NOTES ON POTATO GROWING AND HANDLING.

New Zealand Journal of Agriculture, Volume XVIII, Issue 3, 20 March 1919, Page 157

NOTES ON POTATO GROWING AND HANDLING.

By

J. BEVERLEY,

Assistant Agriculturist

HARVESTING AND STORAGE

This being the season for harvesting and storing the potato crop, it may be well to deal firstly with that phrt of the subject. Degeneration in seed-potatoes is brought about more ' quickly by improper storage than from any other cause.

The death of the haulm is the signal for digging the main crop. For the early market potato-growers do not .wait for this, but are governed by the market price and the size of the tubers. As long as any portion of ■_ the haulm is green the tubers can continue to grow, and the longer the haulm is kept green and free from blight the better the crop will be. Experiments have shown that more than one-third of the merchantable crop is made during the last month of growth. In harvesting the crop it pays to handle the tubers 'carefully, as any inj ry~ affects their keeping-qualities. * It is a mistake to allow potatoes to stand in sacks for any length of time in the open field after lifting, as the edible tubers get green and unnaturally heated if the weather is hot, and when carting them to the store they get bruised. ’ Far better is it when lifting the crop for the pickers to have baskets and empty the contents into a cart moving along with them. With a stand-cart and a go-cart the work proceeds without any loss of time.

When the load of potatoes arrives at the clamp or pit or potatocellar it should be backed into position and tipped. The clamp or pit should never be more than 5 ft. wide at the base —perhaps the best width for the base of a potato-clamp is 4 ft. 6 in., with a height of 3 ft. 6 in. After the potatoes are tipped they should be placed into position with a sippet/ This tool shovels up the tubers without damage when lying on the ground ; the sides of a clamp are also formed with the sippet. As soon as the clamp is a few yards long a start should be made to cover the sides with straw. The straw should be long, strong,, and clean, and placed on the sides to a thickness of at least 4 in. After the two sides are covered straw should be placed on the apex, or top, and bent over. It ■ is best not to cover the sides all over with soil immediately, but to leave spaces here and there for the heat to escape. In a few days the sides may be covered with soil, leaving about 12 in. of straw at the top uncovered. It is not necessary to cover the top with soil unless very severe frosts are experienced during the winter.

Never put potatoes in clamps or pits on the same place in succeeding years. • In this way sources of . disease-infection may be avoided to a certain extent. Avoid covering potatoes with wet straw, and do not forget that the tubers should be ripe if they' are to be pitted. When a potato is ripe and lifted in fine weather, clamped upon dry and welldrained soil, not in too considerable a bulk, well covered with straw, and ventilation provided, there ought to be no cause for loss to any extent. / ■ ' • . ■

Darkness , and cool temperature are primary, requisites' in the successful storing of potatoes' through the winter. In harvesting, as well as in storage, the tubers should be exposed to the light as little as possible. When potatoes are allowed to green they become useless for culinary purposes, and, some authorities say, poisonous. Warmth encourages sprouting, which reduces the value of potatoes both for planting and eating. For storage the temperature should be an even one of 35 0 F. and not more than 40° F. ' The freezing-point of potatoes is 30° F. In countries where low temperatures are experienced during winter, pitting potatoes above ground in the manner described is the cheapest and most satisfactory. It is not claimed, however, that this method is suitable for the warmer parts of New Zealand. ■

If the water-level does not rise too. near the surface during winter an inexpensive potato-cellar may be made by merely excavating a trench 5 ft. or 6 ft. deep and 8 ft. wide, and as long as is needed. When the crop is harvested the cart or dray is tipped on the side of the cellar. Never pile potatoes more than 5 ft. deep. Always make a cellar in a line with the prevailing air-currents. The roof should be given a pitch just sufficient to shoot water and afford sufficient strength. A small gutter or . ditch should be dug along either side to carry away water shed by the roof. Up-to-date cellars or underground pits are constructed so that air may pass through at night, and, if the weather is hot, be closed up during the day. I have heard of an instance where potatoes were stored in an old mine-tunnel and remained good for two years., A current of air passed through the tunnel and the temperature remained about 40° F. .

1 The method of storing seed-potatoes at Moumahaki Experimental Farm is to place them on wire-netting benches under pine-trees as soon as they are lifted. (See Journal for July, 1916.) When potatoes are exposed in this manner all winterit is necessary to see from time to time whether the larva of the potato-moth is doing any damage. If so, it may be necessary to dip or spray the tubers with arsenate of lead, using 1 lb. to 50 gallons of water.

For storing small quantities of potatoes kerosene-tins can be used — three sides being cut at the top to form a lid. A tin holds about 28 lb. when full. Dig a trench about 3 ft. deep and 15 in. wide, so that a tin will lie lengthwise. Place the lid close up to the bank-side, so that the lid may be . kept closed, and this will prevent rats doing damage. Cover the top with a sheet of galvanized-iron sheeting. This is a very convenient method of storing a few special potatoes, or where there are several varieties which have to be kept separate for seed purposes.

SELECTION AND HANDLING OF SEED.

Whenjthe potatoes are ripe enough to keep, but before they are dug, and when the haulm is still green and in good condition, is the time to select potatoes to be saved for seed. Go into the potato-field and look for strong, healthy tops, and see if the soil is being well raised up by the growing tubers. If a stake is placed at each root selected, the lifting can be done later or as soon ’ as sufficient selected roots have been secured. There is no better way of selecting potatoes than by taking seed from perfect roots. Seed should be selected only from

roots producing .first-class marketable potatoes, in the. growing of which there is little waste of plant-food. 'The true breed characteristics • of a variety can be maintained by selection.

