Effects of Biochar on Soil Nutrient Retention and Microbial Communities in Vegetable Cropping Systems

Project Overview

Project Type: Graduate Student
Funds awarded in 2013: $9,367.00
Projected End Date: 12/31/2013
Grant Recipient: Iowa State University
Region: North Central
State: Iowa
Graduate Student:
Faculty Advisor:
Dr. Ajay Nair
Department of Horticulture, Iowa State University


  • Vegetables: carrots, peppers


  • Education and Training: demonstration, on-farm/ranch research
  • Natural Resources/Environment: carbon sequestration
  • Soil Management: soil microbiology, soil quality/health


    Field experiments investigating the fitness of biochar as a soil amendment in vegetable cropping systems were carried out in 2012 and 2013 at the Iowa State University Horticulture Research Station in Gilbert Iowa.  Biochar was added at four rates (0.0, 1.1, 2.2 and 4.5 kg.m-2) to two plots both a loam and sand soil. Biochar did not have an effect on yields of marketable fruit in either soil. Biochar did however reduce yields of unmarketable fruit especially fruit with blossom end rot and sun scald. Biochar also affected soil nitrogen in soil tests, as well as nitrates in the leachate samples taken throughout the season. However, these differences were not consistent between soil types or years.


    In the Midwest many new farmers are turning to vegetable production on small acreages. This trend is in large part due to high land and equipment prices, associated with modern row crop farming, as well as an increase demand for local foods by consumers. This increase interest in producing vegetables on small acreages has even been recognized by organizations like SARE and National Center for Appropriate Technology (NCAT). In fact, much NCAT literature is aimed at educating and preparing beginning farmer to be profitable while maintaining and/or improving their soils and land. The NCAT also recognizes that these new farmers range in age from young adults just starting out to retirees looking for a post retirement career. These new farmer also have various levels of experience and expertise. One trait these farms often share is they are quick to adopt new ideas and technologies as they come out. One such technology that is gaining interest among small farmers includes the use of carbon as a soil amendment. This soil amendment is referred to as biochar. Ideally biochar would be sourced locally from the byproducts of biomass that has been processed using pyrolysis to extract biofuels and energy. Pyrolysis is the process of thermally decomposing biomass in a low oxygen environment. Pyrolysis yields bio-oils, syngas, and heat, as well as black carbon (Bridgwater, 2003).

    A search on the internet will return many self-proclaimed experts touting biochar as a benefit to both the environment and plant growth. Many laboratory trials have indeed shown possible benefits with the addition of biochar in temperate soils.  There is, however, little evidence that these benefits carry over to field trials (Jones et al., 2012).  In fact, there is evidence to indicate high levels of biochar may actually reduce plant growth because of changes in nutrient availability (Mikan & Abrams, 1996).  Many of the field studies showing benefits with additions of biochar have been performed in poor tropical soils and soils with otherwise low productivity (Atkinson et al., 2010).  It is therefore important that research into biochar’s effects on plants and soils must consider possible differences between locations and soil types.  Atkinson et al. (2010) noted that soils with differing physical and chemical properties will likely react differently to additions of biochar.  They also conclude that biochar may better improve soils that are degraded and otherwise unproductive.

    Project objectives:

    The aim of this project was to investigate how biochar affects plant growth and yield, as well as soil nutrients and health, in the first two years of production. The first objective was to look at what affect, positive or negative, biochar would have on plant fitness and fruit yield. Plant fitness included plant growth, chlorophyll, and fruit yield. The second objective aimed to record the effect biochar had on soil quality including nutrient retention.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.