From what I have seen, the most fundamental difference between farming in the US and Ireland is not the crops grown or the scale of the farms, but the level of knowledge surrounding soils. The farmers and advisers that I met while in North Dakota had a huge amount of knowledge about their soils, in terms of how they were formed, the parent materials, mineral composition, water flows and all the associated soil science.

It struck me that this level of knowledge about soils doesn’t exist in Ireland, except by a small few. Maybe it’s because most Irish farmers grow grass and don’t till their soils each year so they don’t see the soil? Yet all Irish farmers grow crops, it’s just that grass is perennial – so the soil, and how we manage it, is critical if we expect to get high yields.

Average corn yields in the US have been increasing each year since 1940 when the use of nitrogen fertiliser became widespread. The rate of yield increase shifted a gear in the 1960s with the use of hybrid corn varieties and a further yield increase has been observed since plant genetic engineering started in the 1990s.

The point is that these yield increases wouldn’t occur if the soil wasn’t being managed correctly, as everything comes from the soil. All the plant breeding in the world is worthless if the soils can’t support the crops. With this in mind, Irish agriculture needs to take a reflective look at itself.

Nine out of 10 soil samples sent to labs in Ireland are deficient in essential nutrients for growth. About 50% of Irish farmed soils are considered heavy and require drainage.

The current generation of Irish farmers have largely undone the hard work started by their grandfathers in the post war era. These men spread twice as much lime and five times as much phosphorus as is currently being spread and initiated largescale drainage programs – most of which have now fallen into disrepair.

So why is North Dakota different? The local university, North Dakota State University (NDSU), has a large and well-funded soil science department, involved in teaching, research and extension. It appears that the trickle down of knowledge transfer in this region is working really well.

Drainage

While the land along the Red River valley in North Dakota is very fertile, drainage is an issue. The soils have up to 70% clay content, making them extremely heavy. This is reflected in its dark black colour and also its weight – a lump of soil weighed similar to a lump of concrete.

Rainfall in this part of the United States is low by Irish standards at 500mm per year, but spring floods are a problem when the snow melts.

Due to the flat nature of the land, getting water away is an issue. Even after just a couple millimetres of September rain, fields can become waterlogged.

It’s no surprise that a large part of the NDSU soils research budget is taken up on drainage projects. Lowering the water table through drainage opens up air pores in the soil, allowing for improved root growth and development, which gives a yield response.

There is another benefit to drainage in this part of North Dakota also and that is to do with salinity. The salt content of the soils is high and when the water table rises, it brings the salt crystals with it. Salinity is a big issue here because when salts rise to the surface, crops won’t grow and soils with a high salt content suffer from low yields. Drainage helps to alleviate the impact of salination by keeping the water table and the salt levels low.

How they drain

Andrew Fraase is a drainage consultant who works for Centrol, a large crop consultancy firm based in the Mid-West which is also a drainage contractor. Andrew works closely with the soils department at NDSU on some of their research projects. He graduated from NDSU with a masters degree in soil science and he now heads up the drainage team for Centrol.

I caught up with Andrew as he was draining an 80-acre field near Grand Forks in North Dakota. Half of the field was still in corn that wasn’t yet harvested, so Andrew could only work in the part of the field where wheat was harvested.

Before going into the drainage detail, I asked Andrew what are the first steps when undertaking a drainage project.

“The first step is to assess the site. I usually start at the outlet point. Sometimes, there is no obvious outlet or the outlet is too high with an insufficient fall. In these cases, we would need to investigate installing a pump, but this will add a bit to the cost.

“I’ll have maps of the field and also soil maps of the area and I’ll bring these with me when I visit the site. Based on the soil type and the amount of water to be removed, I’ll design a plan. The main decisions relate to the depth of the pipes, how far apart they are going to be, the dimensions and whether or not we need to use a filter over the pipe.”

In addition to the soil maps, Andrew can use a soil conductivity meter, which is a probe device that goes behind a tractor to create a map of the wet and dry parts of a field. Conductivity is higher in wet soils. This information will be used to alter the pipe spacings.

The standard model adopted by Andrew is to use tile drains at 12m to 20m spacings and about 0.9m to 1.5m deep. Due to the nature of the soil (high clay content with no naturally occurring rock), stone is not normally used in the drains. However, a special filter sock is often used around the pipe to help keep silt out. After devising the plan, Andrew loads it up on to the GPS software and orders the materials to be delivered on site before the team arrives.

When I visited the site, the team was installing the main line. This is the large pipe located at the lower end of the field which all the field drains are going to feed into. This was being mole-ploughed in by a massive 550hp self-propelled mole plough. This pipe is positioned about 25m back from the field boundary because Andrew doesn’t want roots from trees affecting the pipe.

The mainline covers a length of about 300m. About 150m of mainline closest to the outlet is 12in-diameter pipe, while the other half is 8in-diameter single-wall corrugated pipe. Andrew says that if he was doing more than 80 acres, he would use a twin-wall (smooth centre) pipe because of its better water flow.

Before the mole plough moves in, Andrew marks the location of the pipes by placing little flags in the ground. Blue flags mark where the mainline is going, while red flags mark the other lines. All the pipes come in rolls, even the 12in ones. A tractor with an attachment for handling the large rolls lays out the pipe in front of the mole plough and the flags indicate to the tractor driver where to roll out the pipe.

The mole plough itself is equipped with GPS, RTK technology and self-steer. GPS steers the mole plough along the planned route for the pipe, while RTK adjusts the depth of the mole while on the move. So as the mole plough travels over the natural gradients of the field, the RTK will adjust the depth of the mole to keep the slope of the tile drain constant.

The tiles that drained into the mainline were placed 20m apart and 1m deep. The mole plough can comfortably lay 20km of pipe per day. The cost of the job to the farmer was $800/acre (€711/acre). Andrew says that if the pipe was positioned closer and if a pump had to be installed, the cost would be closer to $1,300/acre (€1,160/acre). The researchers and farmers expect the investment to be paid back through higher yields within four to five years.

Comment

I fully accept that you can drain land, but you can’t change soil type.

However, effective drainage still makes a huge difference.

While the drainage practices I saw in the US were not directly applicable to Ireland, because of the different soil types, it was illuminating to see the system work.

If we are to fulfil our potential as a dairy producing country, we need to start managing our soils better.

We have a few good soil researchers, but not enough, and their knowledge isn’t trickling down to advisers and farmers the way it is in North Dakota.