Managing the nutrition of second wheats

When it comes to managing second wheat crops there are some key management techniques that can help increase crop yield. To make the correct decisions first consider what the key constraints to growth and development are. Successful yields, as research has shown for decades, come from crops with high biomass. The question then is how we improve the biomass that is very often low in second wheat crops due to later drillings and lower nutrient supply. The lower nitrogen supply is often exasperated by poor root systems that are the result of ‘Take all’ infections.

The lower soil nitrogen supply needs to be managed in two ways, firstly the total amount applied needs to be 40 kg N/ha more to balance soil supply and crop demand. Secondly, with crops wanting to grow away as soils reach 4-5 ^oC, then prioritise nitrogen applications to ensure spring regrowth gathers momentum. These early applications will encourage tillering, and with increased tillering comes more roots to help compensate for those damaged by Take all. Research by HGCA (now AHDB) clearly highlighted that early nitrogen management was the key to success. This research also concluded that putting higher rates on early was also critical. In the experiments, the highest yields came from where 40% of the total nitrogen dose was applied in the first application window (i.e. Feb/Early March).

Within this research the components of yields were assessed and again using the 200 kg N/ha as an example the data highlighted the effect high rates or early nitrogen had on the shoot / m2 (and therefore crop biomass). This effect translated through as anticipated to higher yields

A greater proportion of nitrogen needs to be applied earlier

One of the key components to achieving high biomass crops in May, June and July is the management of the early foundation stage of crop development. A Yara crop nutrition strategy can be used as a remedy, helping to recover some of the lost yield potential. Such a strategy requires a combination of actions to increase early spring growth rates, involving fertiliser and foliar-applied nutrients. When the soils start to warm up, and reach 5 ^oC crops will begin to grow again, however, the nutrients (N, P, K and S) will be at their lowest availability, especially in the rooting zone. The first spring management action is to apply an appropriate fertiliser (late February) to meet this nutrient demand. The phosphate source is particularly important and needs to be one that is NOT immediately ‘locked up’ (TSP, MAP, DAP based fertilisers), and gives season long, continuous supply (YaraMila with P-Extend).

Foliar application of phosphate gives an ‘energy boost’ to the crop

Considering the root biomass and effect that ‘Take All’ has on it then it is also important to make appropriate management decisions that can minimise the impact of this on Nitrogen Uptake Efficiency, the first component of achieving high Nitrogen Use Efficiency.

Firstly, consider how the root system can be repaired, or improved to enable better access to nutrients that are available.  One way of repairing and building a larger root system is to apply some phosphate through the leaves. Research has shown that an application of foliar phosphate at GS 25 – 29 can significantly increase both root size and area. The recommendation is that YaraVita Magphos K (NOT phosphite) should be applied to the growing crop to give it a ‘boost’ of energy, accelerating the early spring growth.

This foliar application of phosphate gives an ‘energy boost’ to the crop, stimulating the growth of roots and consequently shoots. Not only does this give an immediate benefit by way of recovery/repair, it builds in resilience, enabling the crop to overcome further potential stress points such as drought during the spring and summer months.

Secondly, it is important to consider the soil nutrient supply and how this needs to be managed. Such an injection of growth through the foliar phosphate application will of course create further demands on the soil nutrient supply to satisfy this new growth. There is the potential that the cold wet soils have a very limited pool of available phosphate that will be quickly exhausted. Therefore to ensure the new growth momentum continues, supply some fresh soil-applied phosphate such as a YaraMila Actyva S

This combination of a YaraVita foliar phosphate product along with an application of YaraMila soil-applied phosphate will energise the crop for early, rapid spring growth and development to recover and build biomass for an improved grain harvest. Indeed, trials results have shown wheat yield increases from 0.23 – 0.6 t/ha. (Yara internal trials, 2011).