More parameters in soil testing pays off

9 December 2021

New techniques make extensive soil testing feasible and affordable for practitioners. A recent large-scale study in Germany shows that more parameters enable further crop optimization. "The large amount of data makes this a unique study," says Arjan Reijneveld, International Product Manager Soil at Eurofins Agro.

Due to the introduction of new techniques, such as NIR, it has become possible in recent decades to measure many soil key figures quickly and relatively cheaply. With all these parameters it is not only possible to gain insight into soil health, soil fertility and the amount of carbon storage in the soil, these parameters also help to optimize the cultivation.

Routine soil testing in many countries consists of only a limited number of key figures. In Germany, P-CAL, K-CAL, Mg-CaCl2, and pH are the common determinations in soil testing. In contrast, the standard soil analysis in Fertilization Manager from Eurofins Agro consists of more than twenty parameters. Together, these parameters provide a complete picture of essential nutrients, soil physical characteristics, biological characteristics, and organic carbon.

A recurring question is, do all those extra key figures deliver? A recent study in Germany together with Thomasdünger (later Arbeitsgemeinschaft Hüttenkalk EV) shows a clear picture.

The study

The study used a large amount of data from German field trials over the past twenty years. The soil samples from these trial fields were analyzed again for the four German key figures and additionally for twenty parameters with Fertilization Manager. The crops in the study were potato, sugar beet, winter rye, winter wheat, spring barley, rapeseed, winter barley, mixed wheat and alfalfa. Data of fertilizer management, precipitation, yield, location, field and yield were available.  

The analysis showed that with limited research (four key figures) the differences in yield could be explained with an average of 43%, while BemestingsWijzer this was 72%. When rainfall and fertilizer applications were included, the prediction of expected yield was found to be even better; 65% in the case of the routine survey and over 80% with Fertilization Manager.

If the soils were divided into 'high' and 'low' soil fertility, the average yield on the soils where the soil fertility is higher (partly by nature, partly by management) turns out to be clearly (significantly) higher. Take potato, for example. Soils with higher fertility gave on average more than 15 tons higher production per hectare per year in this study.

More parameters pay off

Researcher Arjan Reijneveld says, "This research in Germany was unique because we could use large amounts of data. Both soil key figures and climate and yield data were available."

"Combining twenty soil chemical, physical and biological characteristics resulted in better yield predictions than were possible based on four parameters. These key figures can be used by a farmer/grower and specialist to guide. Some strategies will pay off immediately (annual level) and others will take more time (rotational level or longer).  For example, increasing effective CEC by improving pH is relatively quick. In doing so, the exchange capacity of K and Mg increases and the crop has more nutrients at its disposal.  Other investments in, for example, soil structure and organic matter content obviously take more time.