Research

Ongoing Projects:

  • Near-infrared (NIR) spectroscopy as a tool for rapid determination of plant- and soil-responses.
  • Assessment of silvopastoral systems in the Peruvian Amazon (website Silvopastures Peru).
  • Defoliation management effects on cool-season grass-legume mixtures.
  • Utilization of swine effluent and poultry litter as nutrient sources for forage and bioenergy production.

 

Completed Projects:

  • Assessment of silvopastoral systems in Amazonas, Perú and North Carolina, USA

Silvopastures are characterized by the intentional integration and management of trees,  forages, and livestock. They have been broadly accepted as an integrated approach to sustainable land management with potential to provide ecosystem services while providing options to mitigate and adapt to climate change. In the northern Peruvian Amazon  we identified, described, and assessed the most prevalent silvopastoral systems. Raising cattle activities in this region occurs mainly in production units with area < 10 ha. Predominant silvopasture designs consisted of trees in live fences and scattered trees. Understory forage is mainly monoculture grass grazed by dual-purpose cattle breeds. The common denominators of the types of trees utilized in these systems are trees pruned to obtain firewood, followed by timber trees, followed by fruit trees. Specific details of the project can be found here.

In North Carolina, we tested the effects of three tree species (two evergreen and one deciduous) on understory forage productivity  and microclimate. The mitigation potential of trees on temperature, relative humidity, and temperature-humidity index was moderate and it varied as a function of time of the day and month of the year and it was more noticeable during the daytime of summer months. The mitigation potential was at the most 1° for temperature and temperature-humidity index and 3 points for relative humidity. The main feature of the silvopastoral system’s design in NC is the provision of year-round shade by the tree-component, with varying levels of shade due to tree species and season.

A gallery of pictures from both projects can be found here.

Publications: Agroforestry Syst. 94:173-283; Agric. Ecosyst. & Environ.

  • Defoliation management of switchgrass as a forage and bioenergy crop

Switchgrass can be used as a dual-purpose crop, as forage and bioenergy feedstock. Productivity, quality of the harvested herbage, and persistence of switchgrass were investigated as a function of frequency, intensity, and end-of-season defoliation. Intense defoliation regimes such us harvesting every 3 wk to ≥ 40-cm stubble height or every 6 wk to ≥ 20-cm stubble height are possible without compromising persistence of ‘Performer’ switchgrass but such management will result in 50% or greater reduction of dry matter yield compared to harvesting every 9 and 12 wk. Frequent defoliation will also result in greater digestibility and crude protein.   Although there are tradeoffs when managing for productivity or nutritive value, there is a wide range of defoliation management options for switchgrass that provide flexibility in terms of harvesting schedules and to optimize productivity and persistence as a forage or bioenergy feedstock.

Publications: Agron J. 110:1467-1472; Crop Sci. 59:1309-1316; Crop Sci. 60:1682-1689.

  • Nitrogen fertilization rate and swine effluent application effects on bioenergy sorghum production in North Carolina

Dry matter yield and nutrient removal information is critical for the development of nutrient management plans to optimize productivity and environmental conservation goals. Sorghum cultivars ES5200 and M81-E were evaluated for four years in North Carolina in experimental areas located at a research station and also on-farm. Dry matter yield of sorghum ES5200 was greatest at a N fertilization rate of 67 kg per hectare with no significant increase of dry matter yield production beyond this N rate.  There was no N fertilization rate effects for dry matter yield response of sorghum M81-E. Both sorghum cultivars were productive biomass crops at swine spray fields and may be a feasible alternative for producers that desire the flexibility of an annual crop and high biomass yields (~16 Mg per hectare) in a single clipping at the end of the growing season; however, nutrient loadings will need to be less intensive (lower amounts) compared to current bermudagrass-based systems to comply with NC nutrient management plan guidelines.

