Soil Health Assessment, Management, and Training: Vegetable Production Systems

Development of Tier I soil health assessment protocol: One of the project performance targets was to identify soil health indicators that were most useful for adoption as part of routine soil health testing. Initially, forty soil physical, biological and chemical indicators were measured in the field and laboratory to evaluate them as potential soil health indicators (Appendix E - a complete list of indicators). The chemical properties are those associated with the standard soil test, while the physical and biological properties are newly-established or existing methodologies that allow for fairly rapid soil testing. As described in the materials and methods, soil samples collected from replicated research sites, on-farm grower demonstration trials and commercial farm fields across New York State were used to evaluate the selected indicators. All the data collected from the sample identification sheets and the measured indicators was compiled into a soil health database. The five criteria used for the selection of the indicators used in the Tier I soil health assessment were: 1) sensitivity to changes in soil management; 2) relevance to soil function and crop production; 3) results obtained were consistent and reproducible; 4) ease and time of sampling; and 5) cost (materials and time) of field and laboratory analysis. Based on these criteria, we developed a Tier I soil health assessment protocol for New York soils. Tier I consists of indicators that can be measured or estimated rapidly and are relatively inexpensive to process. Tier I relies on sampling methods that are similar to those used for standard chemical testing and are discussed in detail later in the report. The selected Tier I soil health assessment indicators include bulk density, wet aggregate stability, available water capacity, field measured penetration resistance to assess surface and subsurface hardness, potentially mineralizable nitrogen, active carbon, organic matter, root health measurement, and the standard soil chemical measurements (available phosphorus, exchangeable potassium and magnesium, pH, magnesium, iron, manganese, and zinc). Soil sampling and development of centralized soil sample analysis: Developing a soil sampling protocol that met the requirements of all measured indicators was a challenge. Sampling for the initial set of 40 indicators required the collection of both disturbed and undisturbed (250 cc capped metal rings) soil samples. Although the information collected from the undisturbed cores (pore size distribution, bulk density, soil respiration, etc.) was important, the logistics and practicality of distributing and collecting that type of sample made it not time or cost-effective to include for the basic soil health assessment measurements. In order to assess bulk density and other selected physical indicators for which a known volume of soil is required, it was determined that undisturbed core samples pushed into a small bag (now, a disturbed core sample) could be used for assessment. All other soil chemical and biological indicators are assessed from a bulk soil sample collected into a larger bag. Initially replicate soil samples were taken from each field, a practice that is still encouraged, but it is not cost-effective for routine assessment. It is recommended that the field to be sampled is sub-divided (or not) based on soil type, topography and management practices similar to a nutrient analysis sample. At each of four locations (sampling stations) in the field, one disturbed core sample is taken and pushed into a small bag labeled with field identification, three bulk soil samples are taken and placed in a larger bag also labeled, and the penetrometer resistance measurements are taken at the 0-6, 6-12 and 12-18 inch depths in three locations and recorded on the grower data form. The smaller bag (containing a total of four disturbed cores) is placed in the larger bag (containing a total of 12 bulk soil samples) that make one complete soil health sample per field (see Appendix F for more detailed instructions). The timing of sampling (early spring/ pre-land preparation, mid-season, after harvest) did have a significant effect on soil indicator measurements and therefore the interpretation of the results and management recommendations. To reduce variability, standardize the protocol, and reduce costs, a one-time sampling in early spring prior to land preparation and planting is recommended. This also enables growers to use the included nutrient analysis report to make current season nutrient management decisions. Initially upon collection, soil samples were divided between four separate labs for analysis, one lab measured the physical indicators, two the biological indicators, and a portion of the sample was sent to the Cornell Nutrient Analysis Lab for standard chemical analysis. As the number of samples collected increased, the logistics of sample identification, assessment and data management became a growing challenge. Once the Tier I assessment indicators were selected, the lab procedures, data entry and report generation were centralized in one location to expedite sample processing. Development of the Tier I soil health assessment report and suggested management options: The raw data from the individual indicators and background information about the sample locations was synthesized into the developed auto-generated and grower-friendly report. The standard soil health test report presents soil health information for a given field in a way that enables growers to identify areas where to target their management efforts. From our research, we found that the textural differences in the surface soil have significant impact on the interpretation of soil health measurements. We therefore developed a soil health test report template based on the three major textural classification of the soil (sand, silt and clay). The soil health test report is presented on a single page and consists of different sections laid out in a visually enhanced format to present information to the growers (Appendix G). The sections of the report include: 1) Information section: The information collected during sampling is presented in this section. This information includes the farm name and contact information, the sample number, the date of sampling, the local extension educator, both current crop and tillage and their history over the past 2 years, drainage and slope conditions, soil type and soil texture. 2) Indicator list: This section gives a list of indicators that were measured for soil health assessment. They are color coded to separate the physical, biological and chemical indicators. 3) Indicator values: This presents the raw values of the indicators that were measured either in the laboratory or field. 