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Roots below one meters depth are important for nitrate uptake by annual crops

Kristensen, Hanne L. and Thorup-Kristensen, Kristian (2006) Roots below one meters depth are important for nitrate uptake by annual crops. [Rødder under 1 meters dybde er vigtige for et-årige afgrøders optagelse af nitrat.] Speech at: The American Society of Agronomy - Crop Science Society of America - Soil Science Society of America International Annual Meetings, Indianapolis, USA, November 12-16, 2006.

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The root depths of annual crops vary from 0.2 m to more than 2 m depending on root growth rate and length of growing season. However, studies of root growth and N uptake are often restricted to a depth of 1 m or less, as root biomass is assumed to be negligible below this depth. We have studied the importance of root growth and N uptake to a depth of 2.5 m in fully grown field vegetables and cover crops by use of minirhizotrons and deep point placement of 15N. Deep rooted crucifereous crops were found to have high root densities to a depth of 1.5-2 m and high 15N uptake to this depth. Uptake was significant near the bottom of the root zone at a depth of 2-2.5 m where root density was low. Here N uptake rates were higher per unit root length compared to more shallow depths. Thus, deep roots were more important to crop N uptake than indicated by their density. In studies where subsoil nitrate was high, deep rooted crops could reduce soil nitrate content by up to 100 kg N ha-1 at a depth of 1-2.5 m over the growth season compared to shallow rooted crops. The effects on crop N uptake, when matching deep rooted crops with high subsoil nitrate in crop rotations, will be illustrated by modelling. The work shows that knowledge of the interactions between root growth and soil N below a depth of 1 m are important to understand crop N uptake and nitrate leaching from agro-ecosystems.

EPrint Type:Conference paper, poster, etc.
Type of presentation:Speech
Subjects: Soil > Nutrient turnover
Crop husbandry > Crop combinations and interactions
Crop husbandry > Production systems > Vegetables
Research affiliation: Denmark > DARCOF III (2005-2010) > VEGQURE - Organic cropping Systems for Vegetable production
Denmark > AU - Aarhus University > AU, DJF - Faculty of Agricultural Sciences
Deposited By: Kristensen, Ph.D. Hanne Lakkenborg
ID Code:11462
Deposited On:28 Nov 2007
Last Modified:12 Apr 2010 07:35
Document Language:English
Refereed:Not peer-reviewed

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