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Pasture Development Science
Why not High Dairy Production?
Why does Northland have historically lower production figures, particularly in our Dairy industry, compared to some other higher producing areas?
In a sentence; because those areas have free draining and more consistent soils, in a word; drainage.
Poor pasture growth and lower than optimum production occurs when soil lies wet, or is saturated even for a few months of the year. Fertility is reduced, up to 60% of phosphate is locked up (on wet slopes up to 90% of Autumn applied fertiliser is just washed away into streams, researched fact), undesirable grass and weed species enter the pasture, taking nutrients and crowding productive grasses. Worms do not thrive and oxygen is excluded. This not a recipe for pasture development. In fact severe weather events have been calculated by formula to show economic loss of pasture growth by the quantity of rain in the event, even on reasonably good un- drained land.
Where does the science come from?
In the 1980's Massey University ran a farm on which much subsurface drainage research was carried out, and also hosted the New Zealand Drainage Association, which eventually ceased to function with the advent of funding cuts and the internet. Much research had also been done in Britain, Canada, and the U.S. Several key authors also produced manuals covering world wide science in subsurface drainage.
Consequently, we have researched knowledge, and our own discoveries and developed techniques over 29 years of practical drainage installation, and 10 years of cleaning and rejuvenating drainage systems and finding out what went wrong.
When using a design engineer, drainage is designed to a 'Drainage Co-efficient', which is 'the amount of excess water above field capacity that is removed per Ha. in 24 hours'.
We try to design all our plans to 25 mm extraction per day, which is the most economical drainage co-efficient to maintain a controlled water table, and the best option for control of rain events that would cause economical loss of pasture growth. Those that exceed this are of course minimised.
So what makes it work?
When wetness and high water tables exist, the rooting system of plants becomes stunted, and exist in the average dry zone in the soil profile. In the winter they have insufficient soil and nutrients, and in summer the roots are too shallow to find moisture so dry off rapidly.
For optimum pasture growth (crop and horticulture), certain environmental requirements are necessary apart from nutritional factors.
1. A depth of soil profile with a constant water table that allows the plant to develop maximum healthy root growth potential.
2. An Oxygenated environment that supports worms and soil microbes, and allows nutrient conversion and uptake from fertilisers.
3. Rapid removal of excess water over field capacity to protect deep root development and to prevent pressing and pugging, in turn preventing pasture loss from trampling and compaction.
Subsurface Drainage achieves all this with water table control.
So here is the big secret.
When the water table is controlled or constant to a depth of 0.5m to 0.8m, or deeper, you are farming 60% more soil than un-drained land.
And plant species will use it all. No wonder that the grass grows!
That is the same as buying more land, which makes drainage highly affordable in the planning of the progressive farmer.
So What does it cost?
Costs vary from job to job. Flat land with outlets into an open drain are the most cost effective. Then there are systems where several hundred metres of pipe may exit one outlet via a mainline. Then again there are sloping land systems trenched at depths of 1.6 metres, which may have multiple outlets or one for a 1000 m system. There are several pipe sizes and types which we utilise to keep minimum water flows in the pipes to minimise silting and changes to critical water flows. Drainage aggregate use (metal) also varies job to job. Pipe clay is surcharged for wear.
So pricing is complex, yet strangely similar by average. Generally speaking, as at 2015 summer season, costs vary from around $21 to $25m. Flat land metres per Ha is around 250m, so you could say average costs are around $5625 per Ha. plus GST Contact us for a closer estimate.
What are the results?
Here is an actual Northland research table 1993 to 1999. Left in the prices of the day for a bit of history. Note the trend in carrying capacity, individual cow and per Ha trends. These production gains are set in indefinitely, and only get better as the soil matures.
season cows milk per per production value at Drainage cost at interest @ comments
solids Ha. cow gain kgs $3.30 kg nom. $8 perm nom. 11%
93/94 336 93,991 626 270 3,165 $10,444 $41,600 $4,576 1st installation
94/95 340 97,156 647 285 4,009 $13,229 $3,427 No installation
95/96 341 98,000 653 287 17,223 $56,836 $32,584 $5,554 2nd Installation
96/97 350 111,214 741 317 5,277 $17,414 $23,992 $1,941 3rd installation
97/98 331 99,268 661 300 10,009 $62,729 $29,408 $3,260 Drought year
98/99 370 *113,000 ______ _______ _______ _______ Project in credit
*Conservative estimate Av Gain 96/97 = 18% 48,683 $160,652 $127,584 $18,754
97/98 = 5.6% $146,342 credit
98/99 = 20% $14,310
Footnote: This happy farmer continued with more drainage in 2000 and 2001, and now enjoys approx 25,000 kg more production per average season. Work this out yourself at today's payout price. This farm has produced 350,000 kg,s over the last 14 years, for free, as against the undrained state of the farm before drainage. Subsurface Drainage is a long term profit making tool for the progressive farmer.