Teagasc’s David Wall gave some advice on soil fertility at this year’s Teagasc national tillage conference.

As farmers look to reduce fertiliser use and look for alternatives to artificial fertiliser, David placed some fertiliser replacement values on organic manures and estimated their value.

He broke down the nutrient contents of 1,000 gallons of cattle and pig slurry and 1t of farmyard manure, broiler litter and spent mushroom compost.

These application rates would equate to the same as a 50kg bag of chemical fertiliser and the values can be seen in Table 1.

Farmers looking to build P and K indices while also adding nitrogen to the mix might look to broiler litter or pig slurry, while cattle slurry may be good value for maintenance of indices as well as supplying K for cereal crops.

While the table places fertiliser values on these products, it’s always important to consider the positive impacts these products can have on building soil organic matter and helping to improve soil structure.

Soil pH

David had some advice for farmers to make simple changes to improve efficiencies.

Correcting soil pH is an obvious one with 1t of lime available and spread for €22/t to 24/t in many areas. This will help to build P and K on low indices and help to maintain P and K indices where farmers are considering reducing rates on high indices.

Correcting soil pH can make nutrients more available and contribute to increased yield and return from crops.

Phosphorus

David demonstrated the benefit of having soils at index 3 for P and K.

He showed how a spring barley crop at index 3 receiving no artificial P fertiliser could achieve a yield of 8t/ha, while a crop at index 2 which receives no fertiliser may hit just over 7.5t/ha and lose out on over €100/ha in grain returns.

A crop in index 1 receiving no P fertiliser would see grain income decline by €411/ha.

While looking at P, he noted that Teagasc trials with three years’ work at seven sites showed a 4% to 5% increase in yield, where P was combined drilled with the seed compared to surface broadcast or incorporation into the seedbed.