Funded by: MTI Cluster Enhancement Award from Maine Technology Institute, Maine Potato Board and Maine Seed Potato Board
Project
Duration: April 1, 2006 to Dec 31, 2006
Principal
Investigator:
Dr. Vikram Bisht, Porter Seed
Potato Farm
12 January 2007
EXECUTIVE SUMMARY
A small scale trial was conducted in the summer of 2005
to determine the potential of minituber production using nutrient film
technique (NFT) and compare productivity against the existing production system
using soil-less growing mix. The trial
on the production of minitubers using the NFT system was repeated in 2006. In 2006, well water was used for the trial
in the initial stages, but later changed to reverse osmosis water. The planting
for the trial was started in the last week of June and the final harvesting was
done by October 31. Six varieties were
planted in NFT system, but many more varieties were planted in grow-mix
beds. Plants were spaced at 4” in the
NFT and in the grow-mix beds.
Minitubers upto 7mm size were harvested, data on number and total weight
were collected. Analysis of the data showed
that NFT system produced 4 to 8 times more tuber mass and 9 to 24 times more
tuber numbers than the regular greenhouse productivity. It could be inferred from this preliminary
trial that NFT system has huge potential to help the Maine seed potato industry. Delay in planting of trial and high
temperature during early growth stage of the seedlings may have prevented the
NFT system from reaching its full potential of production.
The trial of 2005 trial
was repeated in 2006 summer.
Minituber production in
North America is being done using either the grow-mix beds or the hydroponics
systems. The primary hydroponics system being used is the NFT system, as
understood from discussions with various potato industry people. However, it is
difficult to obtain reliable data on the details of NFT or other production
systems.
Many
states in the USA and provinces in Canada have fewer (five to six) field
generations of potatoes compared to the seven allowed in Maine. Reduction in the number of field generations
would normally improve potato tuber quality in the later generations by
reducing exposure to soil-borne diseases and viruses, but it would necessitate
a much higher production of early generation seed. This would require increased production of minitubers. Also, to
stay competitive and be able to quickly adopt new varieties, a higher
productivity system would be extremely helpful to the Maine potato
industry. Some research has been
conducted on such potato production systems in greenhouses, but only a limited
amount has been published or made public. It is therefore important to
understand the impact of various input factors, which may influence the
productivity of the system at our own facility.
To
stay competitive, Maine potato industry needs to employ innovative means to
increase its high quality seed production capability. As done by other
agencies, it is essential to keep the details of this technology confidential.
EXPLANATION OF THE PROJECT:
The trial was conducted
with the following objectives:
The research trial involved growing potato minitubers in the NFT system and comparing the production to the presently used system of plants in grow-mix beds.
1.
Systems to compare
Greenhouse Set up: To reduce the cost of water de-ionization, deep well
water, with an EC of 0.02 was used. The
greenhouse poly-film cover, which was removed after the 2005 trial, had to be
put back on. To prevent high
temperature in the greenhouse (as in 2005), shade cloth was also put on. The
sides (4 ft. high from the ground up) and the end walls were covered with
screen to allow natural air-flow and still keep it aphid-proof. The internal floor space of the greenhouse
was 30 ft x 48 ft, and was 12 ft. high at the central area.
Planting: In May, a large number of
seedlings were started for the varieties to be used in the trial so that there
would be no shortage of uniform and good-sized plantlets. In early to mid June, the potato
plants were being readied for later planting in the greenhouse. Two NFT systems
B1 and B2, with independent re-circulation systems, were set up in mid-June.
System B1 had one re-circulation system feeding nutrient solution into 6
separate grow-trays (approx. 2.5 ft x 4 ft); while in system B2 there were no
separate trays, but a single large B&W poly-lined bed (approx. 4 ft x 12
ft). The system was tested for a couple
of days to ensure proper running. First planting in the B1 system NFT trays was
done on June 19, finishing B1 system planting on June 27. NFT system B2 was planted on July 6 and 7;
two white tuber varieties were separated by red tuber variety, Norland (Table 1
& 2). In total 6 varieties were planted in the 2 systems. A third NFT system, B3, was set up and
planted from late July into early August. This system consisted of ten 10 ft.
long trays fed with nutrient solution from a 3rd nutrient
re-circulation system. Nine different varieties were planted in this system,
using older seedlings (left over from B1 & B2 systems and grow-mix bed
plantings).
In
regular grow-mix beds seedlings were planted at 400 plants/bed or lower, having
a plant to plant spacing of about 4”.
Fertilizer application was as per standard protocol used at the farm.
The NFT system
required daily monitoring and adjustment of the nutrient status, while the
grow-mix beds needed daily watering and timely fertilizer application. Plants in both systems were sprayed with
Champion WP fungicide to protect against late blight infection. Time for various activities in the trial was
recorded as best as possible.
Harvesting: In the NFT system, minitubers were harvested upto 7
times from the same plants, depending upon the NFT system and the variety. As far as possible, minitubers 15mm or
larger were harvested. Harvesting dates for the NFT tubers ranged between Aug
28, and the final harvesting on Oct 31. The grow-mix bed plants were harvested
only once, on Oct 12 &13. The comparisons between grow-mix beds and NFT
system are made based on average of 20 grow-mix beds and 33 NFT var-system
trays. NFT system B3 had poor plant growth, and so data were not utilized for
comparisons; but have been presented.
