Planting and Cultivation
Quick, even emergence and good early crop growth are essential in the quest for good yields of quality potatoes.
Where grass is ploughed up it is recommended that grass is burned off in advance of ploughing using Glyphosate. Deep cultivation (down to approximately 25 cm) is an essential start to seedbed preparation.
The aim of subsequent cultivations is to provide a fine seedbed with 12 - 15 cm of clod free tilth. Loose cloddy seedbeds will dry out, causing slow growth, irregular emergence and low stem counts. Wait until soils are dry enough, and then use an appropriate implement for cultivation.
Cultivating soils that are not dry often results in compaction, and damage to soil structure. This restricts the rooting capacity and subsequent yield of the potato plant.
Ploughed ground is usually cultivated with a heavy tine cultivator prior to bed tilling and ridging. Bed tilling and ridging involves cultivating the soil to a depth of 15 -18 cm, and leaving it in large ridges between 175 – 185 cm in width.
A firm fine seedbed is essential for planting
Stone separation is the process of removing stones and clods from the formed ridges, and burying them between alternate rows. This substantially reduces tuber damage during harvesting, and greatly increases harvester output.
The ridges should have been adequately cultivated prior to stone separation to ensure there are no excess clods to be removed. Soils need to be dry to ensure good separation whilst also avoiding damage to soil structure.
Certified seed should be ordered and purchased from an approved source. The use of uncertified seed may lead to virus and fungal disease outbreaks.
The Department of Agriculture operates a seed certification scheme:
Seed potatoes need to be stored over winter in a refrigerated store at 4°C to prevent over-sprouting. Poor storage of seed results in excessive sprouting and sprout breakage which in turn leads to:
- Poor crop vigour
- Irregular germination
- Wide range of stem numbers
Chitting is the controlled production of sprouts on potato tubers. This is done to bring forward harvest date and to increase yield and quality. More and more main crop producers are chitting their seed for early maturity, and to lengthen the harvest window. In chitting, light and temperature are controlled to ensure the production of 1cm long strong sprouts.
Time of Planting
The optimum planting time for maincrop potatoes is March - April. As a general rule planting should not take place in unsuitable soil conditions, i.e. soils which are cold and wet. Ideally, soil temperatures should be around 70C for three consecutive days before planting. In areas where frost is a risk (i.e., inland, low-lying areas) sowing after mid-March reduces the risk of frost damage to the crop.
Depth of Planting
Potatoes should planted at a uniform depth of about 12-15 cm below the surface of the ridge and 4 cm above the base of the furrow to protect the seed in wet periods. Very small seed should not be planted too deep, as it may struggle to emerge and be less vigorous. Some varieties e.g. records need to be planted deep (below 10 cm) to avoid greening.
Seeding Rate and Spacing
Seeding rate depends on what spacing is choosen between the ridges and the distance between tubers in the same ridge.
A ridge width of 80 cm is recommended, but row widths of up to 90 cm can be used.
Wide rows have certain advantages:
(a) More weathered or cultivated soil is available to make a good ridge.
(b) The sides of the ridge are less likely to be compacted by tractor tyres, thus reducing clod formation and tuber greening.
(c) Faster work rate when planting the crop.
Research generally indicates that row width of up to 90 cm has little or no effect on yield providing that the seeding rate is not altered, i.e. seed is planted closer in wider rows.
Seeding rate is important for two main reasons:
(a) Seed is a major cost item and therefore must be used effectively.
(b) Seeding rate has a large influence on the size of the tubers produced, and so must be adjusted to suit market requirements.
Split grading of seed, 35 – 45 mm and 45 – 55 mm is advisable to facilitate easier planting and accurate spacing of tubers. Split grading of seed will produce a more uniform crop. Seed size should match the capacity of the planter cups. Plant at the correct speed to obtain accurate placement. Ensure that the planter is in proper working order. Spot checking of the planted drills and the planter, on an ongoing basis, is necessary to ensure accuracy.
Optimum Spacing for Maincrop Potato Varieties - Planted in 80 cm rows
|Records||Kerr's Pink||Golden Wonder|
|Small seed (35-45mm)||20-25cm||20-25cm||20-25cm|
|Large seed (45-55mm)||28-33cm||28-33cm||28-33cm|
In wider rows, the spacing between tubers should be reduced to maintain the seed rate per hectare. For example, if the rows are 90cm apart, then plant small seed (35-45) at 17-21 cm spacings. The optimum seed rate and seed spacing varies greatly depending on the type of production (i.e. the size of tubers required), variety, conditions of growth and the cost of seed. To increase tuber numbers and reduce tuber size, increase the seeding rate with larger seed and /or closer spacing. Do the reverse to reduce tuber numbers and increase tuber size i.e. small seed with wider spacing.
If placing fertiliser at planting time ensure that it is positioned 10cm away from the tuber to avoid scorching. Fertilisers can be reduced by 20% if placed in the row.