Primary-P matches DAP/MAP in boosting maize yields

The dry matter yield of forage maize crops can be significantly improved if phosphate is applied with the seed at the time of planting, according to trials performed by Kingshay.

The trials, performed in 2010, 2011 and 2012, sought to replicate on-farm scenarios with the land receiving a typical application of either slurry or farm-yard manure prior to crop establishment.

In keeping with typical farm practice the trial used phosphate as either monoammonium phosphate (MAP) or diammonium phosphate (DAP), depending on which was cheapest when the trial commenced.  In 2010 this was MAP while in 2011 it was DAP. Although DAP has a greater nitrogen content this was not regarded as significant to the outcome of the trial due to the volume of manure applied prior to planting which would mean the crop would enjoy a plentiful supply of available nitrogen.

While demonstrating the benefit to crop output from applying phosphate at the time of the planting the trial also sought to evaluate the performance of  a micro granular starter fertiliser called Primary-P from De Sangosse which also contains a protected phosphate treatment named PPT.

Two rates of DAP/MAP were investigated (125kg/ha and 62.5kg/ha) while Primary-P was applied at the standard application rate of 20kg/ha.  In all cases, plants which received Primary-P produced a similar performance to plants treated with DAP/MAP despite the significantly lower application rate. Perhaps not surprisingly, all crops recorded a statistically significant improvement over the untreated control crop.

Samples from each trial were taken and analysed for nutritional quality, but no significant differences were determined between treatments.  This suggests that the principal benefit of applying phosphate at planting is restricted to yield.

Crop yield under differing phosphate regimes (mean of trials)

Treatment Fresh yield (t/ha) Dry matter (%) Dry matter yield (t DM/ha)
 Primary-P (20 kg/ha)  51.30  31.45  16.12
 DAP/MAP (125 kg/ha) 51.84  32.27  16.55
 DAP/MAP (62.5 kg/ha)  47.32  31.50  14.92
 Control  46.56  31.55  14.54

Source: Kingshay

Reviewing the results Kingshay senior technical specialist Dr Peter Shipton who oversaw the trials said the performance of Primary-P was likely to be of great interest to growers and contractors.

“Only having to apply a sixth of the volume compared to DAP/MAP at 125 kg/ha yet achieving similar levels of performance could offer an efficiency gain from having to transport and load less product between fields. As Primary-P is delivered in a bag size of 10 kg it also removes the need for a loader as the operator can load it by hand.

“This could save time at what is a very busy time of the year for growers and contractors as Primary-P could be used in place of a standard fertiliser and yet deliver comparable yields,” he added.

De Sangosse commercial director Kim Christo said the benefits of Primary-P at planting confirmed what had been seen in other parts of Europe where this is a standard treatment. Also there was “growing interest” in many other crop types in the UK.

“We know from trials performed with oilseed rape that phosphate applied as a protected micro-granule is more available to the young crop than when applied as standard fertiliser. This has been reflected in considerable improvements to establishment, vigour and yield.”

The trial was due to be repeated in 2013, but had to be abandoned as poor weather at the time of planting led to the crop failing to produce an even plant stand. In the interests of statistical rigour it will be repeated in 2014.