I have trouble growing new potatoes. I’ve tried rotation, fertiliser, a variety of seed potatoes, but to no avail. When time to cultivate after flowering, they are the size of small marbles. What could be the problem?
You have obviously tried very hard to cultivate a good crop of potatoes. There is one thing you have not mentioned – the mounding up of soil as the young potatoes come into maturity. As they commence growing, and when plants are about 20cm high, regularly ‘mound up’ the soil up to around 10cm above existing ground level - on both sides of the plant, weekly or fortnightly. You can even cover some of the new shoots and lower leaves as this will help towards a better crop. This “‘mounding up’ process helps warm the soil around the roots of the potato plant which contributes to better development of reasonably sized potatoes.
There is also a possibility that your soil could be either too heavy or poorly drained, or in the other extreme it is very light and porous therefore not retaining sufficient moisture as the potatoes are developing. A good application of Daltons Compost will help in either situation.
Do continue the rotation of your crops in your garden and try not to grow potatoes where either tomatoes, potatoes or sweet corn have been growing in a previous year.
As the potato plants develop, apply a light side dressing of a good quality potato fertiliser like Daltons incredible edibles® Potato Fertiliser which is specifically formulated for all potato and kumara varieties. Do not add any high nitrogen fertilisers to the plants at any stage as this will lead to development of large top growth with very small potatoes.