About

Dr. Miguel Castillo is an Associate Professor in the Department of Crop and Soil Sciences at North Carolina State University, where he leads the Forage and Grassland Program. His research focuses on enhancing ecosystem services in agricultural and pasture-based livestock systems, including agroforestry and silvopastures. His work emphasizes developing knowledge and technologies that promote efficient resource use and system resilience, with key areas including alternative nutrient sources such as biosolids, poultry litter, and swine effluent, forage and grazing management, use of legumes, integrated crop–livestock systems, and the application of near-infrared spectroscopy as a decision-support tool. Originally from Loja, Ecuador, Dr. Castillo earned a B.S. in Plant and Animal Sciences from Zamorano University in Honduras, and both M.S. and Ph.D. degrees in Agronomy from the University of Florida. He also holds an MBA from North Carolina State University. Since joining NC State in 2013, he has contributed to the discipline through research, extension, and as a Technical Editor for Crop Science. His program maintains an active international presence, with work spanning tropical, subtropical, and temperate regions. Dr. Castillo is fluent in Spanish and English and has intermediate proficiency in Portuguese.

Research topics

• Geography
• Agronomy
• Ecology
• Forestry
• Biology
• Environmental science
• Agroforestry
• Economics
• Chemistry
• Business
• Chromatography
• Agricultural economics
• Finance
• Agricultural science
• Materials science

Selected publications

• Late‐summer nitrogen fertilization rate effects on herbage mass, nutritive value, and fertilizer recovery efficiency of stockpiled bermudagrass

  Crop Science · 2026-04-29

  articleOpen access

  Abstract Stockpiled bermudagrass ( Cynodon dactylon (L.) Pers.) can potentially provide nutritious forage and extend the grazing season in the upper southeastern US Coastal Plain. This multi‐location 1‐year study evaluated the effects of four N fertilizer rates (from 0 to 135 kg ha − 1 ) and four harvest dates (from October to January) on leaf‐to‐stem ratio, herbage mass (HM), crude protein (CP), in vitro organic matter digestibility (IVOMD), nitrate‐N, N removal, and fertilizer N recovery efficiency (FNRE) of stockpiled bermudagrass. Stockpiling began in mid‐August at seven on‐farm sites encompassing seven soil series and four bermudagrass cultivars (Coastal, Midland 99, Ozark, and Tifton 44). Leaves had greater CP and IVOMD than stems. The leaf‐to‐stem ratio declined from 1.0 in October to 0.6 in January. Forage nutritive value decreased over time, with CP declining from 115 to 76 g kg −1 and IVOMD from 490 to 319 g kg −1 between October and January. Averaged across harvests, CP increased from 84 to 100 g kg −1 as N rates increased, whereas IVOMD (408 g kg − 1 ) was unaffected by N rate. The HM increased with N fertilization, ranging from 1385 to 2539 kg ha − 1 in October and from 1069 to 1670 in January. Nitrogen removal ranged from 12 to 51 kg ha − 1 and FNRE ranged from 31% to 9%, with greater values observed in October at lower N rates. Overall, late‐summer N fertilization increased HM and CP without exceeding nitrate toxicity thresholds; however, the low digestibility values indicate that energy supplementation would be required for weaned calves and dry mature cows.

  PublisherDOI

• Reporting forage nutritive value using near‐infrared reflectance spectroscopy

  Crop Science · 2025-04-24 · 4 citations

  articleOpen access1st authorCorresponding

  Abstract Despite the well‐documented merits of near‐infrared reflectance (NIR) spectroscopy for forage nutritive value analysis, recent studies reveal inconsistencies in accuracy of NIR‐predicted values. These findings underscore the critical need for robust validation efforts to ensure reliability. Employing visual tools, such as scatter plots comparing laboratory‐measured with NIR‐predicted values, enhances the interpretation and qualification of data. Standardized reporting of validation outcomes, including key metrics and best practices, is essential for ensuring data quality and fostering broader adoption of NIR spectroscopy across research and industry. In this article, we suggest guidelines for reporting NIR spectroscopy predictions and emphasize the need for independent validation as a required procedure to enhance the credibility and application of NIR spectroscopy for forage analysis.

