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Proceedings Crop Production In Northern Britain 2018
INFLUENCE OF FOLIAR STABILISED NITROGEN ON POTATO TUBER YIELD
D J Marks, S Wilkinson and A K Weston
Levity Crop Science, Myerscough College, Preston, Lancashire, UK
Summary: This study demonstrates that form and stability of foliar applied
nitrogen has an influence on yield. Foliar applications of stabilised NH2 gave
significant yield increases of 4.7% on potato cv. Sassy, whilst conventional foliar
nitrogen treatments had no significant effect on marketable yield. The positive
effects of the foliar NH2 treatment used in this study reflect similar yield
improvements to those that have been reported in efficacy trials in France, Ireland
and the Netherlands (Headland Agrochemicals Ltd., personal communication).
The form of nitrogen taken up by plants has an influence not only on total growth, but also on
resource partitioning. This has been suggested to be linked to the findings that exposure to
different forms of nitrogen (nitrate, amine and ammonium) has differing effects on the rate of
production, transport and relative abundance of the growth hormones cytokinin and auxin
(Kiba et al., 2011). Nitrate promotes or stimulates leafy growth and apical dominance rather
than lateral root production (Chamizo-Ampudia, 2017).
Nevertheless, little work has been done previously to establish the effect of form of N on crop
production. From a practical perspective, conventional nitrogen fertiliser is not environmentally
stable, with typical losses through processes such as surface runoff, leaching and formation of
volatiles being greater than 65% of that applied (Raun and Johnson, 1999). Furthermore,
nitrogen is largely taken up as nitrate regardless of the form in which it is supplied.
When growing potatoes commercially, nitrogen uptake and use efficiency is dependent on
how, when and where it is applied. For example, late applications of foliar N can be
counterproductive as they have a tendency to produce leaves rather than tubers. Potato
varieties vary considerably in their ability to take up applied nitrogen and convert it into growth
(nutrient use efficiency), and all varieties fail to take up significant amounts of the nitrogen that
is applied to them (Zebarth et al., 2003). Previous research has given rise to the much
improved efficiency with which potato crops use nitrogen in the 21st century, however N form
is still a relatively overlooked avenue of exploration.
It has been demonstrated in other crops that exposure to small bursts of NH2 can have an
effect on plant architecture disproportionate to the quantity applied (Bergmann and Eckert
1990). This study looks at field results from Yorkshire (UK) using foliar applications of Lono (a
stabilized NH2 formulation from Levity Crop Science) and the effects on yield of potato. The
study compares this with the effects of two non-stabilised foliar nitrogen formulations. Also
discussed are data from studies in France, Ireland and the Netherlands using foliar
applications of the stabilised NH2 formulation on different varieties.
MATERIALS AND METHODS
Yorkshire Efficacy Trial
This trial was carried out in 2016 in the North of England at Stamford Bridge, East Yorkshire,
UK. The study was a randomised block design with 4-10 replicates of each of four treatments,
using the indeterminate potato variety Sassy. Standard soil fertilisation at the site was 200
kg/ha nitrogen. The control treatment contained no additional foliar nitrogen (treatment 1, 4
replicates). Treatments 2-4 consisted of supplemental N applied to the developing crop as
liquid foliar nitrogen treatments. The second and third treatments used two standard,
commercially available liquid foliar nitrogen treatments (standard A and standard B, 4
replicates), and treatment 4 consisted of a liquid foliar stabilised NH2 treatment (10 replicates):
Standard A (treatment 2) contained 340 g/l N (37 g/l NO3, 140 g/l NH4 and 163 g/l NH2),
applied in 3 litres/ha.
Standard B (treatment 3) contained 330 g/l N (49 g/l NO3, 67 g/l NH4 and 214 g/l NH2), applied
in 3.3 litres/ha.
Stabilised N (treatment 4) contained 195 g/l N (65 g/l NO3 and 130 g/l stabilised NH2), applied
in 5 litres/ha
Knapsack-applications of foliar N treatments were supplied to the 22 plots as detailed in
Tables 1 and 2.
