SPoT trials point to saving planting costs

POTATO growers across Scotland could save money, man hours and boost production by reducing tillage prior to planting and applying lower rates of nitrogen. 
That was the message given at a recent meeting of the AHDB Strategic Potato Farm Programme (SPot project) at Bruce Farms, near Meigle, Perthshire, where results from the second year of trials at the farm were revealed. 
“We’re absolutely delighted with this year’s results,” said AHDB Potatoes’ knowledge transfer specialist, Claire Hodge. “Research into cultivation methods has proven that reducing cultivation depths can not only save time and costs but also increase yield and quality.” 
Four separate plots of Maris Pipers were planted using different cultivation techniques, including the standard farm practice of 12-inch bed-forms, bed till and de-stone depths; bedforming and destoning at 12 inches and reduced bed till at six inches; bedforming at 12 inches and destoning at 10 inches without bedtilling; and triple bedtilling followed by destoning at 12 inches. 
The trials showed that by adapting systems from a till-all approach to reduced cultivation in using just the triple bedtiller, followed by the destoner, reduced planting costs per ha by more than £20 and increased tonnage per ha by 15 tonnes.
Kerr Howatson, potato manager at Bruce Farms, said that although the triple bedtilling was not the cheapest technique out of all four methods – having cost £59.21 per ha – it did outdo the rest in terms of producing quantity and quality. 
Producing a total yield of 43.38 tonnes per ha, with planting costs per ha of £59.21, the triple bedtiller method also gave the highest packout figure at 75.01%. This compared to 52.89% and 28.33t/ha for the farm standard, 61.35% and 34.53t/ha for the reduced bedtillage plot, and 57.75% and 33.03t/ha for the no bedtilling plot. 
Meanwhile, planting costs per hectare for the farm standard technique was £82, with reduced bedtill at £77.32 and the no bedtill plot costing £45.53. Labour costs were also significantly reduced at £30.84 per ha when using the triple bedtiller, compared to farm standard at £52.20 and reduced bedtill at £49.79.
NIAB’s Dr Mark Stalham, also praised the triple bedtiller and said that he planned to trial it again. “The triple bedtiller can work at different depths rather than one fixed depth, so this allows the operator to work against different soil levels. If you have an investment of this kind you want to see it work and produce good results, so we will keep it in and test again.” 
In terms of cultivation depths, Dr Stalham said that there were yield benefits to be had from ploughing and planting at shallow depths depending on the type of soil used.  
“Our soils are becoming increasingly difficult to cultivate because of bigger, heavier types of machinery. If you work with soils that have a high clay content, you’re going to cause damage, while shallower sandy soils could result in yield loss. 
“There is no benefit to deeper ploughing, but there is a gain to working at shallower depths around 1-2 inches both in terms of yield and costs of production,” he added. 
Further testing in the trials also showed that huge savings can be made when applying nitrogen in the planting process and by cutting out on top dressing all together.  
“A lot of potato producers often apply the top dressing as an insurance, but it could actually be compromising production. Regarding nitrogen applications, you need to take your winter rainfall and seed variety into consideration to estimate the amount of nitrogen needed,” explained Ms Hodge.  
Each of the four plots of Maris Pipers received 147kg per ha of N in the planting process and then three of the plots were given 29kg of N as a top dressing in standard form, liquid form and by ridge injection. Ultimately, the plot that received no top dressing had a yield of 40.88t/ha, which was four tonnes more than the ‘standard’ method and produced the highest packout figure of 67.62%.
Results for the other trials saw 64.88% and 36.05 tonnes achieved for standard system, 64.58% and 37.47 tonnes for liquid form and 62.89% and 37.76 tonnes for the ridge injected plot.  
The project also looked at the benefits of cover crops and their potential to improve conditions throughout the winter time. Despite increasing planting costs, Mr Howatson said that since planting cover crops in 50 acres of low lying heavier soil, soil structure had been improved.