Dataset Information

Soil organic matter dynamics in semiarid agroecosystems transitioning to dryland.

ABSTRACT: Recent interest in improving soil health and agricultural sustainability recognizes the value of soil organic carbon (SOC) sequestration and nutrient cycling. The main goal of this study was to evaluate the response of various SOC and nitrogen (N) components in semiarid cropping systems transitioning from limited-irrigation to dryland and a restored grassland in the Southern High Plains of USA. Cropping systems evaluated include dryland winter wheat (Triticum aestivum L.)-sorghum (Sorghum bicolor L.)-fallow with conventional tillage (DLCTF) and no-tillage (DLNTF), limited-irrigation winter wheat-sorghum-fallow with no-tillage and cover cropping (LINTC) and no-tillage fallow (LINTF), and an undisturbed grassland (NG). Soil samples were collected from 0-15 cm and 15-30 cm depths and analyzed for SOC, total N, inorganic N, and soil microbial biomass carbon (SMBC) contents. The CO₂ and N₂O release during a eight-weeks long laboratory incubation were also analyzed. Results show 14% and 13% reduction in SOC and total N from 0-30 cm depth with the transition from limited-irrigation to dryland cropping systems while 51% more SOC and 41% more total N with the transition to grassland. The SMBC was 42% less in dryland cropping systems and 100% more in NG than the limited-irrigation cropping systems. However, the grassland was N limited, with 93% less inorganic N in NG compared to only 11% less in dryland cropping systems than in limited-irrigation cropping systems. The microbial respiration measured as CO₂-C was highest in NG, followed by limited-irrigation and dryland cropping systems. The N₂O-N release showed the lowest rate of N loss from dryland cropping systems, followed by NG and limited-irrigation cropping systems. This study demonstrated loss of SOC and N in agroecosystems transitioned to dryland crop-fallow systems, with greater magnitude of change observed in the biologically active fraction of soil organic matter. Grassland restoration could be an important strategy to increase SOC and nutrients in hot, dry, semiarid agroecosystems transitioning to dryland.

SUBMITTER: Ghimire R

PROVIDER: S-EPMC7583628 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Soil organic matter dynamics in semiarid agroecosystems transitioning to dryland.

Ghimire Rajan R Khanal Babu Ram BR

PeerJ 20201020

Recent interest in improving soil health and agricultural sustainability recognizes the value of soil organic carbon (SOC) sequestration and nutrient cycling. The main goal of this study was to evaluate the response of various SOC and nitrogen (N) components in semiarid cropping systems transitioning from limited-irrigation to dryland and a restored grassland in the Southern High Plains of USA. Cropping systems evaluated include dryland winter wheat (<i>Triticum aestivum</i> L.)-sorghum (<i>Sorg ...[more]

PMID: 33150087

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Project description:BackgroundTo promote straw degradation, we inoculated returned farmland straw with earthworms (Pheretima guillelmi). Increasing the number of earthworms may generally alter soil organic carbon (SOC) dynamics and the biological activity of agricultural soils.MethodsWe performed soil mesocosm experiments with and without earthworms to assess the decomposition and microbial mineralization of returned straw and soil enzyme activity across different time periods.ResultsWhen earthworms were present in soil, the surface residues were completely consumed during the first four weeks, but when earthworms were absent, most of the residues remained on the soil surface after 18 weeks. On day 28, the SOC content was significantly higher in the treatment where both earthworms and residue had been added. The SOC content was lower in the treatment where earthworms but no residue had been added. The organic carbon content in water-stable macroaggregates showed the same trend. During the first 14 weeks, the soil basal respiration was highest in the treatments with both residues and earthworms. From weeks 14 to 18, basal respiration was highest in the treatments with residues but without earthworms. We found a significant positive correlation between soil basal respiration and soil dissolved organic carbon content. Earthworms increased the activity of protease, invertase, urease and alkaline phosphatase enzymes, but decreased β-cellobiohydrolase, β-glucosidase and xylosidase activity, as well as significantly reducing ergosterol content.ConclusionThe primary decomposition of exogenous rice residues was mainly performed by earthworms. Over a short period of time, they converted plant carbon into soil carbon and increased SOC. The earthworms played a key role in carbon conversion and stabilization. In the absence of exogenous residues, earthworm activity accelerated the decomposition of original organic carbon in the soil, reduced SOC, and promoted carbon mineralization.

Project description:Climate change is causing larger wildfires and more extreme precipitation events in many regions. As these ecological disturbances increasingly coincide, they alter lateral fluxes of sediment, organic matter, and nutrients. Here, we report the stream chemistry response of watersheds in a semiarid region of Utah (USA) that were affected by a megafire followed by an extreme precipitation event in October 2018. We analyzed daily to hourly water samples at 10 stream locations from before the storm event until three weeks after its conclusion for suspended sediment, solute and nutrient concentrations, water isotopes, and dissolved organic matter concentration, optical properties, and reactivity. The megafire caused a ~2,000-fold increase in sediment flux and a ~6,000-fold increase in particulate carbon and nitrogen flux over the course of the storm. Unexpectedly, dissolved organic carbon (DOC) concentration was 2.1-fold higher in burned watersheds, despite the decreased organic matter from the fire. DOC from burned watersheds was 1.3-fold more biodegradable and 2.0-fold more photodegradable than in unburned watersheds based on 28-day dark and light incubations. Regardless of burn status, nutrient concentrations were higher in watersheds with greater urban and agricultural land use. Likewise, human land use had a greater effect than megafire on apparent hydrological residence time, with rapid stormwater signals in urban and agricultural areas but a gradual stormwater pulse in areas without direct human influence. These findings highlight how megafires and intense rainfall increase short-term particulate flux and alter organic matter concentration and characteristics. However, in contrast with previous research, which has largely focused on burned-unburned comparisons in pristine watersheds, we found that direct human influence exerted a primary control on nutrient status. Reducing anthropogenic nutrient sources could therefore increase socioecological resilience of surface water networks to changing wildfire regimes.

Dataset Information

Soil organic matter dynamics in semiarid agroecosystems transitioning to dryland.

Publications

Soil organic matter dynamics in semiarid agroecosystems transitioning to dryland.

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