Publications: Agron. J. 109:1352-1358; Agron. J: 109:2521-2529; CSANews; Agron J, doi:11.2134/agronj2018.0..0178

 

  • Inoculation and silo-type effects on microbiome, fermentation, and aerobic stability of oats and low-moisture corn silage

Silage production and utilization is an important source of forage in the USA (it represented ~44.2% of the total forage harvested in 2014). Understanding the microbial ecology of silages is critical to identify novel microorganisms for optimal silage making and to prevent the growth of pathogens that compromise the animal and food safety chain. We used next-generation sequencing (NGS) to characterize the silage ecology of oats and the use of silo-bags vs. buckets and the ecology of low-moisture corn silage. Inoculation improved whole-crop corn and oat silage quality because of a shift in the bacterial and fungal community composition during ensiling that favored aerobic stability. Both techniques of silo-types are comparable for characterizing the effect of inoculation on the most basic measurements of silage quality.

Publications: J. Dairy Sci. 100:1812-1828; J. Dairy Sci. 101:3057-3076.

 

  • Establishment and defoliation management of a warm-season legume into warm-season grass pasture

We proposed strip-planting as an alternative to establish rhizoma peanut (Arachis glabrata) into existing bahiagrass (Paspalum notatum) pastures with the ultimate goal of achieving a grass-legume mixture. Including legumes in warm-season forage-livestock systems has the potential to increase the nutritive value of the forage offered to livestock and to increase Nitrogen cycling in the system. Control of plant competition (cultural, chemical, and mechanical) and defoliation management (clipping vs. grazing) were more critical factors than seedbed preparation for successful establishment and spread (~30 cm per year) of rhizoma peanut. In addition, if grazing does occur during the first 2 years of planting, grazing management targets for the endpoint of grazing should focus on the strip component of the pasture planted to rhizoma peanut as opposed to the bahiagrass component of the pasture.

Publications: Crop Sci. 53:724-731; Crop Sci. 53:2255-2263; Crop Sci. 54:1868-1875; Crop Sci. 55:2384-2389

 

  • Municipal biosolids an alternative source of nutrients for the production of forages as bioenergy crops

Forages, as all other plants,  require nutrients to grow. The potential to utilize forage plants as bioenergy crops (referred to as lignocellulosic feedstock) and produce greater amounts of biomass provides incentive to look for altenative, local sources of fertilizers. Municipal biosolids, a by-product of waste-water treatment plants, have the potential to provide nutrients for biomass production.  Environmental conditions (temperature and rainfall) and method of application (surface application and incorporation) influence the total amount and the rate of nitrogen available for plant growth.

Publications: Agron. J. 102:1308-1313; Agron. J. 102:1314-1320; Agron. J. 103.899-905

 

  • Land management effects on phosphorus pools in Histosols.

Long-term land management affected the distribution of Phosphorus in soil chemical fractions. Soils under intensive cultivation had a lower proportion (52%) of Phosphorus in the organic fraction compared to non-cultivated (78%). In addition, intensive tillage regime promoted the redistribution of Calcium from subsurface to surface soil, which leads to greater Phosphours sequestration in the Calcium-bound fraction.

Publications: Geoderma. 145:130-135; World J. Agric. Sci. 4:314-320

  • Producción y composición de los cultivares Mulato I y II de Brachiaria híbridos inoculados con Micorriza y Trichoderma harzianum.

Los cultivares Mulato I y II desarrollados por el Centro de Agricultural Tropical (CIAT), fueron evaluados en Honduras, C.A. La produccioón de materia seca fue similar entre cultivares y tratamientos (9.6 Mg ha-1 yr-1). Adicionalmente, digestibilidad de materia seca, fibra neutro- y ácido detergentes fueron similares (60.3%, 50.5, y 29.2%, respectivamente). La concentración de proteína cruda fue mayor en Mulato II (15.2%) comparada con Mulato I (12.6%).

Publicaciones: Ceiba. 47:25-32