Table 1. Foliar Nitrogen Application Rates
(1.02 kg N)
(1.02 kg N)
(1.02 kg N)
(1.02 kg N)
(1.09 kg N)
(1.09 kg N)
(1.09 kg N)
(1.09 kg N)
(0.98 kg N)
(0.98 kg N)
(0.98 kg N)
Table 2. Plant Growth Stage* Schedule and Soil Moisture and Compaction Status
for the Four Foliar Nitrogen Application Occasions
*according to BBCH (Biologische Bundesanstalt, Bundessortenamt und Chemische
The crop was harvested on the 31st of October 2016, and all tubers (inclusive of green or
cracked) from each plot were weighed (to achieve a total yield per plot – see Table 3) and
graded for size. After discarding the damaged tubers and those under 45mm diameter, the
weight of the marketable yield was measured. Each treatment was compared to the others
using a simple t-test, and this showed that only treatment 4 (stabilised N) had a marketable
yield that was significantly larger than that of the control (p=0.1. When unmarketable tubers
were also included in the analysis, treatment 4 still had a significantly greater total yield than
controls (p=0.1, and, additionally, so did, treatment 3 (standard B).
Foliar application of stabilised NH2 as used in this study, but not that of the two standard foliar
N fertilisers, had a significant effect on marketable yield, with a 1.713 T/ha (4.7%) yield
increase compared to the control.
Table 3. Yield data at harvest (31.10.16). *Significance levels (p<0.1) are denoted
as xa-b, and differing letters pertain to significant differences between
treatments (within columns).
Total Yield (%
(% of control)
This study shows that form and stability of applied foliar nitrogen influences its efficacy as a
nutritional fertiliser for the production of potato tubers. Three formulations were used, which
supply similar levels of nitrogen to the plants (in fact the stabilised NH2 supplied at least 110
g/ha less N to the crop, furthermore this was only applied on 3 rather than 4 occasions). On
this occasiontwo conventional formulations had no significant effect on marketable yield. By
contrast, the stabilised NH2 formulation significantly increased marketable yield in this field
study by 1.713 T/ha (4.7%).
It has not previously been demonstrated that stabilised NH2 can increase the tuber yield of
crop plants, although grain formation and basal internode growth in pot-grown rye and barley
plants has been shown to increase when monoethanolamine was applied to the foliage of the
plants (Bergmann and Eckert 1990, Bergmann et al. 1991).
Given that the three kilos of nitrogen applied in the study is less than the nitrogen content of
the 1.7 ton extra yield achieved per hectare using the stabilized NH2 treatment it can be
concluded that the growth is not due to higher access to nitrogen alone. A possible
explanation for this is that exposure to foliar stabilised NH2 has an effect on growth partitioning
of potato crops, with the treated plants disproportionately increasing tuber growth and
development. It has long been known that N nutrition affects plant growth hormone levels and
transport in potato (Sattelmacher and Marschner 1978). One hypothesis is that stabilised N
affects plant hormone synthesis and/or transport in a manner that is preferential for tuber
formation as opposed to vegetative top growth (Ewing 1995). In contrast, Bergmann and
Eckert (1990) found that nitrogen levels were preferentially increased in the basal internodes
of cereal tillers under monoethanolamine nutrition, and proposed that this was the reason for
the increased growth in this region.
The trial data described here that came from a farm in Northern Britain is consistent with data
from other similar trials where tuber yield increases were also seen in France, the Netherlands
and Ireland. This data is summarised in Table 4 (from Headland AgroChemicals Ltd., personal
communication). Thus we can conclude that stabilised NH2 may be a novel method for
increasing potato harvests from our fields through improvements in crop nitrogen use
Table 4. Supplementary data summary of European field trial results using
the stabilised NH2 formulation in addition to standard farm fertiliser
Number of 5
*p=0.1 (where the yield increase was calculated via analysis of variance and Fishers
LSD to be significantly higher than that in the control plots treated under farmer
standard conditions [level of N dependent on variety requirement and season length]).
Levity Crop Science Ltd supplied Lono, the stabilised NH2 formulation used in the study. The
crop trial was carried out by Nigel Metcalfe on behalf of NDSM Ltd.
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