How soil analysis can improve productivity and reduce costs

• Tests boost soil health and sustainability

• Role of soil carbon increasingly important

• Greater insight boosts natural resources 

Growers looking to get more out of their soils and improve productivity should start with a field-by-field nutrient analysis, say experts.

Soil testing and tissue analysis of growing crops and harvested grain can improve soil health, optimise nitrogen use and deliver greater long-term sustainability, says Allison Grundy, agronomy manager with independent specialists NRM.

“Detailed soil nutrient analysis, including an assessment of spring nitrogen, should be carried  out every year if growers are to use nitrogen and other key nutrients such as phosphate, potash and magnesium, as efficiently as possible.”

Optimal nitrogen

“Calculating optimal nitrogen applications means estimating the soil nitrogen supply as accurately as possible alongside a realistic target yield.”

Over-estimating yield by 1t/ha when calculating nitrogen requirements, for example, could result in applying 25kgN/ha more than is necessary.

“A key aim should be to make the best sustainable use of the resources nature provides before nitrogen is applied. If we are to get fertiliser applications as low as feasible, all factors t have to be considered.

“A good soil structure is vital, so plant roots can scavenge for soil nutrients.”

When it comes to soil carbon, NRM’s CarbonCheck soil carbon test kit is increasingly in demand, say Ms Grundy.

“Knowing soil carbon content is essential for the Sustainable Farm Incentive (SFI) applications, but that is only part of the story.”

Soil carbon content links the physical, chemical and biological processes in the soil, which is why it is so important in the improvement of Nitrogen Utilisation Efficiency (NUE) and better uptake of other key nutrients such as phosphate, potash and magnesium.

“It also has implications to soil structure, moisture retention and healthier soil biology with carbon driving the overall functionality of the soil.

“In fact, there’s a direct relationship between soil carbon content and productivity so it’s an essential element in understanding soils better and improving their long-term resilience.”

Knowledge gained from soil nitrogen and carbon testing can then be further enhanced by taking tissue samples in the growing crop around growth stage 30-31, says Ms Grundy.

Criticial test

“Our CropCheck analysis is a growth-stage critical test that gives you an accurate insight into what is happening in the crop.

“If, for example, some indices are sub-optimal, growers can do something about them before it is too late and they start affecting crops yields and quality.

“Adverse weather and crop conditions between the initial soil nutrient testing at the start of the year and the rapid growth phase in the spring can change predictions of crop nutrient requirements significantly.

“But there all manner of soil biology and nutrient interactions that can also affect how well the crop is taking up nutrients and you will only know this if you have a good insight into what is happening in the plant.”

NRM’s GrainCheck is the final test of the growing year and is used to check the nutrient content of grain after harvest, explains Ms Grundy.

“This is another good indicator of the crop’s ability to extract nutrients from the soil and if levels are low it can point to problems not just with nutrient applications but also field conditions and soil structure.

“If the soil is too compacted, for example, root development is adversely affected, biological activity is reduced and nutrient uptake, especially phosphate, is restricted.  If soil pH has dropped too far, it will also reduce the availability of key major nutrients apart from trace elements such as manganese.”

Grain nitrogen content can also provide a good indication of likely fertiliser requirements for the following year.

Grain analysis

“Weather and soil conditions over the following winter months will impact again on the availability of soil nutrients the following spring but grain analysis can give a valuable early warning of any looming issues that need to be addressed.

“The actual soil nitrogen supply (SNS) will then be ascertained with N-Check analysis the following Spring and the cycle begins again.

“Ultimately it’s about managing soil to the yield potential it can deliver year-in year-out without completely battering the resources available on the farm.”