Meyer Speaker Presentation Content

Nitrogen application guidelines for crop producers in Wisconsin are economically based. Nitrogen applied in excess of crop need can be lost to the environment, which primarily occurs through NO₃^- leaching in sandy irrigated soils in WI. Excess NO₃^- in groundwater has negative environmental and human health impacts. Wisconsin nutrient application recommendations were developed on a Plainfield sand with 1% SOM. Current WI recommendations for field corn and other crops do not consider SOM mineralization as a plant N source suggesting a need for more research to examine its role in plant available N pools and NO₃^- leaching. The objective of this study is to quantify the relationship between N mineralization of SOM and N loss to NO₃^- leaching. Soil and plant samples were collected biweekly throughout the 2019 growing season from three sites along a gradient with SOM contents of 5, 10 and 13%. Sites were planted in field corn, on an irrigated vegetable farm in central WI. An anaerobic soil incubation with a pre and post KCl extraction was used to quantify potentially mineralizable N as well as soil extractable N. Total inorganic N ranged from 28 to 55 mg kg^-1 N and total mineralized N ranged from 94 to 200 mg kg^-1 N over the growing season. Initial results seem to indicate a positive relationship with SOM and N mineralization. With an increase in SOM content, an increase in potentially mineralizable N was observed. Plant samples will be analyzed for total N via dry combustion and plant uptake will be examined. Soil extractable, potentially mineralizable, and plant tissue N data along with fertilizer rate and leachate and irrigation water NO₃^- concentrations should allow for a quantification of inputs and outputs of N within this agroecosystem to better understand SOM mineralization’s role in NO₃^- leaching.

Recent studies have shown maize yields have a strong negative response to extreme heat and a weak response to rainfall in a rainfed system. However, these studies mainly account for accumulation of temperatures above 30 ^oC and seasonal precipitation, ignoring the role of concurrent rainfall can reduce the heat effect when extreme heat occurs. Here, we use a panel regression model to quantify the contribution of rainfall to reduce the heat sensitivity of crop yields based on historical data spanning from 1981 to 2020. We present that the co-occurrent rainfall could weaken heat sensitivity by 32% on average during maize growing season. The impact of average national yields projected from a 2^oC warming could be additionally reduced by 10% on average when considering rainfall effects, suggesting an important role of rainfall patterns in regulating the impacts of warming on yields. Our results have implications for assessing climate and climate change impacts on crop yields.

Quantifying crop residue decomposition improves our understanding of carbon (C) storage and nutrient cycling within agroecosystems, along with providing valuable data for model development and validation. The objective of this three-year study was to quantify the decomposition and nutrient release dynamics under field conditions of post-harvest residues from a variety of annual crops grown in Saskatchewan: barley, wheat, oats, field pea, lentil, faba bean, soybean, canola, flax, and hemp. Litter bags were placed on the soil surface in the fall, prior to snowfall, and then collected after four time intervals (six months, one year, two years, and three years), for modelling the rates of mass loss and release of nitrogen (N), phosphorus (P), potassium (K), and sulphur (S). After three years, the differences in mass loss (33-87%) and cumulative N, P, K, and S release (-24 to 91%) among the crop residues, were attributed to variation in the specific surface area and quality among residues. Average residue N, P, K, and S additions to the soil nutrient pool differed among nutrients (14, 2, 15, and 3 kg/ha, respectively) and crop residues. Unlike the legume and oilseed crop residues, which contributed N via net mineralization (22 and 16 kg N/ha, respectively), the cereal crop residues either supplied much less N (approximately 5 kg N/ha for barley and wheat) or continuously immobilized soil N (-4 kg N/ha for oats). There were no apparent P, K, and S release trends among residues. Despite similar mass (and C) losses, there were considerable differences in nutrient release among crop residues after three years, with initial residue quality being an important factor controlling decomposition and nutrient release. Generally, the cereal residues (especially oats) are decomposing and releasing nutrients slower than other residues, primarily explained by wider C:nutrient ratios.

