Performing Department
Plant Sciences
Non Technical Summary
Dryland agriculture is important to the livelihoods of many people despite the fact that it has to be carried out in resource-limited and challenging environments. Winter wheat is the primary cash crop even though yields are low reaching 20 to 35 bushels per acre. No-till seems like a viable soil conservation practice, however, it does not have the magnitude of the impact as in other wheat-growing regions. Low adoption of this practice is often associated with even more reduced yields, low surface residue retention due to strong winds, reliance on high inputs for weed control and accumulation of salts beneath the soil surface. On the other hand, there are anecdotal reports of producers successfully using other soil conservation practices, namely cover crops, in western North Dakota, western Nebraska and eastern Colorado to increase soil organic matter content (SOM) and soil health, but published research articles provide limited information. There are some cases of local farmers who have experimented with cover crops and noticed improved benefits to soil health. It is still unknown how the synergistic effect of reducing tillage and using cover crops will work in this region, and whether one or the other practice should be recommended where soils are marginal and precipitation low and sporadic.Our goal is to evaluate whether cover crops, reduction of tillage or a combination of both can be viable practices for dryland crop rotations in the Central High Plains in order to improve soil quality and soil health. Specific objectives include: (1) Evaluate integrated cover crops/tillage scenarios on crop yields and, (2) Evaluate their effects on soil properties and processes that indicate soil quality and soil moisture. The region of interest falls into two distinctive precipitation zones where available soil moisture is either critically low or where slightly greater moisture allows for increased crop productivity and crop rotational diversity. New knowledge on management strategies that incorporate use of cover crops and variable tillage reducing practices are much needed as it is still unclear what are the main principles driving farmers' decisions to help optimize soil building and long-term soil health. This information will help develop recommendations for successful conversion to holistic management to conserve resources, improve profitability and sustainability. Eight participating farms will be located in two Wyoming wheat-production areas: the more arid, low-productivity Slater Bench southeast of Wheatland, and the more mesic, relatively productive Pine Bluffs/Albin area.
Animal Health Component
0%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
The Central High Plains have been largely left out of the "Soil Health Movement" because many of the central principles are not viewed as effective where fallow periods are perceived as necessary for moisture conservation. Dryland agriculture is very important to livelihoods in this region despite the resource-limited and challenging environment. Projections of increased recurrence of drought caused by variable precipitation and extreme winds during fall and early spring mean that the future of agricultural production may be even more challenging. Winter wheat is the primary cash crop even though typical yields are only 20 to 35 bushels per acre. Low biomass yields mean that no-till is not as effective at moisture conservation or SOM accumulation as in other regions, and few farmers practice reduced tillage. A few producers do successfully use no- or reduced-tillage practices, however, and some use cover crops on an opportunistic basis. But the few published research articles suggest that using cover crops in this region negatively impacts crop yields due to competition for water. It is unknown how synergistic effects of reducing tillage and planting cover crops will work in this region and whether one or the other practice should be most recommended.Major Goal: Evaluate whether cover crops, reduction of tillage or a combination of both can be viable practices for dryland crop rotations in the Central High Plains in order to improve soil quality and soil health.Specific objectives:Evaluate integrated cover crops/tillage scenarios on crop yields;Evaluate their effects on soil properties and processes that indicate soil quality, soil moisture, insect populations, and weed competition;Disseminate results to local, regional, and national audiences.Economic analyses are not included but all costs and revenues will be recorded and if these alternative cropping systems show promise a partial budget analysis will be performed.
Project Methods
We propose to utilize long-term antecedent cropping and soil management systems to impose cover crops and see if we can find a suitable combination. Proposed treatments will concentrate on interjecting cover crops by either using them in relay, inter-seeded, or planted after crop harvest to maximize the length of time for the presence of cover crops in the field without any detrimental effects on soil moisture storage much needed for subsequent cash crops.Eight participating farms will be located in two Wyoming wheat-production areas: the more arid, low-productivity Slater Bench south east of Wheatland, and the more mesic, relatively productive Pine Bluffs/ Albin area. Cover crop/tillage treatments will be designed based on location-specific precipitation patterns and soil resource base and will include: (1) spring sown legume or legume/small grain cocktail in place of fallow before wheat planting; (2) relay of spring oat with legume before wheat planting; (3) winter-killed cover crop planted after spring grain or bean crop harvest; and, (4) sunflower companion crop-spring pea grain crop. At least three cover crop treatments will be imposed on each of the existing tillage systems. Treatments will be refined based on focus-group discussions with cooperating and other farmers and other agricultural experts. The experiment will be arranged as randomized split strips with four replications with the antecedent tillage/crop rotation as the main treatment and the cover-crop treatments as split plots one drill-width wide and at least 40 feet long. As is common in this type of on-farm, space-for-time substitution experiment that utilizes long-term management practices, it is necessary to use pseudo-replication of treatments on separate farms. These same fields have been thoroughly characterized for a study of carbon and nitrogen cycling (Norton et al., 2012, SSSAJ 76:505-514).1. Plots will be harvested with a Hegy plot harvester for grain yield and peak standing biomass of cover crops will be harvested by hand each year. Termination of cover crops will be by winter kill, rolling or glyphosate herbicide.2. Soil samples will be collected each year in early June to correspond with peak soil microbial activity and nutrient cycling. Samples will be collected using a 5-cm-diameter core from 0- to 15-cm and 15- to 30-cm depths. Samples will be split and half sent to Ward Lab in Kearney, NE, for determination of the Haney Soil Health Number and soil fertility values. Soil chemical, physical, and biological parameters that determine soil quality and SOM cycling will be determined as follows:Basic soil quality: Basic soil properties will be quantified by standard analysis methods once at the beginning and at the end of the study. Analyses include particle-size distribution by the hydrometer method (once in year 1 only), bulk density by the core method (each year with labile-pool samples), pH and electrical conductivity (EC) by electrode, total cabon (C) and nitrogen (N) by Carlo Erba combustion on an EA1100 Soil C/N analyzer (Carlo Erba Instruments, Milan, Italy), inorganic C by modified pressure-calcimeter, and gravimetric moisture.Labile-pool SOM: To quantify available and readily mineralizable C and N fractions that respond rapidly to management changes, 10-g subsamples will be extracted with 0.5M K2SO4 and analyzed for NO3- and NH4+, dissolved organic C and N. Microbial biomass will be analyzed on fresh, refrigerated soil samples within 72 hours of collection by fumigation-extraction. Mineralizable C and N will be analyzed by 14-day aerobic incubation. These dynamic properties will be measured at peak growth each year.Soil Moisture: Soil moisture will be determined at planting and on a monthly basis from March through August of each wheat crop using a 503 DR Hydroprobe neutron scattering device (CPN International, Concord CA) at 10-, 20-, 30-, 60- 120-, 150 and 180cm depths after installation of two aluminum access tubes per plot in one block.GHG emissions: Will be assessed weekly during the growing season using chamber technique deployed in field. Collected gas samples will be analyzed for nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) using Schimadzu GC-2014 Gas Chromatograph.Macro and micro-invertebrates: two times per year using insect traps deployed in the field.Weed population: once per year using Daubenmire plots.3. A series of regression and correlation analyses among Haney test and soil C and N, GHG and other properties will be developed.