New research has hinted that consistent seed spacing may not influence final saleable potato yield as much as first thought and could spell the end for cup-type potato planters.

A project by NIAB-CUF PhD researcher Simon Smart has been assessing the effect of seed spacing on the crop and initial results from the first year have made some interesting discoveries.

“Work has shown that the variations from the target seed spacing may not be impacting too badly on crop performance, so we may have to question what our priorities are for planter performance,” said Mr Smart.

More on potato establishment

However, he pointed out that it was still vital to ensure that the right numbers of tubers were planted on a wider scale, using the correct seed rate.

Growers have guidance on seed rates and target plant populations for each variety grown commercially in the UK, and the aim is for the crop to be as uniform as possible.

“We are just trying to quantify what we mean by accuracy and how much we can trade for speed in our planting operations,” Mr Smart told delegates in a workshop at the Cambridge University Potato Growers Research Association (CUPGRA) conference.

Planting density affects the number of stems produced in the crop – dictating canopy development, tuber numbers and subsequent saleable yield.

From Mr Smart’s observations in a crop of Maris Piper last year, he believes that when a seed drops too close to its neighbour it naturally grows away from the shade into the gap left behind.

“Work has shown that the variations from the target seed spacing may not be impacting too badly on crop performance, so we may have to question what our priorities are for planter performance.”
Simon Smart, NIAB-CU PhD researcher

This gives both plants adequate space and they are able to produce a yield much closer to that of two evenly-spaced plants.

“This will vary between varieties, with Maris Piper being one of the more ‘plastic’ varieties that has a greater ability to compensate,” explained Mr Smart.

Cup planters pick up individual seed tubers out of the machine’s hopper and are generally perceived to be the most accurate for seed placement.

Barry White, UK managing director of potato machinery manufacturer Grimme, said that just five years ago cup machines made up all of their planter sales.

However, belt-fed planters which deliver seed to the ground directly from the hopper can double work rates in the right conditions due to higher forward speeds, but are not as accurate.

Belt planters now represent 80% of the company’s planter sales in the UK and are becoming increasingly attractive as there is a shift towards bigger farm sizes and extreme seasons have caught growers out at planting time, so timeliness is key.

Mr White said it would be extremely useful to quantify the level of accuracy belt planters could lose before they have an adverse effect on crop density and yield.

“They have such an advantage in speed over cup planters, but if there’s no significant penalty for sacrificing accuracy, maybe we wouldn’t need to build any cup planters whatsoever,” said Mr White.

Mr Smart said research would continue with a range of varieties next season.