Drilling with a starter fertiliser helps root development

Fertiliser down the spout with the seed may be the way forward for autumn sown cereals


Soil nutrient levels have been subject to much discussion and these days more than ever is known about the status of field indices due to the increasing practice of soil sampling and so individual decisions regarding fertiliser usage can be made, not just on a field by field, but on a zone by zone basis across the farm depending on the crop being grown and the intended market for it; for example, malting barley or milling wheat.

Soil is made up of four distinct elements – namely the soil reserves (organic matter and minerals), air and soil water and, between them; there is a permanent interchange of nutritional elements. Nutritional elements will be taken up by plants via the soil solution (nitrogen, potassium) or by direct soil-root contact (phosphorus) and whereas nitrogen and phosphorus have the strongest effect on the development of seedlings, potassium can alleviate the negative impact of compaction as well as unlocking nitrogen uptake and improving frost resistance of the crop. Phosphorus is very immobile in the soil but is fundamental when it comes to promoting rooting and so the crop has its biggest requirement for P during the autumn growth stages. Nitrogen, for a lot of the time, is available in sufficient quantities because of residues from the previous crop. We can make a distinction between nutritional elements in such that we have either macro-nutrients (e.g. nitrogen, phosphorus, potassium …) or micro-nutrients (e.g. manganese, boron …) with these micro-nutrients often being applied in micro-granular format or as a foliar feed.

It is also important to decide on a strategy for phosphate and potash use. For example, are we trying to build up soil reserves, maintain existing levels or run down levels in what can be called a ‘nutrient holiday ‘and so soils should be rechecked every 3 – 5 years to see if status quo is being maintained. If farmyard manure is being used then the available nutrients provided by any application need to be calculated - as does the amount of phosphate and potash being removed by the crop according to yield and also whether straw is being removed or retained on the field. RB209 is the best source of information with regard to working out the required rate for each nutrient.

The conventional methodology of full width application using a granular fertiliser broadcaster is designed to top up both the soil reserves and soil water and the emerging crop competes with microbes, weeds and minerals for these nutritional elements. Nutrients held in the soil solution can be accessed by the crop more readily than nutritional elements held in the soil reserve and so utilising this information, nutrient maps can be prepared and then the site-specific application of base fertilisers can be carried using precision farming techniques.

“Starter fertilisers” accelerate seedling development
Early supply with essential nutritional elements means immediate accessibility of the radicles and is ideal for promoting the development of a strong root system. By accelerating seedling development by the use of a starter fertiliser, then the crop is strengthened against diseases and pests and it improves the competitive edge against weeds. Cold, wet soils tend to slow down root development making nutritional elements more difficult to access and in a reduced tillage scenario, due to more surface trash and more moisture, soils tend to be colder than with conventional tillage thus meaning that a starter fertiliser could be even more important.

The principle behind applying fertiliser at drilling is to target applications close to the seed. This allows lower rates to be applied as there is a higher concentration of nutrient closer to the seed and growers will use it also as a method of saving fertiliser. Phosphate benefits most from this method due to it being very immobile within the soil compared to nitrogen and potash and the result is an improvement in crop establishment as wells as an increase in the efficiency of nutrient uptake. However, and depending on cropping, care needs to be taken not to get some fertilisers too close to the seed as high nutrient concentrations close to the seed could impact germination with small seeds being even more at risk of suffering germination issues

Combined grain and fertiliser seeding can be split into two distinct scenarios which, in AMAZONE speak, are known as SingleShoot or DoubleShoot:

When we look at Single Shoot, where the fertiliser is placed down the spout with the seed into the seed furrow, this offers advantages - regardless the soil fertility and soil quality - as the risk of suffering locally from a lack of nutritional elements by direct contact to straw is counteracted by the additional fertiliser. The crop is competing with the microbes that need, amongst other things, nitrogen from the soil solution to break down straw, referred to as Nitrogen lock up, where there is an imbalance in the Carbon/Nitrogen ratio.

Combining the two jobs of fertilising and drilling can save time although the capital cost of the equipment used can be greater and the hopper sizes are reduced meaning different filling logistics and turnaround times but the improved early development reduces costs for crop protection and this technique is ideal for winter oilseed rape using DAP or MAP but for winter wheat/barley only using TSP due to restrictions on the use of autumn N.

The trend to wider row widths (e.g. 16.6cm) gives an increased banding effect and so to an even higher concentration of good available nutritional elements in the seeding zone and thus the rate of fertiliser can be reduced. Germination issues increase with increasing application rates which, depending on product, can vary from 125kg/ha product to 250kg/ha and lack of moisture is by far the biggest factor as to whether germination damage will occur. If you can’t wait for sufficient moisture or reduce the rate applied, then it is best to switch from an ammonium-based fertiliser to a Superphosphate based product. The time seed and fertiliser are in direct contact should be minimised as much as possible; DAP and MAP both contain ammonium N and this can cause more damage than Superphosphates (TSP) and plants that respond well to nitrogen can compensate for damage levels of 15 – 30%.

This system is available on the AD, AD-P and Avant drill combis, the rigid Cirrus 4003-C; the folding Cirrus 6003-2C, Cayena 6001-C; Citan and Condor 12001-C / 15001-C drills in the AMAZONE range.

Independent application of fertiliser down a separate coulter
Known by AMAZONE as DoubleShoot, this is the separate placement of seed and fertiliser into different soil zones with the distance between seed and fertiliser at a minimum of 2cm and this technique is used for instance in maize establishment or for potatoes in conjunction with a bed system. The amount of fertiliser applied tends to be higher than with Single Shoot at around 100 – 400kg/ha and can be used effectively also with spring cereals in conjunction with a second application of N and can be fitted to the AD, AD-P and Avant power harrow / drill combinations.

The use of starter fertilisers along with cereal crops continues to look promising in terms of producing a crop that is capable of withstanding the rigours of both wet and dry extremes by stronger rooting systems as well as out-competing grass weeds earlier on in their life-cycle and the highly effective grain and fertiliser transfer systems found on the C range of Amazone drills, both in drill combi format and trailed high output drills such as the Cirrus C or Cayena C drills, can maximise the benefits of grain and fertiliser seeding. Let AMAZONE look after your acres.