  PublisherOA PDFDOI

• Performance evaluation of two handheld NIR spectrometers to determine forage nutritive value using custom calibrations

  Crop Forage & Turfgrass Management · 2025-10-26

  articleOpen access1st authorCorresponding

  Abstract Recent technological advancements have led to the release of several commercially available near‐infrared (NIR) solutions, especially with handheld portable spectrometers. We define a NIR solution as the integration of hardware, software, and standardized operating protocols for handling and scanning samples. Rather than relying solely on pre‐loaded calibrations, which may not always meet accuracy requirements or be available for a specific application, NIR users can benefit from being able to develop custom calibrations. We hypothesized that, despite inherent differences in spectra and scanning protocols, custom calibrations developed using a single software pipeline could yield comparable performance across different NIR solutions. Spectra from 317 dried–ground forage samples (grass–legume mixtures) were collected using two portable handheld spectrometers (Trinamix and NeoSpectra) and used to develop NIR models to predict forage nutritive value (crude protein and in vitro organic matter digestibility). During the scanning process, the samples were in direct contact with the Trinamix spectrometer, whereas for the NeoSpectra spectrometer, scanning was performed through a sampling container. Despite differences in the spectra, NIR‐predicted values closely aligned with the laboratory reference values, showing a strong model fit for both NIR solutions. All models achieved r 2 values ≥0.90, with bias ranging from –0.22% to –0.17% and SE of prediction (SEP) ranging from 1.8% to 2.3%. Different model parameterization was needed to optimize the performance of each NIR solution. Our findings demonstrate that flexible software can support the development of custom NIR models, paving the way for tailored, user‐defined NIR solutions.

  PublisherOA PDFDOI

• Risk of weed seed and seedling emergence from poultry litter

  Agrosystems Geosciences & Environment · 2024-02-29

  articleOpen access

  Abstract In areas surrounding large poultry industries, poultry litter is often an alternative nitrogen fertilizer for crop production. However, farmers who have not used poultry litter in the past have concerns regarding potential weed seed contamination. A survey was conducted to determine the occurrence of germinable weed seed in poultry litters ( n = 61) submitted by growers and industry representatives across North Carolina. In a 9:1 potting media:poultry litter mix, a single grass seed germinated from the 61 surveyed poultry litters, equating to 0.3 viable seeds 100 g −1 poultry litter. Viable seed content averaged 1.1 seeds 100 g −1 litter using the extractable seedbank method on 25% of the litters from the survey, much higher than the grow out method, and the majority of seeds found were Amaranthaceae . A growth chamber experiment was then conducted and demonstrated that there was a negative relation between poultry litter application and weed seedling emergence. There was a 65%, 75%, and 85% reduction in Senna obtusifolia (L.) H.S. Irwin & Barneby , Setaria pumila (Poir.) Roem. & Schult., and Amaranthus palmeri S. Watson germination, respectively, from the control to highest application rate of poultry litter (26.9 Mg ha −1 ). A laboratory study showed that poultry litter leachates can decrease seed radicle length and integrity and is likely due to osmotic or salinity stress. The weed seed content in litter as well as the negative impact of poultry litter and its leachates on weed seedling emergence make it unlikely that poultry litter applications will significantly increase seedbanks above levels commonly observed in agricultural fields.

  PublisherOA PDFDOI

• Development of Silvopastoral Systems in the Peruvian Amazon

  2023-01-01 · 4 citations

  book-chapter
  PublisherDOI

• 114 Evaluation of Assertions from Educational, Outreach and Engagement Programs in Pasture-Based Livestock Systems