4) Rating: This section presents the scores and color coded ratings of the soil quality indicators. The indicators are scored on a scale of 1-10 based on scoring functions developed for individual indicators. In addition, the indicators are rated with color codes depending on their scores. Generally, a score of less than 3 is regarded as low and receives a red color code. A score from 3-8 is considered medium and is color coded as yellow. A score value higher than 8 is regarded as high and color coded as green. 5) Constraint: If the rating of a particular indicator is poor/ low (red color code), the respective soil health constraints will be highlighted in this section. This is a very useful tool for the growers in identifying areas to target their management efforts. 6) Percentile: This section is presented as a sliding horizontal bar indicating the percentile rating of the indicator values of the soil sample relative to accumulated values in our database for the particular indicator. For example, a score of 75 percentile means that the indicator value of the sample is equal to or greater than 75% of the values recorded for that indicator among the total samples processed from New York and included in the soil health database. 7) Overall quality score: An overall quality score is also computed from the individual indicator scores. This score is further rated as follows: less than 50 is regarded as low, 50-79 is regarded as medium and greater than 79 is regarded as high. The highest quality score is 100 and least score is 10, thus it is a relative overall soil health status indicator. Based on reports in the literature and research conducted by Cornell Soil Health Team members, we have compiled a list of both short and long-term management options to address the specific constraints identified by the Tier I soil health assessment protocol. For example, to address the constraint of low aggregate stability, in the short-term the integration of shallow-rooted cover or sod-rotational crops and use of manure is recommended to help stimulate soil microbial activity that indirectly improves soil aggregation. In the long-term reducing tillage intensity is recommended. The soil constraints identified using the Tier I assessment protocol and corresponding suggested management recommendations are listed in Appendix H. Overall assessment of soil health on sampled vegetable fields in New York State: Using our newly developed soil health protocol, we assessed the status of soil health on vegetable fields in New York. The results of the rating of indicators for 84 vegetable fields are presented in Appendix I. Most of the indicators showing poor quality on many of these fields were the physical and biological indicators. The physical indicators seemed to be the most affected. Over 50% of the fields assessed had low soil aggregate stability, high bulk density and high subsurface hardness. Over 40% of the fields assessed had low available water capacity. Soil physical processes affected by these indicators include aeration, infiltration, shallow rooting, crusting, and water retention. Over 40% of the fields assessed had low organic matter, active carbon and potentially mineralizable nitrogen. Soil processes affected by these include energy and carbon storage, water and nutrient retention, organic material to support biological functions, and nitrogen supply capacity of the soil. The root health conditions for the assessed field were in the medium to good range, probably mainly due to the good rotations employed. Most of the fields have good to medium values for soil chemical indicators except for extractable phosphorus where 20% of the fields assessed had either too low or too high phosphorus. From this assessment it appears that many of the fields have undergone physical and biological degradation as suggested by the limiting values of the soil health indicators measured. This degradation undoubtedly is limiting optimal growth and yield of vegetable crops grown in NY soils. Outreach activities: One of the primary objectives (and subject of several milestones) of this project was to increase the soil health literacy among vegetable growers, extension educators and other agricultural service providers. Our team has devoted considerable time and effort to provide extensive and varied outreach activities that we believe have greatly increased the soil health literacy among stakeholders throughout New York and the Northeast region. The team held a large number of field days and twilight meetings (>24 in NYS) to discuss soil health constraints, view trials that were being conducted at the site, and demonstrate selected soil health field measurements. Also, the team has organized and presented annual soil health sessions at the NYS Fruit and Vegetable EXPO that have been well attended (100-150 people annually). In addition, the team held three soil health workshops attended by extension educators, consultants, NRCS personnel and other agricultural service providers during 2005 and 2006 (about 80 attendees). Furthermore, we have written a large number of articles in extension publications and several of our team members have made presentations at grower and professional society meetings held regional, nationally and/or internationally. See Appendix J for a list of soil health outreach activities. A soil health website (http://www.hort.cornell.edu/soilhealth) was established in 2003. It continues to be an important source of information on soil health and soil health related issues in addition to information on the research and outreach efforts of this project. It contains a calendar of upcoming events as well as soil health related presentations made at various grower and professional meetings. The website is in the progress of being reorganized to make the results of this research project more readily accessible to the end-users. The primary “buttons” will include Cornell’s Soil Health Team, the soil health manual, a photo gallery, about soil health, measuring soil health and links/ other resources. A soil health manual is in the latter stages of development and is anticipated to be in print in February 2007. The objectives of the manual are to: 1) provide an overview of the concept of soil health; 2) describe soil constraints and soil quality issues common to soils in New York and the Northeast region; 3) provide guidelines about how to conduct in-field soil health assessment; 4) provide a how-to guide for sampling and analyzing soils to assess for soil health; 5) provide an overview of methods used to assess the health status of soil; 6) identify management options for improving soil health based on the constraints detected; and 7) increase awareness of and literacy on soil health issues.