W. Ashley HammacGeosmin Agricultural Solutions
W. Ashley Hammac
Doctor of Philosophy
Investigating agricultural solutions that improve resiliency in agroecosystems and the farm economy.
About
26
Publications
5,386
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179
Citations
Introduction
The objective of my research is to develop efficient and sustainable conservation cropping systems utilizing diverse crop rotation, minimum tillage or no-till, nutrient/manure management and cover crops that maximize farm profit and ecosystem services.
Additional affiliations
September 2020 - present
Ward Laboratories
Position
- Soil and Agronomic Specialist
August 2018 - September 2019
Solum Laboratory
Position
- Researcher
April 2018 - August 2018
Purdue University
Position
- PostDoc Position
Education
August 2007 - December 2015
August 2002 - May 2005
August 1995 - May 2001
Publications
Publications (26)
There is disagreement about the potential for regenerative management practices to sequester sufficient soil organic carbon (SOC) to help mitigate climate change. Measuring change in SOC stocks following practice adoption at the grain of farm fields, within the extent of regional agriculture, could help resolve this disagreement. Yet sampling deman...
Much attention has been paid to the effects of multiple soil conservation and soil health practices on the mean yield of the subsequent crop. Much less research has focused on the variability of crop yields over time or space. Yield stability reported in standard deviation, mean absolute deviation, or coefficient of variation can be an important me...
Location Cover crops and no-till are two conservation cropping systems practices that are thought to improve soil health. The goals of this study were to determine how cover crops and no-till affect grain yield and yield stability which are critical factors in quantifying resiliency. Plots were initiated as a corn-soybean rotation (C-S) with half a...
Aristotle's successor, Theophrastus, once wrote "annus fructum fert, non tellus" or "the harvest is the year's and not the field's". While we do acknowledge the contribution of soil fertility and crop management, we also understand that year to year variation in environmental stresses (canopy temperature and soil water) are major causes of reductio...
Interactive effects of weather and soil nutrient status often control crop productivity. An experiment was conducted to determine effects of N and S fertilizer rate, soil water, and atmospheric temperature on canola fatty acid (FA), total oil, protein and grain yield. Nitrogen and S were assessed in a 4-yr study with two locations, five N rates and...
Canola is a new crop for many inland Pacific Northwest U.S. wheat growers to consider for integration into their wheat-dominated systems. Both crops have winter and spring varieties that can fill niches in different precipitation zones across the region, and they both efficiently extract available water to depths of 4 to 6 ft if soil depth allows....
EQCom is a simulation game for teaching the effects of conventional farming on natural resources and the social challenges involved in implementing solutions. Players are “farmers” who make a series of choices about farming practices, either conservation or conventional. Outcomes result based on those choices and they include aesthetic and economic...
Core Ideas
Soil quality scores were highest in perennial grass systems, followed by a soybean‐dominated rotation, followed by a corn‐based rotation.
No‐till crop production had no higher soil quality score than chisel–disk tillage but the uncultivated perennial grass system scored higher than both.
In this crop production‐dominated region, soil qua...
Cover crops and crop rotation are two conservation cropping systems practices that are thought to improve soil health. The goals of this study were to determine how cover crops affect soil biological activity (C, N, and enzyme activity) which are critical indicators in quantifying soil health.
Nitrogen fertilizer requirements for economic optimization of spring canola ( Brassica napus L.) production in eastern Washington varies with yield potential. Recent research has revealed that more N is needed per unit of grain (UNR) as yield potential decreases. Because UNR is the inverse of N use efficiency (NUE) at optimal yield, the implication...
Prospects for canola (Brassica napus L.), as a rotational crop for agronomic and market diversification, have stimulated agronomic research to fit this crop into the unique environments and soils where wheat (Triticum aestivum L.) production dominates. The objectives of the present study were to define N and water requirements of canola following w...
Expansion of biofuel cropping systems requires better spatial resolution of life cycle greenhouse gas (GHG) emissions and mitigation potentials. Simulation modeling was carried out to understand the impact of agro-ecological zone (AEZ), and nitrogen (N) use efficiency (NUE) for inland Pacific Northwest canola and Midwestern soybean biodiesel GHG mi...
Prospects for canola ( Brassica napus L.), as a rotational crop for agronomic and market diversification, have stimulated agronomic research to fit this crop into the unique environments and soils where wheat ( Triticum aestivum L.) production dominates. The objectives of the present study were to define N and water requirements of canola following...
