What role do starter nutrients play?
Following the overview of the nutrient requirements of maize and the technical consideration of fertiliser application, the third part of the solid/liquid fertiliser series deals with the effects of starter nutrients on plant development - based on extensive tests.
In order to gain relevant insights, extensive tests were carried out at various sites with the objective of obtaining answers to the following key questions:
- How can traditional DAP underground fertilisation be complemented or carried out with reduced quantities without losing yields? Can the absolute amount of underground fertiliser be reduced by a targeted liquid fertiliser as a complement to DAP - while maintaining the yield level? DAP was tested with an NPK solution in various quantities and reductions.
- Are there differences between pure nitrogen (AHL) and NPK solutions? In this test, pure liquid fertilisation was used.
- Can the yield level be stabilised in the event of weather extremes or difficult conditions? Can the crop be given more vitality in the field by targeted fertilisation to be better prepared for periods of heat and lack of water? These questions were examined in a version with DAP and an NPK solution.
- The traditional solid fertiliser contact fertilisation by means of DAP directly into the row (without additional liquid fertiliser) is also part of the test series.
A specially adapted machine was used for this purpose. Several liquid fertiliser hoses were mounted on a 6-row Maestro TV with a variable frame: for liquid underground application, for an application in the row directly at the grain as well as for fertilisation next to the row, but in the grain root area of the maize. The machine was also equipped with a solid fertiliser tank for classic underground fertilisation with DAP. A Leeb 1.4 CT was mounted in the front – a separate front tank with its own pump and control system for the application of liquid fertiliser. This machine setup was specially designed for the test series. However, similar equipment is already available for various Maestro models such as the SV/SX, the SV L/SX L and the RV and is also planned for other models in the future.
Sites and prerequisite
The tests were set up in different regions: in the Czech Republic at a no-till site with heavy soils, in Styria (Austria) and Alsace (France) on very good maize sites with a warm climate and in the Schwandorf area as well as directly at Sitzenhof at sites with a medium yield level. The tests, thus, cover a wide range. The sites were not selected with the aim of being complete, but with the objective of capturing a good cross section. Seeding was carried out between 10th and 24th April – corresponding to the usual dates in the respective regions. At the time of seeding, there was sufficient water in the soil in all fields. Rain came early. It then was dry in many regions - in some cases four weeks without any significant rainfall. All in all, water availability varied considerably. Spring 2025 was rather cool at all sites. At the end of May, temperatures partly were still below 10 °C at night and even dropped to 2 °C in some regions. It was warmer at times during the day, but overall temperatures were below average for this time of year. Good conditions, therefore, for making the effects of targeted starter fertilisation visible in a cool year.
Observations in the population
Initial findings were already evident in the populations at a very early stage. With pure AHL fertilisation - if no additional phosphorus was applied - the plants turned bluish-purple, as expected. The effect was even intensified by the cool temperatures. Even on sites where liquid manure was applied in advance, i.e. where there actually was enough phosphorus, the plants changed colour because the phosphorus was not available to the plants because of the cold soil temperatures.
The varieties fertilised with liquid NPK developed very well. No bluish discolouration could be noticed. Despite the low temperatures, the applied phosphorus was available in the seed row. Up to the 4- or 5-leaf stage, the plants grew significantly better and, in comparison, were already somewhat larger and stronger. DAP contact fertilisation directly in the row showed similar effects. Here, too, the typical blue colouration did not occur. Also with classic underground fertilisation, the plants did not show any discolouration. However, you could see that it took a little longer for the fertiliser in the depot to be absorbed by the root system. But the difference compared to the liquid fertiliser versions quickly disappeared as the plants grew. With higher quantities of liquid fertiliser - both AHL and NPK - grain burns occurred. They were provoked deliberately to be able to make better statements about when a burn occurs and the limit of the application quantity is reached.
The input of liquid fertilisers directly into the seed furrow is referred to as contact or starter nutrient input, i.e. as supplementary fertilisation. It became evident that the basic supply of the plants with nutrients has to come from underground fertilisation, liquid manure or the nutrients present in the soil. Pure contact fertilisation (liquid or solid) cannot replace the basic supply of the plants with nutrients as the grain and the seedling would be burnt by excessive amounts of fertiliser.
Outlook
The tests will continue to be monitored over the summer. The focus will be on the differences in yield and the question of whether the early differences in development are reflected in the yield or whether they fade again as the plants grow. Further evaluations will be available at the Agritechnica in November - where we will also present technology for targeted liquid fertilisation and discuss the topic with the visitors.