Soil Quality Lab

Legume seeds (e.g. soybean, common bean, peanut, lentil and pea) are the main source of dietary protein for billions of people around the world. Soybeans are also vital for the production of non-ruminant livestock (poultry and pork) that in turn provide a second major source of human dietary protein. The utilization of legume protein by people (and non-ruminant livestock) is often limited by the proportion of methionine and cysteine, two essential sulfur-containing amino acids in that protein. Plant breeders have had little success in improving the level of methionine and cysteine in legume seed proteins. We found no literature on research to increase these amino acids through field-scale agronomic management of sulfur fertility. Enhancing the content of these two amino acids in legume crops could lead to enhanced child health and growth in low-income countries (and vegetarian populations). It could also lead to more efficient production of poultry and pork. Sulfur deficiency in crops is common in many parts of the world, especially in Africa, and is increasingly common in North America since the successful implementation of sulfur dioxide air pollution control during the past three decades.

We conducted a survey of commercial soybeans grown in Maryland and found a nearly two-fold range in methionine+cysteine contents of the seed and a strong correlation between the contents of those amino acids and S in the seeds. We then conducted S fertilization experiments with several varieties of soybeans grown on two sandy coastal plain soils using four fertility treatments: control (no sulfur added), gypsum applied prior to planting as a powder on the soil surface (29.1 kg S/ha), Epsom salt applied as a foliar spray during early flowering (13.5 kg S/ha), and the combination of gypsum + Epsom (42.6 kg S/ha). Averaged across four experiments, the yield was significantly increased by all three S treatments, with the control yielding 2,662 kg/ha, gypsum 3,152 kg/ha, Epsom 3,131 kg/ha, and gypsum+Epsom 3,368 kg/ha. The % methionine + cysteine in the seed dry was significantly increased as well by the S treatments: control 0.29%, gypsum 0.37%, Epsom 0.50%, and gypsum+Epsom 0.43%. The total amount of methionine + cysteine produced per ha of and was nearly doubled by applying just 13 kg S as a foliar spray. This project has shown that S fertilization can substantially increase the nutritional quality of soybean protein as well as the yield. These results are especially relevant to organic soybean producers as synthetic supplementation with methionine in poultry and pig feed is not allowed in organic farming.

We aim to expand our research on sulfur to other parts of the world (especially Africa) and other grain legumes (such as dry beans, lentils, etc.) commonly consumed directly in human diets. Considering sulfur in crop nutrient management could improve grain legume yields, farmer profitability, and the nutritional quality of human and animal diets.

Cover crops are plants grown to increase the quality and productivity of the soil as well as increase the amount of carbon sequestered from the atmosphere. We are developing new cover crops, such as the Forage Radish, that can provide a wide range of benefits including the alleviation of soil compaction by root bio-drilling, the capture of excess nitrogen to prevent water pollution and its subsequence release to reduce fertilizer requirements, the suppression of weeds to reduce the need for tillage and herbicides, and the regulation of the soil microbial system to enhance synergies and inhibit pathogens.

Due partially to its generous cost-share program, Maryland the highest proportion in the US of cropland acres cover cropped. However, farmers typically plant cover crops after cash crop harvest, which our research shows is usually too late to effectively prevent nitrogen leaching during the winter or provide enough cover to adequately control overwinter erosion. Our research shows that aerial or ground based interseeding into standing crops, choosing earlier-maturing corn and soybean cultivars, and making other adjustments to the farming system may allow earlier cover crop establishment.

Many farmers also cut short cover crop growth potential in spring by terminating cover crops as early as possible, commonly in late March or early April. Such termination is too early to allow the cover crops to optimally promote soil health, water conservation and crop yield. Delaying spring cover crop termination until optimal cash crop planting time, especially planting green instead of killing cover crops two to four weeks ahead of planting, could allow both timely cash crop planting and extended cover crop growth. Potential benefits of greater cover crop biomass growth include short-term benefits such as greater nutrient cycling, better weed-suppression, and more effective water-conserving in summer, in addition to longer-term benefits of increased soil organic matter and biological activity.

