EEHNC presentation: Questions and Answers

At the EEHNC's first day on March the 25th, Karst Brolsma gave a presentation on: 'General considerations for forage & pasture management: What factors affect the nutrient content of pasture & forage?' During the presentation a number of participants asked questions. Below you can find these questions and the answers provided by Karst Brolsma. 

 

How can fertilization or the soil fertility impact the oxalic acid concentration on C4 Grasses (Pennisetum sp./ Pannicum maximum)?

For oxalic acid, there is a possible link. What I showed in the PowerPoint is the coupling between Sulphur supplying capacity, organic carbon/organic matter ratio and organic carbon/nitrogen ratio in soil with amino acid composition of grass. So I would suggest that there is a link between oxalic acid and soil fertility.

 

What is the Se condition of Dutch/European soils and is NIRS possible for determination of Se?

Selenium cannot be measured by NIRS, we measure it after soil extraction with CaCl2. On average we see Se levels in grasslands of 4 g/kg.

 

How beneficial is it, to put limestone on the horse fields (to reduce acidity of the field)?

Very relevant. With limestone you increase the soil pH and you apply calcium, both are good for soil fertility. Be aware of the type of soil here, limestone on clay soils with high pH does not work very well. Here you could use gypsum instead.

 

Are you seeing, or do you anticipate, an effect of Global Warming on micronutrient content in soil (EU / UK), for example, based on increased adverse rain events or soil pH?

Yes. Drought is affecting the availability of nutrients. We saw an increase in potassium under drought conditions. Also dry weather is reducing the turnover of organic matter and as such lower nitrogen and Sulphur levels in a soil.

 

Every week we get a question from a horse owner that has done a soil research at Eurofins, but has no idea what to do with the numbers that are shown on the report. Do you have a "simple" translator of the numbers that you show in your report to "how much fertilizer do you have to give of which product?" So how does this translate in m3 cow-muck that can be injected in the field and how many kilos of lime (to increase the pH) and which fertilizer to use in kilo per hectares.

The recommendations in kg N or kg lime are at page 2 and 3 on the report. So that would help for this.

 

What do you think about using horses feces on mushroom farms as a fertilizer in the Netherlands?

It is used a lot for the growth of mushrooms. Also the product after mushroom growth is used again to improve soil fertility.

 

When is it best to test horse pastures? How many samples are needed and how frequently?

Soil fertility assessment can be done every 4 years and the best moment is during winter period.

 

In the Netherlands we have a problem with iron toxicity of the ground water and soil on some locations. Could we influence the uptake of iron from the soil into the grass with manipulating of the fertilizer? With the goal to make these fields useful for harvesting? Or is harvesting no problem at all because the iron is mostly located in the sand?

The availability of iron (Fe) in soil is related to soil pH. A high pH results in a low availability of Fe, so I would suggest that there are no problems present. Low pH soils, it could be an issue and as such I would suggest to apply water instead of fertilizers, since the uptake of nutrients is in the top layer of soil. If the iron is in lower layers, uptake is not affected. A good idea would be to test the nutrient levels in the grass that is grown. Nutrient levels + target ranges gives you a good view on the Fe levels (and other nutrients)

 

How does availability reflect grass content as they are not always directly linked?

Weather conditions play an important role. This year we have a 'late' season in The Netherlands, due to low temperatures in the night. In combination with a lot of rainfall, grass production is very high (some grasslands > 6000 kg DM/ha already). As such, nutrient uptake is not always related to soil fertility.

 

When is the best time to have your soil analyzed to prepare fertilizer treatments for the pasture? How often should you have the soil analyzed?

Soil fertility assessment can be done every 4 years and the best moment is during winter period.

 

Can high water tables disrupt mineral availability to the plant and create more antagonistic effects between minerals such as elevated Molybdenum?

Lots of water dilutes the content in the uptake zone of a root. I don't think that high water is antagonistic or resulting in antagonistic effects (but I’m not sure).

 

So many horse owners are worried about adding nitrogen to pasture because they do not want rapid grass growth yet they do not realize the importance of P and K plus Sulphur. How can we promote good practice to owners for improving soil nutrient content for sustained grass growth?

We use a lot of monitor projects in which we show the results of the actions done (fertilizer application etc). To me, showing these results and discussing the possibilities with the owner and user of the land helps a lot.

 

Selenium has been added to fertilizers in Finland since 1984. Today the addition 15 mg/kg. Uptake by plants is not very efficient, but the total human Se intake has increased. Is there still a need for Se supplementation in equine diets?

Selenium is essential for humans and horses. But it has essentiality not been proven for plants, yet. In my opinion, it is difficult to prove the essentiality of Se in grasses, but grass is eager to take up Se form fertilizer. So it is a good supply (roughage) for Se.

 

After a wet winter, many horse paddocks will have a high level of moss, preventing grass re-growth in the spring. Other than physical disruption by harrowing, do you have any suggestions for minimizing moss proliferation?

The use of Nitrogen fertilization

 

Could we influence the uptake of iron from soil into the grass with manipulating fertilizers (to make high iron soils more available)?

The type of fertilizer is relevant here. Application with spraying of the fertilizer, or use the chelated form of the fertilizer. In a chelated form, the nutrients are protected and are efficiently used for uptake.

 

Selenium in soil not necessarily taken up by plants I understood - am I correct - this fits with your uncoupling comments?

Selenium is essential for humans and horses. But it has essentiality not been proven for plants, yet. In my opinion, it is difficult to prove the essentiality of Se in grasses, but grass is eager to take up Se form fertilizer. So it is a good supply (roughage) for Se.

 

For iron, the availability in soil is related to the pH of the soil?

Correct, and the type of fertilizer is relevant here. Application with spraying of the fertilizer, or use the chelated form of the fertilizer. In a chelated form, the nutrients are protected and are efficiently used for uptake.

 

A low pH results in a high availability of iron?

Correct, and the type of fertilizer is relevant here. Application with spraying of the fertilizer, or use the chelated form of the fertilizer. In a chelated form, the nutrients are protected and are efficiently used for uptake.

 

So increasing pH by lime is a good way to improve the soil and to reduce uptake of iron?

Correct, and the type of fertilizer is relevant here. Application with spraying of the fertilizer, or use the chelated form of the fertilizer. In a chelated form, the nutrients are protected and are efficiently used for uptake.

 

The amount of moss can be reduces by N-fertilization?

Correct, and the type of fertilizer is relevant here. Application with spraying of the fertilizer, or use the chelated form of the fertilizer. In a chelated form, the nutrients are protected and are efficiently used for uptake.