Will edit later

Information is sparse on cycling of macro- and micronutrients by cover crops. We analyzed tissue from single species (radish and oat) and an interseeded 12-species mix (four grasses, four legumes, four brassicas) each on two fields of contrasting soils. In spring cover crop biomass was collected by individual species and also grouped by family. In late fall, cover crop biomass was collected by plant family. Concentrations of calcium (Ca), magnesium (Mg), sulfur (S) and boron (B) were influenced mainly by plant tissue type, rather than soil, while the reverse was true for nitrogen (N), phosphorus (P), potassium (K), and copper (Cu). In fall, N was 2.5% in legumes, 2% in brassicas and 1.7% in grasses. Brassicas averaged 0.5% S while grasses and legumes averaged only 0.2% S. Brassicas also had higher P, K and Ca than grasses or legumes. Brassica and legume B was 4x higher in grass B. The N/S ratio was 15 in legumes but only 4.5 in brassicas. The Ca/Mg ratio was 6.6 in brassicas but only 3.6 in grasses. The S/B ratio was 289 in grasses and only 81 in legumes. At flowering in spring, N and S averaged 2.4 and 0.2% in legumes and 1.2 and 0.3% in brassicas and 1.2 and 0.1% in grasses. Compared to grasses, brassicas and legumes were 2x higher in Ca and 3x higher in B. Grasses had highest K/Mg and S/B ratios in spring, but lowest Ca/Mg ratio. Trends for families were similar in fall and spring. Five weeks after termination, the 12-species cover crop increased Mehlich3-extractable S, P, Cu, manganese, Ca, and zinc in 0-10 cm soil. Other extracted nutrients and soybean yields were not significantly affected. This information should help farmers select cover crops to reduce nutrient limitations.

The accumulation of cadmium (Cd) in grains and edible parts of crops growing in Cd contaminated soils lead to a risk to human health. Because rice is the staple food of more than half of the world population, reducing Cd uptake by rice is critical for food quality and safety. HydroPotash (HYP), an innovative potassium fertilizer produced with hydrothermal process, possesses the characteristics for immobilizing heavy metals and has potential to be used for remediating Cd contaminated soils. The objective of this study was to evaluate the HYP as a soil amendment to immobilize Cd in an acidic soil and reduce the accumulation of Cd in rice tissues. The experiment was carried out in a greenhouse with a Cecil sandy loam soil (pH 5.3 and 3 mg Cd kg^-1) under either the flooding (4 cm above the soil surface) or field capacity. Two hydrothermal materials (HYP-1 and HYP-2) were compared with zeolite, K-feldspar + Ca(OH)₂ (raw material used for producing HYP), Ca(OH)₂, and control (without amendment). HydroPotashs, raw material, and Ca(OH)2 increased pH and electrical conductivity of soil solution collected 30 days after application of treatments. These materials reduced soluble concentration of Cd (up to 99.7%) meanwhile zeolite did not differ from control (p < 0.05). The water level did not affect the Cd concentration in soil solution (p < 0.05), but at flooded conditions, plant growth was favored. HydroPotash-1 was more effective for increasing dry biomass compared to other amendments under both water levels. HYPs reduced soluble Cd and Cd content in plants after 30 days of soil cultivation. Pending analyses are expected to prove the efficiency of HYP in reducing Cd accumulation in rice grain.

There is a disconnect between people and soil, especially in urban areas. For example, rarely do policy makers, planners, and urban residents consider soils as a living resource, capable of providing ecosystem services such as carbon sequestration and stormwater retention. Furthermore, urban scientists lack understanding in regards to how people view and interact with soil systems, limiting the relevance of urban soil research.

To explore the relationship urban residents have with their soil, TreePeople launched the “Healthy Soils for Healthy Communities” community-based soil initiative in Los Angeles (LA), CA. The objectives of this initiative are to: 1) elevate healthy soils as the “brown” in green infrastructure; 2) increase awareness of the importance of healthy soils among residents, professionals, educators, and policy-makers; 3) conduct cutting-edge research to fill the information gaps and inform education and policy; 4) facilitate urban soil-related policy changes; and 5) empower communities with science-based information, best management practices, and practical tools. The first phase of this initiative was to conduct a needs assessment aimed at: 1) determining the current status of Los Angeles’s soil health; 2) identifying the most pressing soil issues and community needs through community consultation and outreach; and 3) providing a framework for future work regarding urban soil research, policy, public education and community engagement in the region. Four online surveys were developed and disseminated to residents, policy-makers, soil-related professionals, and educators in LA County to determine their needs, knowledge, current practices, and priorities. Results from the surveys will be discussed in terms of their practical applications to increasing awareness, behaviors, and policies that promote soil health on a county-wide basis.