Nutrient cycling is an important matter in all crop production but it is particularly important in oilseed production. The efficiency by which oilseed crops can be grown and the impact of their cultivation dictates the future of bioenergy policy. The dissertation that follows attempts to dissect the intricacies of nutrient cycling in Pacific Northw...
The Conservation Cropping Systems Initiative (CCSI) is a partnership between numerous organizations in Indiana all working toward improving soil health and soil productivity. CCSI aims to increase adoption of conservation practices like cover crops, no-till, precision nutrient management, and integrated pest management by 1) building and strengthen...
The purpose of this guide is to summarize current information on canola growth and fertilizer requirements. Canola is a relatively new crop to the Pacific Northwest and little fertility research has been conducted in this region. The information contained in this guide is intended to serve as a reference until the results of ongoing, local research...
Since nitrogen (N) and sulfur (S) are major components of protein and the enzyme complexes acetyl-CoA carboxylase and fatty acid synthase are responsible for oil or fatty acid biosynthesis, it is expected that soil and fertilizer N and S will affect canola grain protein content, fatty acid content, and fatty acid profile (Somerville et al., 2000)....
Since nitrogen (N) and sulfur (S) are major components of protein and the enzyme complexes acetyl-CoA carboxylase and fatty acid synthase are responsible for oil or fatty acid biosynthesis, it is expected that soil and fertilizer N and S will affect canola grain protein content, fatty acid content, and fatty acid profile (Somerville et al., 2000)....
An imaging method was developed to evaluate crop species differences in root hair morphology using high resolution scanners,
and to determine if the method could also detect root hair responses to soil water availability. High resolution (1890 picture
elements (pixels) cm−1) desktop scanners were buried in containers filled with soil to characteriz...
Understanding crop root morphology will enable better understanding of nutrient uptake efficiency and ultimately improve crop management. The ability to observe the rhizosphere with high resolution scanners will allow characterization of root-soil interactions in real-time. High resolution (4800 dpi) desktop scanners were buried in containers fille...
In the dryland agriculture areas of the Pacific Northwest, where wheat (Triticum aestivum) cultivation dominates, farmers have few rotational crops at their disposal. Oilseed producing crops, along with serving as biodiesel feedstock, may also serve as alternative rotational crops. Understanding the root structures and their respective rhizospheres...
Improved methods for broiler chicken (Gallus gallus domesticus) litter utilization are needed to alleviate potential impacts of pollution around broiler production operations. Pelletization may constitute one improved method for handling broiler litter. The objective of this study was to determine the change in nutrient concentration from pelletizi...
Questions
Questions (3)
There is a growing interest in developing means of early detection of crop nutrient deficiencies. It has held that by the time a deficiency shows up in a soil sample, the crop is already under stress. Does crop sap analysis help to resolve this information gap? If so, how can we expand the use of this from high margin specialty crops to commodity crops?
In many areas, conversion from conventional production practices to conservation practices (minimum tillage, cover crops, crop rotation/diversity, manure/livestock addition) results in an immediate benefit to both crop yield and yield stability over space and time. It is my expectation that land areas that would have an immediate benefit would have soils that are highly erodible, course textured, and/or inherently low fertility. Conversely, I expect that high fertility soils may experience a more delayed benefit from conversion to conservation practices. This concept, combined with other factors, I believe, are responsible for the low adoption rates for conservation practices throughout the midwestern United States. Although soil loss in this region is greater than the sustainable replacement rate. Some research, including my own (An Analysis of Yield Variation Under Soil Conservation Practices), has taken on this challenge by relating conservation practices to yield stability through space and time. The goal is to establish that if yields are more stable under conservation systems, crop insurance premiums should reflect that reduction in risk, similar to the way a healthy lifestyle results in a lower health or life insurance premium. This incentive by reduced crop insurance may better drive adoption of conservation practices and preserve the resource. This is meant to open a discussion on the topic for students, researchers, policy makers, etc. to explore this idea. Please share your thoughts on this topic. Cheers!
I am wondering how agricultural economist consider land (price or value) when calculating operating costs for farmers. Since some farmers own all of their land (own outright and have no payments) , some are buying or rent all of their land, and some (probably most in the U.S.) own outright and rent or are purchasing. I am considering this from the standpoint of the economics of implementing conservation practices (e.g. cover crops and manure management). So if a farmer has no payments on all of their land, they would have much more room in their budget to implement conservation practices. Whereas a farmer who rents or is buying all of theirs would not have that flexibility in their budget. I'm just wondering if there is a standard assumption that ag economists use.