  Journal of Animal Science · 2023-05-01

  articleOpen access1st authorCorresponding

  Abstract Assertions about grazing management and grazing systems should be evaluated based on the scientific literature. Prior assumptions can limit our ability to achieve constructive dialogue regarding the merits of various stocking methods. These include the assumption that rotational stocking is inherently superior to continuous stocking, regardless of the nature of the overall grazing system, and the presumption that continuous stocking implies overgrazing. We revisited assertions about grazing management in general, but more specifically the choice of the stocking method, and considered their merit in the context of evidence from the literature, including a chapter titled Prescribed Grazing on Pasturelands from a National Resource Conservation Service (NRCS) literature synthesis published in 2012. We framed those assertions in the form of questions. The questions were: a) Does choice of rotational stocking ensure well-managed pastures?, b) Does rotational stocking result in greater accumulation of soil carbon than continuous stocking?, c) Does rotational stocking increase pasture productivity and optimal stocking rate compared with continuous stocking?, d) Does forage nutritive value and individual animal performance increase in rotational versus continuous stocking?, and e) Do pastures “look better” in rotational versus continuous stocking?. The objectives were to consider whether these often-stated assertions about grazing management were supported, refuted, or simply not adequately assessed by the body of scientific evidence. It is important to recognize that choice of stocking method is only one element of grazing management and grazing management is only one element of a grazing system. Thus, stocking method is “one piece of a very large pie”. Additionally, stocking rate (grazing intensity) is a separate and independent grazing management choice from stocking method, such that both rotationally and continuously stocked pastures can be understocked, overstocked, or optimally stocked. It is unfortunate that choice of stocking method dominates discussions of improving grazing management to the expense of other issues, when in fact intensity of grazing has been shown conclusively to be the most important determinant of a wide array of soil, plant, animal, and ecosystem responses. We have observed that terminology such us regenerative grazing, holistic planned grazing, adaptative multipaddock grazing, management intensive grazing, high intensity low frequency grazing, and others, arise frequently and can dominate discussions in the realm of education, outreach and engagement programs in pasture-based livestock systems. These words/themes lack clear definition, and this lack of specificity may promote misconceptions, thus hindering the opportunity for critical thinking and ultimately the advancement and improvement of grazing systems. Educational efforts in pasture management should strive to remain relevant by focusing on experimental evidence. Local (i.e., state or county level) outreach and engagement programs are challenged with providing timely and specific information with implementable guidelines based on frequent observations at the landscape and farm levels.

  PublisherOA PDFDOI

• Analysis of alkaloids and reducing sugars in processed and unprocessed tobacco leaves using a handheld near infrared spectrometer

  Journal of Near Infrared Spectroscopy · 2023-01-16 · 4 citations

  article1st authorCorresponding

  Near infrared (NIR) spectroscopy calibration models were developed to predict chemical properties of flue-cured tobacco ( Nicotiana tabacum L.) leaf samples using a microPHAZIR TM handheld NIR spectrometer. The sample data set consisted of 348 leaf-bundled samples of upper-stalk flue-cured tobacco leaves collected from an array of cultivars evaluated in multiple locations. Unprocessed leaf samples were intact whole unground leaves collected from curing barns. Processed leaf samples were further dried and ground before scanning. The NIR prediction models for percent reducing sugars, percent total alkaloids, and percent nicotine were very good for processed leaves [r 2 (SEP in %) values = 0.98 (0.82), 0.92 (0.17), and 0.92 (0.14), respectively]. The models for the same three variables for unprocessed leaves were also very good, with only slightly lower fit statistics [r 2 (SEP) = 0.93 (1.58), 0.87 (0.22), and 0.88 (0.18), respectively). Fit statistics for anabasine NIR models were intermediate with r 2 (SEP in %) values ranging from 0.73 (0.003) to 0.76 (0.003), while the lowest fit statistics were observed for anatabine and norticotine with r 2 (SEP in %) ranging from 0.49 (0.005) to 0.55 (0.017), respectively, for both unprocessed and processed leaves. Hence, use of a handheld NIR spectrometer would be of more limited value for these variables. The chemical composition of flue-cured tobacco leaf samples for some chemical traits can be directly assessed at the point when the leaves exit the curing barns, thus minimizing the need to dry and grind samples for colorimetric and chromatographic analyses.

  PublisherDOI

• ‘Newell’ bermudagrass: A public release from the USDA <i>Cynodon</i> collection