To study long-term effects of enhanced cover-cropping, two replicated experiments using adaptive management are established on sandy soil and silty soils. Main plots are a corn-soybean cropping system with each crop represented each year. These are split into three subplots featuring enhanced cover cropping using radish-clover-rye mixture, or pure rye, or no cover crop. Enhanced cover cropping involves interseeding to establish cover crops earlier so that substantial growth in fall will capture nutrients and protect soil over winter. In Spring, enhanced cover cropping includes growing cover crops up to or even beyond cash crop planting. These subplots are further divided into three sub-subplots which are used for early, mid and late cover crop termination when planting soybean and 0, 75 and 150 kg/ha levels of nitrogen fertilization when planting corn. A third site is established with only four treatment plots that are much larger (35 x 100m) in size and run down-slope on sandy soil into a forested wetland. This is also a corn-soybean system with either enhanced cover cropping or standard cover cropping. Transects of groundwater wells are installed running from the center of the field, at the edge of the field and in the forest downhill from the field. The wells in the field are protected by cast-iron manholes buried below the soil surface so that they can remain in the field for continuous long-term sampling despite agricultural machinery operations. Also installed under the manholes are suction lysimeters, and soil water and temperature sensors. The parameters being measured in this complex experiment include cover crop performance, crop yields, runoff water amount and nutrient content, percolation water nutrients sampled with suction lysimeters, groundwater level and nutrient content, and ecological observations on pests, nutrients, plant condition and soil health.

Organic production, per se, may not reduce environmental impacts such as sediment and nutrient loss and greenhouse gas emissions. However, organic grain production, if done regeneratively, may minimize these environmental impacts and provide substantial ecosystem services. Among these, nutrient loss reduction is vitally important given that about 40% of nutrient pollution to the Chesapeake Bay comes from agriculture. Other ecosystem services from regenerative organic farming may include carbon sequestration, soil erosion control, protection of above and below-ground biodiversity, and provision of clean water to aquifers and streams. This project studies a suite of practices that make organic farming more regenerative than typically practiced. Therefore, the adoption of organic farming presents a rare opportunity for grain farmers, especially those on the Delmarva Peninsula, to realize increased income as well as potentially provide better stewardship of their land and water.

This project's overall aim is to develop strategies and practices to minimize soil disturbance, environmental impacts, and input costs while providing profits during the transition comparable to those realized under conventional grain farming. This is an integrated research-extension project to mentor transitioning farmers and develop systems to minimize soil disturbance, environmental impacts, and input costs while providing profitability during the transition period. The research goal is to compare four transition strategies along a continuum of soil disturbance, soil cover, and input cost. These are being replicated in farm equipment scale plots on contrasting soil at two research stations and on two commercial farms. They are evaluated for effects on soil health, leaching and runoff nutrient loss, crop yields, profitability, and ease of management. In order of least to most disturbance, the four systems are 1) Perennial alfalfa-grass hay, untilled; 2) Minimum-till corn-soybean-wheat rotation with precision-zoned high-biomass diverse cover crops; 3) Reduced-till corn-soybean-wheat with high-biomass cover crops; and 4) Traditional full-tillage organic soybean-corn, with simple cover crops and input substitution (using organic-approved forms of the same types of inputs used by conventional farms). The project assesses the impacts of these transition strategies on soil health, farm profitability, and crop productivity. It includes an outreach component in collaboration with a grassroots farmer organization that involves farmers in the research and employs experienced organic grain farmers in mentoring farmers who are interested in learning how to transition to organic production.

Soil quality is a concept that integrates soil physical, biological and chemical properties in a way that describes the capacity of the soil to provide such ecosystem functions as plant productivity, water purification and carbon sequestration. Optimizing the amount and quality of soil organic matter is often critical for improved soil function. We are researching sustainable farming systems that manage soil organic matter and enhance profitability, environmental quality, and food production. We are also developing robust methods that can be used in the field to assess the impact of agricultural practices on soil quality.

