Soil Type Modifies the Impacts of Warming and Snow Exclusion on Carbon and Nutrient Losses

The varied and wide-reaching impacts of climate change are occurring across heterogeneous landscapes. Despite the known importance of soils in mediating biogeochemical nutrient cycling, there is little experimental evidence of how soil characteristics may shape ecosystem response to climate change. Our objective was to clarify how soil characteristics modify the impact of climate changes on carbon and nutrient leaching losses in temperate forests. We therefore conducted a field-based mesocosm experiment with replicated warming and snow exclusion treatments on two soils in large (2.4 m diameter), in-field forest sapling mesocosms. We found that nutrient loss responses to warming and snow exclusion treatments frequently varied substantially by soil type. Indeed, in some cases, soil type nullified the impact of a climate treatment. For example, warming and snow exclusion increased nitrogen (N) losses on fine soils by up to four times versus controls, but these treatments had no impact on coarse soils. Generally, the coarse textured soil, with its lower soil-water holding capacity, had higher nutrient losses (e.g., 12-17 times more total N loss from coarse than fine soils), except in the case of phosphate, which had consistently higher losses (23-58%) from the finer textured soil. Furthermore, the mitigation of nutrient loss by increasing tree biomass varied by soil type and nutrient. Our results suggest that potentially large biogeochemical responses to climate change are strongly mediated by soil characteristics, providing further evidence of the need to consider soil properties in Earth system models for improving nutrient cycling and climate projections.

Manure Application Timing and Tillage Influence on Nutrient Loss from Snowmelt Runoff

Winter manure application contributes substantial nutrient loss during snowmelt and influences water quality. The goal of this study is to develop best management practices (BMPs) for winter manure management. We compared nutrient concentrations in snowmelt runoff from three dates of feedlot solid beef manure application (November, January, and March) at 18 tons ha−1 on untilled and fall-tilled plots. The manure was applied at a single rate. Sixteen 4 m2 steel frames were installed in the fall to define individual plots. Treatments were randomly assigned so that each tillage area had two control plots, two that received manure during November, two in January, and two in March. Snowmelt runoff from each individual plot was collected in March and analyzed for runoff volume (RO), ammonium-nitrogen (NH4-N), nitrate-nitrogen (NO3-N), total suspended solids (TSS), total Kjeldahl nitrogen (TKN), total phosphorus (TP), and total dissolved phosphorus (TDP). Snowmelt runoff concentrations and loads of NH4-N, TKN, TP, and TDP were significantly higher in runoff from manure application treatments compared to control. The concentration of NH4-N and loads of NH4-N and TDP were significantly (p = 0.05) greater (42%, 51%, and 47%, respectively) from untilled compared to fall-tilled plots. The November application significantly increased RO, NH4-N, and TDP concentrations and loads in the snowmelt runoff compared to January and March applications. Results showed that nutrient losses in snowmelt runoff were reduced from manure applications on snow compared to non-snow applications. The fall tillage before winter manure application decreased nutrient losses compared to untilled fields.

The Effect of Soil Conservation Measures on Runoff, Soil Erosion, TN, and TP Losses Based on Experimental Runoff Plots in Northern China

Total nitrogen (TN) and total phosphorous (TP) are the main pollutants affecting the water quality of the Miyun Reservoir, Beijing. However, few studies have been conducted on their responses to implemented soil conservation measures at a slope scale in northern China. To explore the impact of soil conservation measures on TN and TP losses, field monitored data from 18 runoff plots under natural rainfalls were used to analyze the changing characteristics of runoff, soil loss, and nutrient losses during 2014–2019. The results indicated that runoff, soil erosion, as well a TN and TP losses from the plots varied significantly, depending on land use and soil conservation measures. Bare plots suffered the highest soil, TN, and TP losses, followed by cultivated plots without soil conservation measures, cultivated plots with contour tillage, and other plots. Event-averaged runoff and soil loss rates ranged from 0 to 7.9 mm and from 0 to 444.4 t km−2 yr−1, and event-averaged TN and TP losses from cultivated plots were the highest, with values of 39.8 and 3.0 kg km−2, respectively. Bare and cultivated plots were the main sediment and nutrient sources. Among the cultivated plots, the terraced plot had the lowest soil and nutrient losses. The vegetated plots had insignificantly lower soil and nutrient losses. Most TN and TP were lost in particulate status from the plots, especially from the plots with soil conservation measures. Soil conservation measures can effectively prevent TN and TP losses. To guarantee water resource use, contour tillage is preferred for the bare and cultivated lands in the study region.

Impacts of Low Disturbance Liquid Dairy Manure Incorporation on Alfalfa Yield and Fluxes of Ammonia, Nitrous Oxide, and Methane

Surface applied liquid dairy manure application (i.e., broadcasting) after alfalfa (Medicago sativa L.) harvest is a common practice. Low disturbance manure incorporation (LDMI) may offer multiple benefits including lower ammonia (NH3), greenhouse gas (GHG) and hydrologic nutrient losses compared to broadcast. However, few studies have simultaneously quantified LDMI impacts on alfalfa yield, NH3 and greenhouse gas (GHG) fluxes. We measured NH3, nitrous oxide (N2O), and methane (CH4) fluxes for liquid dairy manure treatments applied to alfalfa plots for broadcast and LDMI over three seasons (2014 to 2016) in central Wisconsin, USA. There were minor differences in alfalfa yield and nitrogen (N) uptake across treatments and years. Shallow disk injection and aerator/band reduced NH3 loss by 95 and 52% of broadcast, respectively, however both substantially increased N2O fluxes (6 and 4.5 kg ha−1 year−1 versus 3.6 kg ha−1 year−1 for broadcast, respectively). The magnitude and timing of N2O fluxes were related to manure application and precipitation events. Average CH4 fluxes were similar among methods and increased with soil moisture after manure application. Results highlight the importance of quantitatively evaluating agri-environmental tradeoffs of LDMI versus broadcast manure application for dairy farms.