Data were analyzed non-statistically, due to lack of space for
replications
Results of the Trial:
The
nutrient circulation system set-up worked reasonably well. Temperature records of the screenhouse and
the nutrient solution in system B1 showed that the air temperatures reached a
peak of 39 oC (102.2oF) on one day; also the nutrient
solution temperatures sometimes went above 20 oC (68oF)
(which is considered to be above the optimal temperature). Below are the
monthly high and low for the air and nutrient temperatures:
|
|
Air
Temp Low
(Morning) |
Nutrient
Temp Low (Morning) |
Air
Temp High (Afternoon) |
Nutrient
Temp High (Afternoon) |
|
June |
16 |
14 |
38 |
24.5 |
|
July |
19.3 |
16.2 |
39 |
26.6 |
|
Aug |
9.8 |
10.7 |
31 |
19.3 |
|
Sep |
0.8 |
4.6 |
28.7 |
20.8 |
|
Oct |
-2.0 |
3.1 |
28.2 |
19.6 |
A liquid cooling
system was used in the NFT systems to buffer the nutrient solution temperature.
However, the cooling system’s capacity was seriously challenged at very high
and very low temperatures. Below 10C
and over 20C, the nutrient solution temperature affects plant growth and tuber
production.
Screenhouse set-up worked well for the NFT trial
(photos).
Early in the
trial, the plants showed signs of nutrient imbalance, and could have been due
to the well water being used. The
nutrient solution had to be dumped a few times, and de-ionized water was used
to make the nutrient solution. The plants recovered from the signs of nutrient
imbalance. Reverse osmosis water was
later used to make up for the regular water losses due to plant uptake and
transpiration.
As in 2005, in
2006 also, system B2 produced much more than B1, even though B2 planted later-
the average weight of MTs potentially produced by 400 plants in B2 (142 lbs)
was about 80% times higher than from B1 (79 lbs), and number of MTs was 20%
higher. Within each NFT system, there
was significant variation between varieties, the number of MTs produced per
plant ranged from low of nearly 11.6 to about 39.1 (Table 1). Production in B3 system was extremely poor
and may be due to algae growth in the system and use of older seedlings. The
plants grew very poorly and only one or two harvestings were possible.
Average
production of 8.56 lbs per grow-mix bed with 400 plants is close to what has
been normally been observed in our greenhouses. This production would have been
higher, but for the poor performance of Norwis, RB and Green Mountain
varieties. No specific reason could be ascribed to their poor production.
Productivity
per plant of minitubers in the NFT systems (Bench 1 and Bench 2) was
significantly higher than the grow-mix beds (Tables 1, 2 & 3). Number of
MTs in the NFT system were 14.2 times more than the grow-mix beds, while the
mass of MTs produced was 12 times higher.
The overall picture of the two systems shows that NFT produced 26.
MTs/plant compared to 1.81 in the grow-mix beds.
|
|
|
Total Plants Used |
Total MTs |
MTs/plant |
|
|
2005 |
NFT (Both Benches) |
409 |
10,291 |
25.16 |
15.9 |
|
|
Grow-Mix Beds |
7817 |
12,323 |
1.58 |
1 |
|
2006 |
NFT (2 systems) |
306 |
8869 |
26 |
14.2 |
|
|
Grow-Mix beds |
10485 |
19001 |
1.81 |
1 |
Another
way to compare the data was comparison of production by 400 plants in the two
systems in 2006:
|
Production System |
Minitubers from 400 plants |
|
|
Number |
Weight (Lbs) |
|
|
NFT |
10393 |
100.1 |
|
GrowMix Beds |
759 |
8.56 |
|
NFT : GrowMix Beds |
13.7 : 1 |
11.7 : 1 |
In 2006 trial,
there was increased automation for nutrient management, however, continuous
monitoring was essential for recording data. Due to experience gained in the
first year and also due to increase in automation, less time was spent on the 2
older re-circulation systems; however, the 3rd system of ten 10 ft.
long trays took more time than expected. Also this system did not perform upto
expectation. This may partly due to algae growth and older seedlings. This
system would be improved to prevent algae growth and younger seedlings will be
used.
All funds for the
research grant were received in a very timely manner
|
|
Granting Agency |
Award |
|
Aug 01 |
Maine Technology Institute |
$ 7,250 |
|
Sep 27 |
Maine Potato Board |
$ 5,000 |
|
Allocated, in-kind |
Maine Seed Potato Board |
$ 5,500 |
|
|
|
$17,750.00 |
Screenhouse
set-up worked well for the NFT trial (photos included).
Conclusions:
In
the NFT system, a significantly higher number and also higher mass of
minitubers were produced. Minitubers from NFT system were harvested when they
reached the desired size; uniform size of minitubers is helpful during planting
and leads to uniform emergence.
Production
in system B3 was poor due to late planting and growth of algae in the system;
this will be rectified in 2007 production.
Deep well water at the farm, in-spite of having very low EC, is not good
enough for NFT production system. Reverse Osmosis water will be used for future
production; and this may be a cheaper option than de-ionized water.
The
fact that the number of minitubers produced per plant in NFT was significantly
higher than in grow-mix beds, there is a good potential for using this
technology at the Porter Seed Potato Farm. Adopting this technology at the Farm
would be cost effective due to fewer plantlets needed for production and also
savings on time and labor costs for tissue culture too. Another critical benefit of using this
system would be rapid increase of early generation seed, when the industry
needs the change; e.g. change in preference of clones of Russet Burbank, Red La
Soda and Snowden.
To exploit the full potential of the NFT system for
minituber production it would be important to set a full-scale commercial
system. Help from Maine’s potato industry would be needed to achieve the goal.