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Nitrogen Sources for Bean Seed Production

Westermann, D.T. and Kleinkopf, G.E. and Porter, L.K. and Leggett, G.E. (1981) Nitrogen Sources for Bean Seed Production. Agronomy Journal. 73:660-664.

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Beans (Phaseolus valgaris L.) often respond to N fertilization;
however, N fertilization is not practiced for
maximum seed production in southern Idaho. This suggests
that the symbiotic relationship and/or soil N sources
can provide most of the N needed by this legume. Our
objective was to evaluate the relative contribution of the
symbiotic-nonsymbiotic N sources by studying the effects
of N fertilization on the symbiotic N₂ fixation and seed
yields under field conditions. Experiments were conducted
on silt loam soils belonging to the Portneuf series
(Xerollic Calciortnids). An acetylene reduction (AR)
method was used to determine the effect of N fertilization
treatments on the relative seasonal Ng (AR) fixation.
The symbiotic N₂ fixation was also estimated by the
equation, N₂ = Nup — (Nl + Nm - Nh) — ⍺Nf, where Nup
is the accumulated N uptake measured near physiological
maturity, Nl and Nh are the amounts of soil NO₃-N in
the root zone before planting and near physiological
maturity, Nm is the N mineralized from soil organic N
sources, and ⍺ is the recovery of the N fertilizer (Nf)
applied. Estimates of the N fertilizer recoveries were obtained
from two experiments using 15N-depleted (NH₄)₂SO₄.

The symbiotic N₂ relationship contributed up to 90
kg N/ha, which was 40 to 50% of the total N found in
bean plants near physiological maturity. The amount of
symbiotic N₂ fixed decreased as the available soil N or
fertilizer N increased, and increased as the N required
by the individual cultivars increased. The response to N
fertilization depended upon the cultivar, as well as on
the N available from soil sources. Measured fertilizer N
recoveries ranged from 7 to 33%. An average of 52% of
the total N uptake near physiological maturity was taken
up after the maximum symbiotic Ng(AR) rate occurred;
while the seed contained an average of 60% of the total
N uptake. A low N fertilization rate (< 50 kg N/ha)
when the soil Nl was low (<50 kg N/ha) ensured an
early vigorous plant growth but did not always increase
seed yields. Higher N fertilization rates may be required
on soils with lower amounts of mineralizable N.

Item Type: Article
NWISRL Publication Number: 0463
Subjects: Irrigated crops > Bean / dry bean
Mass Import - autoclassified (may be erroneous)
Depositing User: Dan Stieneke
Date Deposited: 20 Nov 2010 21:52
Last Modified: 23 Jan 2017 18:50
Item ID: 376