What, I believe, has been overlooked in the Murray Darling irrigation area discussions are the importance of healthy soils. If we can put somewhere between 10 to 15 percent of water back to the environment without affecting the productivity of the irrigation area, what a result that would be for our food bowl, rural Australia, and every Australian.
In 1979 I started a fertilizer spreading business, and 20 years later we were the largest spreading contractors in the state of NSW. The areas that I’m familiar with are the Macquarie, Lachlan, Murrumbidgee, and Murray river systems. The reason for our rapid expansion was innovation. We made purpose built conveyors to add 8% moisture to the lime. This eliminated the dust problem, stopped the fine lime from blowing away and allowed us to spread a wider pattern.
After much trial and error and reversing the spinner, we built unique spinners and frames for spreading the moist lime. This eliminated the dust problem, stopped the fine lime from blowing away and allowed us to cover a wider pattern. Although lime is essential to the soil, we will focus on the calcium magnesium percentages in our soils and the setting up of genuinely independent agronomy trials.
I first became aware of the water efficiencies when we limited half of Chris Taylor’s central pivot irrigation on his property south of Dubbo. The pivot at the time was the third largest in Australia and was on a consistent soil type; we limed half the area of the pivot. When we returned the following year to lime the other half of the pivot, Chris informed me that the corn on the limed section had a ten percent increase in yield, everything else had remained the same. I knew then there were a lot of soils that would show a more significant rise as Chris’s soils were of high standard.
For those who a not familiar with soil science, magnesium controls photosynthesis and in high percentages makes the soil tighter. Calcium causes structure improves water infiltration and leaves the soil in a more friable condition. The easy way to remember this is by knowing that the opposite applies to the human body which is why magnesium tablets are taken for cramps and calcium makes your muscles tighter.
Our soils types in Australia are among the oldest in the world. We have a considerable variation of soil types from the Great Dividing Range where there is a calcium/magnesium deficiency to the predominantly high magnesium low calcium soils of the irrigation areas in the Murray Darling. The soil in the irrigation areas often has an artificially high PH because there are high magnesium, potassium and sodium levels. Magnesium has about 1.5 times the neutralizing value than that of the calcium. The good books state you cannot lime a high PH soil because you make nutrients and trace elements unavailable.
I started to question this information because of the results we were getting. The dump sites where the lime was tipped, if you clean them up properly the concentration of lime on the ground would be ten to twenty times of what was spread on the field. The crop on the dumpsites sometimes was better than on the rest of the area.
This is where the controversy starts!
When you lime these soils, you displace the magnesium, potassium, and sodium which have a higher neutralizing value. There is a pie chart which is used in agronomy. If you put say calcium into the pie chart, you will have to take something out. In this case, calcium and magnesium have two positives. You push magnesium and if in excess you will take out potassium and sodium.
This is how we have managed to keep the PH in check, and because the soils usually have a heavy exchange capacity, this also helps to keep the PH in check. The heavier soils require a more substantial rate to correct the imbalance, and the lighter soils need a lighter rate to correct the imbalance.
In balance, the fertilizer efficiencies improve one unit of nitrogen will grow one bushel of corn when out of balance it takes one and a half units of nitrogen to produce a bushel of corn.
Drip irrigation has a significant role to play in the irrigation areas and having the correct calcium/magnesium balance improves the ability of water to disperse through the soil profile. Biological farming may well have a significant role to play; they are also heavily dependent on calcium.
The cost of genuinely independent agronomy trials through the Murray Darling that will show the correct balance on how to gain greater water efficiencies. I estimate would be a cost of around six million dollars and with the productivity increase created a return on investment in five year period. If someone can improve on what we have achieved with the help of many others, I would welcome this. The Murray Darling is crucial for the growing of food and fiber for our nation.