  Journal of Plant Registrations · 2023-08-30 · 8 citations

  article

  Abstract Warm‐season perennial grasses are the backbone of the pasture‐based livestock industry in the lower southeastern United States, and bermudagrass ( Cynodon spp.) is the most widely planted forage species, covering ∼15 million ha. The genus Cynodon is native to southern Africa, and germplasm collections possess high genetic and phenotypic variability. The USDA National Plant Germplasm System maintains a collection of bermudagrass plant introductions (PIs) in Griffin, GA, and USDA‐ARS, Tifton, GA, maintains additional germplasm. Multi‐location trials were established in four states (Florida, Georgia, North Carolina, and Oklahoma) to screen Cynodon germplasm for herbage accumulation (HA), nutritive value (NV), and bermudagrass stem maggot (BSM) ( Atherigona reversura Villeneuve). Due to the large genotype × environment interaction for HA, we focused on selecting accessions adapted to South Georgia and Florida, and further studies were performed in Florida. Several PIs showed improved HA and NV compared with ‘Tifton 85’. PI 316510, originally introduced from Ingelheim, Germany, produced high HA in Citra, FL, and Tifton, GA, with improved NV traits. In addition, PI 316510 had faster establishment and similar BSM tolerance to Tifton 85. We confirmed PI 316510 as tetraploid (2 n = 4 x = 36) through chromosome counts and flow cytometry, and it is genetically distinct from other commercial cultivars. PI 316510 has been publicly released under the name ‘Newell’, and it is vegetatively propagated. Planting material can be requested from the UF‐IFAS Forage Breeding program.

  PublisherDOI

• Poultry litter and nitrogen fertilizer effects on productivity and nutritive value of crabgrass

  Crop Science · 2022-09-07 · 13 citations

  articleOpen accessCorresponding

  Abstract Crabgrass ( Digitaria spp.) is deemed as a productive and nutritious warm‐season annual forage for livestock in the U.S. transition zone. However, there is limited information about nitrogen (N) source and rate effects on productivity and nutritive value of crabgrass in North Carolina. Herbage accumulation (HA), N removal, crude protein (CP), total digestible nutrients (TDN), and tissue nitrate (NO 3 − ) concentrations were evaluated for 2 yr (2020 and 2021) in two physiographic regions (Piedmont and Coastal Plain). Treatments were five rates of chemical N fertilizer (up to 480 kg N ha −1 ), five rates of plant‐available N from broiler poultry litter (up to 472 and 399 kg N ha −1 in 2020 and 2021, respectively), and one control (zero N). Overall crabgrass responses were not different between N sources. At Coastal Plain, HA increased from 4,990 kg dry matter (DM) ha −1 and plateaued at 7,136 kg DM ha −1 at an agronomic optimum N rate (AONR) of 198 (SE = 49) kg N ha −1 . At Piedmont, HA responses were erratic, estimation of an AONR was not possible, and HA values were approximately half or less to those at Coastal Plain. Removal of N was linearly associated with HA. Increasing N rate had a marginal positive effect on CP (ranged from 126 to 154 g kg −1 ) and no effect on TDN (averaged 626 g kg −1 ). Tissue NO 3 − values were below the toxic threshold for feeding livestock. Poultry litter is an effective N source for crabgrass. Nitrogen rate effects were more apparent on crabgrass’ productivity; nutritive value was generally high regardless of N rate and source.

  PublisherDOI

• Stocking method and terminology in grazing management: Evaluation of assertions from educational, outreach, and engagement programs

  Crop Science · 2022-11-24 · 8 citations

  article1st authorCorresponding

  Abstract We revisited terminology and assertions about grazing management in general, but more specifically the choice of the stocking method, and considered their merit in the context of evidence from the literature, including a chapter entitled Prescribed Grazing on Pasturelands from a National Resource Conservation Service (NRCS) literature synthesis published in 2012 (Nelson, 2012). We framed those assertions in the form of questions. Our objectives were to consider whether these often‐stated assertions about grazing management were supported, refuted, or simply not adequately assessed by the body of scientific evidence and to help focus future discussion about the topic.

  PublisherDOI

Frequent coauthors

• J.J. Romero

  University of Maine

  12 shared

• Lynn E. Sollenberger

  University of Florida

  11 shared

• Praveen Kolar

  North Carolina State University

  8 shared

• Sanjay B. Shah

  8 shared

• Lingjuan Wang-Li

  8 shared

• Eduardo Gutiérrez‐Rodríguez

  Colorado State University

  7 shared

• J. M. B. Vendramini

  University of Florida

  7 shared

• Ann R. Blount

  Southwest Florida Research

  7 shared

Labs

• Crop and Soil SciencesPI

Education

• Ph.D., Crop and Soil Sciences

  North Carolina State University

  2005

• M.S., Crop and Soil Sciences

  North Carolina State University

  2001

• B.S., Agricultural Education

  North Carolina State University

  1998