Rotations are key to success

July 19, 2017

Crop rotations have the potential to increase the amount of home-grown forage harvested and hence lower the cost of feed.

As a general statement, few would dispute home-grown feeds are cheapest.

However, we need to look at this more closely. Should we talk just feeds per se, or energy?

It is energy we convert to milk. We should be discussing the cost of energy in any given feed when deciding what is cheapest. Effectively, feed dollars converted to milk dollars because this is the real determinant of profit.

Home-grown forage may or may not be the cheapest forage, but grain generally stands alone on energy cost.

Home-grown forage cost depends heavily on the value of the land on which it is grown, the yield per annum per hectare, its digestibility and energy density.

For our regular monthly clients we can determine grass grazed in tonnes of dry matter (tDM) and collate monthly averages for the full year.

We can add to this quite accurately tDM silage, measure summer crops and cost each out. Due to wide variations between farms on the above criteria, we choose to take a mean value for grazed pasture at $250/tDM.

This gives us a basis for silage cost, and good comparative data within farms from year to year.

Solid silage reserves can insulate us significantly from the many vagaries of season, grain and milk price we are subject to these days. Achieving these silage reserves also comes under our summer cropping program with crops such as sorghum.

Over many years we have come to realise some of the limitations to home-grown forage production. Things like compaction, pasture plants pulled up by grazing cows due to shallow rooting, declining plant densities, and falling yields which are now known to be associated with a lack of rotational crops.

Differing plant species remove and deposit different things in soil, but all contribute to improved yields. There are synergies to yield through plant rotations.

To resolve these impediments to yield we developed a Seven Year Paddock Plan for each of our clients.

The goal is to address the above limitations, improve soil health/organic matter and yield capacity. The basic idea is two years in crops, up to three crops per year, then back to pasture for five years.

We believe, based on overseas data, that we can increase home-grown forage harvested and hence lower the cost of feed, or rather, the cost of energy harvested/ha, through crop rotations.

This principle has been known and practised, especially by cereal growers, for many years.

Our potential to achieve this in our dairying areas is massive.

We have clients who have achieved dramatically increased tDM harvested over their farms simply through summer fodder crop programs.

We are now taking that to a new level with a more holistic plan spanning seven years. Our goals include improving soil health/productivity through rotational crops, addressing soil compaction, initially mechanically, but further through selecting deep-rooted crops.

Deep ripping has questions over its effectiveness in the longer term, and its possible damage to soil structure, but can certainly open ground to facilitate deeper rooting of crops/plants immediately following.

Rotational cropping has added potential to increase soil organic matter, an issue we think has deteriorated our dairy land’s productivity during the past 50 years.

The benefits of increased organic matter on an organic farm we work with showcase this potential. This organic farm nowadays would out-yield many conventional farms and has a per cow milk production average 60 per cent higher than the national average.

Crop root systems deposit organic matter in soils, as does stubble from crops, although nitrogen must be available to break down residue or new seedlings will suffer retarded growth until plant residue has been broken down.

A clover crop through winter can provide excellent high-calcium silage for dry and springing cows, but also increase soil nitrogen for the following summer crop.

Overseas research has demonstrated reduced weed and pest problems through rotational crop programs.

Calcium is essential for mineral movement in soils, making them available to plants, and for the same reason in cows’ digestive systems. The application of lime to farms has deteriorated dramatically over my lifetime. I suspect this too has reduced our soil’s capacity to support vibrant plant growth, apart from soil pH.

— John Lyne is a dairy production specialist with Dairytech Nutrition

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