■ When selecting potatoes it is ' as well to • know something about the quantity required to plant an acre. If the rows are. 28 in. apart there will be 28 rows in 22 yards, and 280 chains of rows in one acre — that is, 6,160 yards to plant. Spaced at 18 in. apart, it will require 12,320 tubers to plant 1 acre if the tubers weigh 2 oz. each, 14 cwt. of seed is required. The same weight of seed is required if large tubers • (4 oz.) are cut’ in half. x

. In my opinion it is better to plant cut tubers at once and to place the cut surface uppermost when planting. The set is not so likely to decay before rooting, and if there are sprouts they are not knocked off in the covering. According to tests recorded in the Journal of the Royal Horticultural Society, covering the cut surface with plaster-of-paris - gave the best results as to weight of crop, sulphur being also good. Lime was found to be injurious. It was also found that the sets that were cut immediately before planting gave a better return than those which were cut some time previously. Where'the seed of the variety is limited a larger yield will be obtained if the sets are cut, but the average return per plant will not be so large.

Quoting the same authority, as regards the size of seed it was found rnat tubers weighing between 2 oz. and 3 oz. were the most economical and reliable. It was also found that the greater the space given to the individual plant the greater the yield of that plant would be, but the greater number of plants on a given area the greater the total yield of that area would be. In my own experiments I have found that the greatest yield per acre is obtained when the sets are planted 12 in. apart. As the distance increases between the sets the total yield decreases. " •

If early crops are required it is good practice to sprout the tubers, being careful to get short sturdy sprouts, which are not knocked off by planting. Another advantage to be gained by sprouting potatoes is that all the tubers affected with spindle-sprout disease may be picked out, as when these are planted blanks will be found. Light and air are necessary to get short sturdy sprouts. . When there is no fear of spindle-sprout disease it is better to put unsprouted potatoes in for the main crop. Potatoes will not sprout if stored at a low temperature.

The practice of greening seed-potatoes is resorted to as a rule when crops intended for seed purposes are lifted when the skins slip — is, before they, are ripe, and the skin is not set. If tubers are greened they should be on the ground, and not be turned to green on both sides. There is no harm done in greening seed-potatoes if the potato-moth is not about; that point must be considered. For my part, I think that the practice of greening sometimes receives the credit which is more properly due to the immature condition in which the sets for planting were saved in the previous summer or autumn. The maturity of the seed seems to have an important bearing on productiveness. Potatoes not quite mature frequently give the larger yield. The potatoes in Scotland practically never fully mature, being often cut down by frost in the autumn ; yet Scotland is at the present time the

potato seed-bed of the world. From every European State, from North and South America, Africa, and Australasia, growers are sending for Scotch seed. Much in the same way in New Zealand do we send to the South Island when we require a change of seed in the North Island.

In my experience the benefit of a change of seed is marked. It should come from a colder climate and a distance away—not necessarily from the South Island—as seed from a high altitude or a late district makes a good change for the drier and earlier districts. When one has a good line in potatoes it should not be allowed to deteriorate. Select seed every year, and lift it for seed whilst the haulm is still green. Keep the tubers cool, as previously advised.

When catering for the early market it is not advisable to plant large seed ; small tubers will produce the earlier crop. In.late wet districts, or where the land does not come into a friable and nice working condition very early in the spring, it is advisable to box the seed. Sprouted seed may be planted later, and then be just as early as if it had been planted in the best condition a month before. There is thus a relief to the pressure of spring labour, and it is also a relief to the farmer’s mind to know that he need not battle with sticky land.

Seed should not be boxed all winter, as the sprouts get too long — that is, for the main crop. It is better to put -potatoes to sprout about two months before they are required for planting, and keep them in a cool place until then. If the sprouts get knocked off fresh ones will appear, but they are not as -vigorous as the first ones.' Under rough-and-ready methods of planting, and where the land is under an indolent method of tillage, it is best to put in unsprouted potatoes.

It is always advisable to test the germination of seed-potatoes. Put a small quantity in a warm dark place to sprout two months before planting-time, in order to see if they all sprout well. Look carefully for tubers with sprouts almost as thin as cotton. Such tubers are affected with spindle-sprout disease, and wherever one is planted there will be reduced profits.

ROTATIONS AND YIELDS.

Where should the potato, come in a rotation ? Certainly, for preference, after a leguminous crop or a pasture in which clovers have formed part ' of the herbage. Potatoes are not hard on the soilthat is, they do not remove large quantities of its fertility. Many farmers in certain districts of - England follow potatoes with autumn-sown wheat. Quite as good crops of grain have been grown following potatoes as from summer fallow. In Jersey an early-maturing spring wheat often follows the early potato crop, and it is not uncommon to see the Jersey mangold being sown immediately the crop of potatoes is off the land. A rotation I know of as having been successful was lucerne four years, potatoes in the fifth year, and the sixth year wheat. When lucerne-seed can be bought at is. 6d. per pound it is not a costly crop to grow so far as seeding is. concerned, and where lucerne does well potatoes also do well. The heaviest crop of potatoes ever raised at Moumahaki Experimental Farm followed lucerne. Peas and vetches are good preparatory crops for potatoes. Crimson clover sown in early autumn and ploughed or dug in during the winter is also a good preparer.

Under good cultivation, following a legume and given favourable weather conditions, it is quite possible to get 30 tons of potatoes per acre. To set about it, space the rows 26 in. apart, equivalent to thirty rows in a chain. • Space the sets in the row 12 in. apart. There will then be required 19,800 sets to plant an acre. If the sets weight 2 oz. each it will take 1 ton 2 cwt. 11 lb. of seed to plant an acre. Estimating the average yield per plant to be 3-4 lb., 19,800 plants X 3-4 lb. gives 30 tons per acre. Some of my seedlings at Weraroa this year have yielded more than 3-4 lb. per foot of row.