon buildup relative to the experiment’s starting conditions ranged from 3 to 41 percent under rainfed management and climbed to 5 to 49 percent with irrigation, with guinea grass and the tri-specific hybrid consistently at the top of that range. Available nitrogen, phosphorus, and potassium followed the same pattern, with guinea grass under irrigation increasing nutrient availability by 5.8 to 16.6 percent relative to its rainfed counterpart.

To move beyond single measurements, the researchers deployed two composite metrics. The carbon management index, which combines a carbon pool index with a lability index against a reference fallow soil, exceeded 185 under guinea grass in both moisture regimes, a value well above the threshold of 100 that signals sustainable soil management. Under irrigation, guinea grass posted a carbon management index 21, 45, and 75 percent higher than the tri-specific hybrid, bajra-napier hybrid, and Cenchrus ciliaris respectively. The team also introduced a restoration efficiency index, a weighted composite integrating productivity, soil fertility, microbial health, and soil carbon dynamics, with biological recovery and carbon restoration weighted at 0.30 each. Guinea grass scored above 80 percent, the study’s threshold for high restoration efficiency, in both rainfed (86.7 percent) and irrigated (84.8 percent) conditions, while Cenchrus ciliaris languished at the bottom.

Interestingly, the tri-specific hybrid revealed a different kind of strength. Although its absolute yields and carbon metrics trailed guinea grass, it suffered the smallest penalty when the irrigation was switched off: its irrigated green fodder yield of 78.6 tonnes per hectare was only 12.0 percent above its rainfed yield, and its dry yield just 5.5 percent higher. That drought resilience translated into moderate restoration efficiency under rainfed conditions, with a carbon management index of at least 150 and a restoration efficiency index above 60 percent. The authors’ practical recommendation therefore splits by context: guinea grass for maximizing biomass and soil carbon restoration wherever water allows, and the tri-specific hybrid as the more reliable choice for purely rainfed systems.

The study also probed the quality and vertical distribution of the carbon being accumulated. The recalcitrant index, the proportion of carbon resistant to acid hydrolysis, varied only narrowly, from 95.91 to 97.13 percent, with Cenchrus ciliaris and the bajra-napier hybrid tending toward slightly higher values. The authors interpret the lower recalcitrant index under guinea grass and the tri-specific hybrid not as a weakness but as evidence of active carbon cycling, with abundant labile fractions turning over rapidly in these biologically vigorous rhizospheres. In soils this depleted, they argue, carbon sink strength is limited primarily by the quantity of carbon inputs rather than by the soil’s capacity to stabilize them. Stratification ratios, comparing surface to subsurface carbon pools, ranged from 0.89 to 1.22 and trended higher under irrigation, consistent with litter, fine root turnover, and rhizodeposition enriching the upper 15 centimeters of the profile.

Correlation and network analyses added a systems-level view of how restoration proceeds. Soil organic carbon correlated almost perfectly with total organic carbon (r = 1.00) and very strongly with microbial biomass carbon (r = 0.97), particulate organic carbon (r = 0.95), labile carbon (r = 0.95), and the carbon management index (r = 0.95). Microbial biomass carbon itself tracked available nitrogen at r = 0.99. Within the correlation network, built from significant correlations of r at or above 0.85, the variables with the greatest connector importance were the carbon management index, labile carbon, microbial quotient, particulate organic carbon, and microbial biomass carbon, marking them as the most informative sentinels of recovery. The restoration efficiency index behaved differently, correlating negatively with these indicators, which the authors attribute to the mathematical structure of the composite index rather than any biological trade-off, and they candidly flag indicator redundancy and the author-defined weighting scheme as limitations requiring validation in independent datasets.