Effects of Crop–Hedgerow Intercropping on the Soil Physicochemical Properties and Crop Yield on Sloping Cultivated Lands in a Purple Soil of Southwestern China

Crop–hedgerow intercropping systems are important agroforestry systems for preventing soil degradation and soil nutrient losses on sloping cultivated land in the Three Gorges Reservoir (TGR) area of China. However, the mechanism by which hedgerow spatial layouts and the planting patterns affect soil nutrients and crop yields is still uncertain. A two-year field experiment was performed on a 10° slope to investigate the effects of slope position and different crop–hedgerow intercropping systems on soil physicochemical properties and crop yields. The treatments were a two-belt mulberry contour hedgerow (TM), a two-belt compound mulberry–vetiver hedgerow (TCMV), a two-belt compound mulberry–alfalfa hedgerow (TCMA), a seven-year-old two-belt mulberry contour hedgerow (7YTM), a seven-year-old mulberry border hedgerow (7YBM), a seven-year-old pure mulberry (7YPM), and a control treatment (CT, no hedgerows). In all treatments, except 7YPM, there was a significant (p < 0.05) increase in crop yield, clay content, soil total nitrogen (STN), acid-hydrolyzable nitrogen (AHN), and soil organic carbon (SOC) with declining slope position, whereas soil bulk density (BD), sand content, and soil pH showed the opposite trend. In TM, TCMV, TCMA, and 7YTM, the mustard yields and soil properties were better than those in CT, and there was no significant (p > 0.05) difference in mustard yield or soil properties between the upper-middle and lower-middle slope positions. Compared with CT, TCMV, and TCMA increased mustard yields by 8.28% and 9.86%, respectively, while 7YTM, 7YBM, and 7YPM reduced mustard yields by 7.69%, 17.69%, and 29.73%, respectively. TCMV and TCMA were confirmed to be viable intercropping systems for significantly reducing nutrient losses, improving soil quality, and changing soil nutrient distributions to maintain optimum crop yields on sloping lands.

Assessment of Sediment and Nutrient Losses from Forest, Pasture, Tea and Cropped Farms along the Nyondo River Basin

The widespread poor agricultural practices and ancient technologies continuously aggravate erosion of sediments and soil nutrients from delicate terrains at the major catchments of water shades. The ongoing study is assessing soil and nutrient losses in the four major land use covers (forest, pasture, tea and maize farms) in the upper catchment of Nyondo River Basin. The study sites in the upper catchment of Nyondo River Basin are densely populated and receive bimodal rains that support agriculture which is the main economic activity supporting livelihoods of the communities in the region. The experiment is laid in a randomized complete block design (RCBD) with each of the land use covers replicated 3 times with erosion traps mounted on 150 m2 plots. First data set was collected during the short rainy season of 2019 and long rainy season of 2020, with subsequent data collection continuing up to the short rainy season of 2021. Preliminary results showed that soil and nutrients were significantly lost in maize fields (p=0.05), forest cover was the least vulnerable while pasture cover had the highest surface runoff. Nutrient concentrations in the eroded sediments (p=0.05) were significantly higher than those that remained in maize plot while forest and tea fields registered comparable effectiveness in reducing both soil and nutrient losses, seasons notwithstanding. Pasture and maize fields had the highest water loss due to low infiltration rate and were also vulnerable to sediment and nutrients loss through surface runoff. The information will be used to inform and advise stake holders on land use policies geared towards attainment of sustainable agriculture and water quality in Nyondo and areas with similar landscapes and agricultural practices. Keywords: Erosion; Sediment; Nutrients; Land use

Metadata Analysis to Evaluate Environmental Impacts of Wheat Residues Burning on Soil Quality in Developing and Developed Countries

Crop residues are widely considered as a biofuel source and used in livestock feeding, or are burned off to clean the field for tillage and planting. Nonetheless, crop residue burning poses serious threats to the soil stability and sustainability of the food chain. This study aimed to investigate the potential environmental impacts of wheat residues burning on declines in soil quality in developing (Iran) and developed (Italy) countries by analyzing metadata of the last 50 years. All metadata were provided from the ‘Food and Agriculture Organization of the United Nations’ (FAO) including wheat harvested area, annual production, and biomass burning, to assess the potential impact of crop residue burning on soil quality. In detail, the greenhouse gases (GHGs) emission, and energy and nutrient losses by the wheat residues burning were estimated. Our results showed a robust interdependence between wheat residues burning and environmental effects in both developed and developing systems. Accordingly, the global warming potential increased in Iran (4286 to 5604 kg CO2eq) and decreased in Italy (3528 to 1524 kg CO2eq) over the last 50 years. Amongst all nutrient losses, nitrogen represents the higher lost value in both countries, followed by potassium, sulfur, and phosphorus.