Rapid High Health See Potato Production Using Aeroponics (Part 2)

At Massey University we have compared the traditional system of high health seed potato tuber production with a number of different hydroponic systems.

In two distinct studies we compared the productivity of a number of potato cultivars in four systems, namely:

1. Standard treatment in a bark medium

2. Deep Flow hydroponic system

3. Nutrient Film Hydroponic system

4. Aeroponics.

In all cases the aeroponic system produced a larger number of tubers, even though in one experiment the actual yield (weight) of tubers was higher in the bark treatment.

(Table I and Table II)

System No.Tubers/plant Mean tuber weight(g) Yield/plant (g)

Bark 15.40 12.15 190.1

DeepFlow 29.60 2.07 57.9

NFT 15.31 3.66 57.0

Aeroponics 37.34 2.45 82.6

Table I. Effect of different production systems on the yield characteristics of potatoes. (Study1)

System Notubers/plant Mean tuber weight (g) Yield/plant (g)

Bark 5.34 35.8 191.1

Deep Flow 7.97 9.3 73.9

NFT 6.37 10.0 63.4

Aeroponic 19.34 10.8 208.2

Table II. Effect of production system on tuber number and yield (study 2).

In the second study the aeroponics system gave a similar yield to the conventional bark system, but resulted in a marked increase in the number of tubers. As the objective of the exercise is to increase plant numbers clearly this achieved this objective. Furthermore using aeroponics it is possible to achieve synchronous tuber initiation, so that the bulk of the tubers are all of the same size. It is difficult (if not impossible) to achieve this in a bark based medium.

We do not understand why, but we have found that stressing the plant for a short time is adequate to cause tubers to be initiated, and that this has considerable merit, because it enables us to obtain near synchronous tuber initiation, and thus ensure that (in theory at least) all the tubers can be harvested at the same time.

We have stressed the plants by exposing the roots to a low pH for 24-48 hours, but equally some other form of stress (e.g. moisture stress) might be just as effective. Because of the concern for incorporating biochemically active chemicals into the plant material we have intentionally avoided using any growth regulators.

By obtaining synchronous tuber initiation mini-tuber harvesting can be carried out over a restricted period of time.

We found no major differences in the behaviour of the different cultivars, although some produced a considerably greater number of min-tubers per plant. There was one single clear cut difference between cultivars, however, and this was in relation to dormancy.

Mini-tubers from this system can not be immediately planted in the field, as they need to undergo a maturing process to overcome any dormancy.

We have demonstrated that it is possible to reduce dormancy by using gibberelic acid – although there are major cultivar differences, but in the final analysis it would appear that refrigerated storage is probably the safest and least environmentally sensitive technique to overcome dormancy.

Conclusions:

1. Aeroponics appears to offer similar or better yield to the production in solid media.

2. Production in NFT and DeepFlow is inferior to aeroponics.

3. Although aeroponics and solid media may produce similar yields per plant, the aeroponics system produced a more even sized tuber (and many more of them).

4. When the objective is to bulk up the high health plant material rapidly then aeroponics offers a very suitable system.

5. Aeroponics offers the opportunity to mass produce high health mini-tubers, which can be easily transported world-wide by airfreight, and can be easily cool stored because of very low mass.

6. This offers all countries the opportunity to use high health mini-tubers for rapid production of a seed potato crop.

Addendum:

In a recent visit to Uganda I (MAN) found that yields of potatoes grown from newly imported high health plant material (as tubers) could approach 25 t/ha, but over a period of 5 years yield declined to some 5t/ha due to the proliferation of systemic diseases. This effect was in this case exacerbated by the philosophy of selling the big tubers, consuming the medium sized tubers at home, and using the small (and most likely diseased tubers) as seed for future crops, but it was also not helped by the lack of continuity of supply of high health seed tubers.

Even worse is the fact that with low potential yields blight control and fertilizer application is likely to be uneconomic, and labour requirements for a poor crop are very similar to those for a heavy yielding crop, in fact may be even higher, because a poor crop usually requires more weed control.