The broader significance is considerable. Land degradation undermines food security, biodiversity, and climate resilience worldwide, and restoring degraded lands is embedded in the United Nations Sustainable Development Goals. Perennial grasses work as restoration agents because their deep, persistent root networks pump carbon below ground year after year, stabilize aggregates, reduce erosion, and feed the microbial communities that drive nutrient cycling. This trial shows that species choice and water availability jointly determine how fast that recovery happens, and it offers farmers and land managers in semi-arid regions a concrete, evidence-based menu: guinea grass where biomass and carbon gains are the priority, the tri-specific hybrid where drought risk dominates. The authors caution that the study covered a limited set of species in a single semi-arid environment, that the persistence of these gains under future climate variability remains untested, and that microbial community dynamics, greenhouse gas fluxes, and economic feasibility were beyond its scope. Still, after nine years of monitoring, the message from Bundelkhand is unusually clear: the humblest of crops, a well-chosen perennial grass, may be among the cheapest and most effective tools humanity has for putting carbon, fertility, and life back into exhausted soil.

Subject of Research: Long-term comparative evaluation of perennial grass species for restoring soil carbon and fertility in degraded semi-arid agroecosystems under rainfed and irrigated conditions

Article Title: Comparative assessment of perennial grasses for restoring degraded semi-arid agroecosystems under contrasting moisture regimes

Article References: Choudhary, M., Prasad, M., Dixit, A. K., Kantwa, S. R., Mahawer, S. K., & Palsaniya, D. R. (2026). Comparative assessment of perennial grasses for restoring degraded semi-arid agroecosystems under contrasting moisture regimes. Discover Soil, 3(1), Article 182. https://doi.org/10.1007/s44378-026-00342-6

Image Credits: AI Generated

DOI: 10.1007/s44378-026-00342-6

Keywords: perennial grasses, soil restoration, soil organic carbon, semi-arid agroecosystems, carbon management index, restoration efficiency index, guinea grass, land degradation, soil microbial biomass, irrigation, fodder productivity, Bundelkhand

The research team, led by Alisha Keprate with D.R. Bhardwaj, Prashant Sharma, and Rushal Dogra, sampled soils across four contrasting land-use systems at two topographic positions — sheltered valley floors and cooler mountain slopes — and at three depths reaching down to 60 centimeters. Their study area, spanning roughly 1,543 to 2,396 meters above sea level in the Lesser Himalayan range, receives about 850 millimeters of annual precipitation, mostly from the southwest monsoon, and its Brown Podzolic soils sit on slopes of 15 to 35 percent. This combination of high rainfall, rugged relief, and intensive smallholder farming makes the region a natural laboratory for studying how land management reshapes one of the planet’s largest terrestrial carbon pools.

Soil organic carbon is not a single substance but a family of fractions that differ sharply in how quickly they turn over. The researchers used a modified Walkley-Black oxidation procedure, applying sulfuric acid at increasing concentrations to separate very labile, labile, less labile, and non-labile carbon pools. The two most easily oxidized fractions together form the active pool, which fuels rapid nutrient cycling, while the more resistant fractions make up the passive pool, the long-term reservoir that locks carbon away for decades or centuries. Alongside these fractions, the team computed the lability index, carbon pool index, and carbon management index — composite metrics that translate raw chemistry into practical measures of soil health and management performance.

The results were striking. Agroforestry plots, in which ten-to-fifteen-year-old apple trees grow alongside annual crops such as peas, beans, rajmash, potatoes, and barley, recorded the highest total organic carbon at 19.83 milligrams per gram of soil — roughly 50 percent more than adjacent agricultural plots growing potatoes, peas, and barley, and more than double the 9.72 milligrams per gram found on barren reference land. Apple monoculture orchards fell in between at 17.71 milligrams per gram. The same hierarchy held for nearly every carbon fraction: the active carbon pool reached 11.26 milligrams per gram under agroforestry compared with just 4.38 on barren land, while the passive pool peaked at 8.57 milligrams per gram in the tree-based system. Soil carbon density followed suit, climbing to 48.59 megagrams per hectare under agroforestry against a meager 25.59 on barren ground.

The carbon management index told an even more compelling story. Relative to the barren reference, the index rose by 137 percent under agroforestry, 114 percent under horticulture, and 44 percent under agriculture. Because this index integrates both the size of the carbon pool and the lability of its constituent fractions, the authors argue it captures a genuine improvement in the quantity and quality of soil carbon under tree-based management. The mechanism, they suggest, is a steady supply of organic matter — leaf litter, pruning residues, root biomass, and root exudates — that feeds microbial communities, promotes stable soil aggregates, and builds organo-mineral associations. Apple leaf litter, rich in phenolic compounds, may further slow decomposition and favor gradual nutrient release, tipping the balance toward carbon stabilization rather than loss.