Research Area(s): Biology and Ecology of Soils, Soil Chemistry and Biochemistry, Soil Microbiology, Soil Quality.

Soil Quality (SQ) is rapidly joining air and water quality as a major goal of natural resource management. A practical measure of SQ should emphasize soil properties that are affected by agronomic practices. Most of the functions associated with soil quality are strongly influenced by soil organic matter, especially the small portion (usually < 10% of total C) that is partially processed and stabilized by microbes but still considered active organic C. This research integrates key chemical, physical and biological soil measurements, as well as experience-based judgements by farmers, into SQ assessments that are sensitive to management. One of the early contributions from this work was the dilute potassium permanganate reactive carbon test, for which we developed both lab and field protocols. This test, sometimes termed “Weil Carbon” is now widely used and usually known as POXC - permanganate oxidizable carbon. In hundreds of published studies around the world, this test has usually proved to be one of the most sensitive to changes in soil management and most meaningful for diagnosing soil health.

A collaboration with the Tully Lab at UMD and Debre Birhan University

This transdisciplinary project aims to enhance ecosystem health in the Central Highlands of Ethiopia. The target landscape is a complex traditional farming system in which the land has suffered erosion and degradation over the past century of intensive farming and deforestation. Yet this is a region of potentially productive soils and good rainfall (800-1000 mm of rain annually). The current low productivity farming system contributes to the continued degradation of land and water resources. Deforestation is nearly complete and the few trees in the landscape are exotic species that have been planted for fuelwood and construction material (poles). A significant portion of the landscape is devoted to communal grazing and the entire landscape is heavily overgrazed. Forage vegetation is highly degraded, leading to decreased carrying capacity and ever-increasing pressure on the remaining vegetation and soils in a downward spiral of degradation. In addition to cutting firewood, people also use crop residues and dried animal manure as fuel for cooking. Thus, organic carbon and nutrient resources that could be returned to build soil health are instead removed from the productive parts of the landscape. Animal production is a major part of the farming system both for meat (and some milk) as well as for traction power. A team of two oxen are used to make as many as eight tillage passes so it is not unusual for 6 weeks of the rainy season to go by while tillage is performed, and soils are eroded before the Teff and wheat crops are even planted.

The repeated tillage leads to severe soil degradation and the large numbers of oxen and supporting cattle required for tillage subsequently lead to soils impoverishment because crop residues are removed as feed for these animals. Very few outside fertilizer inputs are available or affordable to replace the continuous removal of nutrients from the main crop fields. The results of these interactions include food scarcity and low nutrient content of food. This includes low quality of legume protein due to low levels of sulfur in soil, plants and proteins (limiting levels of methionine). We aim to develop an integrated landscape ecology approach in collaboration with local residents and scientists, including at Debre Birhan University, to include integrated soil, crop, nutrient, animal, biofuel, energy, social and natural resource management across whole communities and landscapes.

Dairy farming in the United States has become increasingly capital-intensive, using management schemes that confine large herds of highly productive dairy cows on a small part of the farm while practicing high-input crop production on most of the land. Large machines harvest the crops and bring them to the cows while other machines haul the cow manure out to the fields to fertilize the soil. Most US dairy farms are based on such confined feeding practices. To be profitable, these farms generally use economies of scale and high milk production from a large herd to support the extensive infrastructure required. With increased herd size, a significant portion of the feed is usually purchased and imported, leading to potential nutrient loading on the farm. In a reversal of this 20th century trend, during the first two decades of the 21st century an increasing number of US mid-Atlantic region dairy farms are utilizing grazing rather than confined feeding systems, largely because gazing systems require less capital investment and are often more profitable. Concerns over N loss have focused on leaching to groundwater, especially in grazing systems, where dairy cows directly release urine and manure onto pasture.