Articles
THE USE OF SPAD-502 CHLOROPHYLL METER FOR DYNAMICALLY OPTIMISING THE NITROGEN SUPPLY IN POTATO CROP: FIRST RESULTS
Article number
627_29
Pages
225 – 230
Language
English
Abstract
An experiment was carried
out in 2000 on potato cv.
Primura to test the usefulness of SPAD threshold
values in decision making for supplemental nitrogen supply.
A non-fertilized
control was compared with nine fertilized treatments receiving 30 kg ha-1
of N (urea 46% N) at crop emergence plus supplementary nitrogen which was
applied as follows: i) five treatments provided increasing ratesof N (30, 90, 150, 210 or 270 kg N ha-1,
urea 46% N) distributed 18 days after emergence, (conventional fertilization,
CF); ii) four treatments provided supplemental nitrogen application (urea, 46%
N) whenever the SPAD values fell below the critical value of 39 SPAD (dynamic
fertilization, DF). This critical level corresponds to 10% deviation from
threshold value of 44-45 SPAD calculated in a previous work.
Each time,
increasing rates of N were distributed to the soil (30, 60 or 90 kg N ha-1
– 30 DF, 60 DF and 90 DF), or 9.2 kg N
ha-1 was applied via foliar spray (foliar DF). The number of N
applications was 4, 3, 3 and 5, and the
total amount of N applied to the crop was 120, 150, 210 and 76 kg N ha-1,
for the 30 DF, 60 DF, 90 DF and foliar DF treatments, respectively.
Yield
response to CF treatments showed best result with 120 and 180 kg N ha-1
(120 CF = 30+90 kg N ha-1; 180 CF = 30+150 kg N ha-1).
Yield of DF treatments did not differ significantly from 120 CF and 180 CF.
This yield was achieved with a noticeable reduction in total N application for
foliar DF treatment (reduction of 37% and 58% as compared to 120 CF and 180 CF,
respectively)
out in 2000 on potato cv.
Primura to test the usefulness of SPAD threshold
values in decision making for supplemental nitrogen supply.
A non-fertilized
control was compared with nine fertilized treatments receiving 30 kg ha-1
of N (urea 46% N) at crop emergence plus supplementary nitrogen which was
applied as follows: i) five treatments provided increasing ratesof N (30, 90, 150, 210 or 270 kg N ha-1,
urea 46% N) distributed 18 days after emergence, (conventional fertilization,
CF); ii) four treatments provided supplemental nitrogen application (urea, 46%
N) whenever the SPAD values fell below the critical value of 39 SPAD (dynamic
fertilization, DF). This critical level corresponds to 10% deviation from
threshold value of 44-45 SPAD calculated in a previous work.
Each time,
increasing rates of N were distributed to the soil (30, 60 or 90 kg N ha-1
– 30 DF, 60 DF and 90 DF), or 9.2 kg N
ha-1 was applied via foliar spray (foliar DF). The number of N
applications was 4, 3, 3 and 5, and the
total amount of N applied to the crop was 120, 150, 210 and 76 kg N ha-1,
for the 30 DF, 60 DF, 90 DF and foliar DF treatments, respectively.
Yield
response to CF treatments showed best result with 120 and 180 kg N ha-1
(120 CF = 30+90 kg N ha-1; 180 CF = 30+150 kg N ha-1).
Yield of DF treatments did not differ significantly from 120 CF and 180 CF.
This yield was achieved with a noticeable reduction in total N application for
foliar DF treatment (reduction of 37% and 58% as compared to 120 CF and 180 CF,
respectively)
Authors
G. Gianquinto, P. Sambo, F. Pimpini
Keywords
Foliar fertilization, N fertilization, Solanum tuberosum, SPAD Threshold Value, supplementary fertilization, tuber production
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