Topography proved to be a second, independent sculptor of soil carbon. Valley soils, warmer and biologically livelier, held more of the fast-cycling active fractions: very labile carbon reached 5.14 milligrams per gram there, against 3.99 on mountain slopes, and the active pool overall measured 9.08 versus 6.73 milligrams per gram. Mountain soils, by contrast, accumulated more of the recalcitrant material — the passive pool reached 9.04 milligrams per gram on slopes compared with 5.39 in valleys, and non-labile carbon rose to 3.65 milligrams per gram. The researchers attribute this split to cooler slope temperatures that suppress microbial mineralization, strengthen the adsorption of organic matter onto clay minerals, and favor fungal communities that convert labile substrates into stable, microbial-derived organic matter. In effect, valleys recycle carbon quickly while mountains bank it.

Depth added a third dimension to the pattern. Total organic carbon declined steadily from 17.64 milligrams per gram in the surface 0-to-20-centimeter layer to 12.86 at 40-to-60 centimeters, and the active fractions fell in parallel, reflecting the concentration of litter and root inputs near the surface. Yet the non-labile fraction moved in the opposite direction, rising from 2.10 to 3.88 milligrams per gram with depth — a signature of older, more persistent carbon that has escaped rapid decomposition in the subsoil. A principal component analysis confirmed the split, with the first two axes explaining 56.4 percent of total variance and cleanly separating surface, labile, nitrogen-rich soils from deeper horizons dominated by passive fractions.

Nitrogen dynamics mirrored the carbon story. Total nitrogen was highest under agroforestry at 0.092 percent, and soil nitrogen density peaked at 2.27 megagrams per hectare in the tree-crop system, compared with 1.93 under agriculture and 1.94 on barren land. Valley soils again outpaced mountain soils, and all nitrogen measures declined with depth. Ammoniacal nitrogen reached 66.11 milligrams per kilogram under agroforestry, while nitrate nitrogen was highest in horticultural orchards at 61.44 milligrams per kilogram — a difference the authors link to heavy fertilizer inputs and the absence of intercropped plants competing for nitrate uptake in monoculture orchards. Correlation analysis reinforced the coupling of the two nutrient cycles: total organic carbon and total nitrogen were strongly positively correlated, and the carbon management index tracked closely with both carbon lability and nitrogen availability.

Taken together, the findings carry a clear message for the fragile mountains of the Himalayas and beyond: converting conventional annual agriculture to apple-based agroforestry could simultaneously enlarge the soil’s carbon bank, improve its nitrogen capital, and boost the overall carbon management index — a trifecta for climate-resilient mountain farming. The authors caution that their study reflects a single sampling period and that the underlying biological and physicochemical mechanisms were inferred rather than directly measured. Even so, in a region where steep slopes, erodible soils, and shifting land use threaten both livelihoods and carbon stocks, the evidence that mixing trees with crops builds richer, more stable ground adds scientific weight to a strategy many Himalayan farmers have practiced for generations — and gives policymakers a quantified reason to encourage it.

Subject of Research: Effects of land-use type, topographic position, and soil depth on soil organic carbon fractions and nitrogen dynamics in the wet temperate northwestern Himalayas

Article Title: Land-use and topographic effects on soil carbon and nitrogen fractions across contrasting land-use systems in the wet temperate northwestern Himalayas

Article References: Keprate, A., Bhardwaj, D., Sharma, P., & Dogra, R. (2026). Land-use and topographic effects on soil carbon and nitrogen fractions across contrasting land-use systems in the wet temperate northwestern Himalayas. Journal of Agriculture and Food Research, 31, Article 103262. https://doi.org/10.1016/j.jafr.2026.103262

Image Credits: AI Generated

DOI: 10.1016/j.jafr.2026.103262

Keywords: soil organic carbon, agroforestry, carbon fractions, carbon management index, soil nitrogen, northwestern Himalayas, land use change, topography, apple orchards, carbon sequestration, soil depth, climate-resilient agriculture