There are several things that caught my eye while scanning through a Beef and Lamb Lucerne blog. Chemicals, insects, weeds, and fertiliser are among them. The Americans use Alfalfa to mop up nutrient excesses. We seem to use Lucerne to create deficiencies. The American excesses are a result of feed lot manure from 50,000 or whatever number of cattle being spread on relatively small areas of land. They then plant Alfalfa and cut that for forage for the cattle for a few years, then perhaps lease the area out to a vegetable grower for a while before the cycle starts again. They are not legally allowed to use the manured areas for at least two years to produce food for human consumption because of Salmonella concerns. 

Lucerne is a gross-feeder. It is a very hungry crop. If you want it to out-last and out-compete weeds, then feed it. If you want to produce 20t/haDM and more, then that crop will remove approx. 500kg N, 440 K, 275 Ca, 56 P, 56 Mg, 56 S, and 1.2 Mn, 1 Cu 0.8 B 0.4, Fe 0.4, Zn 0.3, and Mo 0.02. These figures may vary, but what matters is, the crop will take all you throw at it, and in 90% of cases, more. Let’s work through the list. Nitrogen, 70% from the air is 350 kg; then 100 kg from the soil is 450 kg, leaving 50 Kg to be applied from the bag. That 70% from the air is not by necessarily correct either.  You’ve got to earn that right. That is achieved by ensuring you have: (1) adequate calcium and magnesium in the correct amounts. This requirement is calculated for each soil. (2) Available phosphate, at least 560kg/ha. (3) Available iron, at least 200ppm, but be aware, iron may be found at depths beyond the soil probe. (4) Cobalt at about 1ppm and (5) Mo at about 1ppm. 

Potassium is perhaps the nutrient we have found to be the most deficient; about 50% in most cases. Not only that, but most people use potassium chloride because it is the cheapest form of potassium. Bollocks! Use potassium sulphate instead. For a start, you won’t get those aphids we keep reading about. I've seen them on neighbouring crops too, but they are only a temporary on our crops, at the beginning of when a grower converts to our programme. You won’t have to spray toxic chemicals. You’ll grow a better crop. Besides that, there are many reasons to change and they all point to greater profit in your pocket.  

• More Energy. Potassium Sulphate costs more per unit, but delivers better value. Money spent on potassium sulphate will purchase less fertiliser by weight than will dollars spent on potassium chloride; but the dollars spent on sulphate will buy significantly more crop growth energy. 47% of potassium chloride is chloride and of little use for crop growth. The more chloride plants have, the less anions they will have, including sulphate and nitrate. In contrast almost 100% of potassium sulphate is useable by the plant.

• Lower Salt Index. Potassium sulphate has a salt index of 46. Potassium chloride is 116. The higher the index, the greater the chance of damaging germinating seeds, seedlings and soil biology.

• Better Uptake of Potassium. Uptake of potassium requires it to be in the phosphate of potassium form. When there is an excess of chlorides the bonding of potassium with phosphate is blocked. The end result is less potassium uptake into the plant in the preferred form. The sulphate form does not overwhelm the soil solution with chloride ions and consequently more potassium is taken up by the plant.

• Microbial Stimulation vs. Microbial Suppression. Sulphates have a stimulating effect on the microbial system in the soil whereas chlorides at high levels are very hard on soil biology and are seldom recommended by creditable sources. A small amount of chloride is actually beneficial for soil microbes. This modest requirement is easily met by the 1-2% of chloride in potassium sulphate.

• High rates of chlorides can destroy soil carbons. Humus destruction leads to greater nitrogen leaching as soil nitrogen levels are dependent on humus levels. The better the humus percent, the more anions (particularly nitrate, sulphur and boron), are held in the soil, and the better the moisture retention. Potassium chloride is the product above any others that makes your soil as hard as concrete in summer.

• Plants and soils need sulphur. Most NZ soils are sulphur deficient. In order for plants to make oils and sulphur bearing amino acids such as cysteine and methionine the plants need an adequate supply of sulphur in the sulphate form. This is exactly what potassium sulphate supplies.

• Better palatability. Pastures, crops, vegetables and fruit taste poorly when the potassium comes from potassium chloride (that’s right, even stock prefer fodder grown with potassium sulphate). This happens because chlorides are also taken up by the plants. Fruit and vegetables grown with calcium chloride taste bitter; this is the main reason why children reject vegetables.

• Less is more. The application of 100kg of sulphate will usually give a greater plant response than 200kg of chloride. This relates to a soil where the cations are balanced and soil potassium is adequate.

• Potassium translates into quality and quantity. The life of your stand depends on it. Potassium is vital for quality and yield. It hastens recovery after harvest, and ensures long-life of a stand. Leaf-drop and spotting are eliminated. It also improves leaf to stem ratio, winter hardiness, and nitrogen-fixing.

• Calcium. How many of you add calcium to change pH? How about adding calcium because the soil and the plants need calcium? Calcium, along with boron carries other nutrients into the plant. Leaf test prior, then apply calcium alone, test again and see the difference in levels of all nutrients. Each soil has its own sweet spot as far as calcium (and magnesium) is concerned. That can only be established after soil testing and mathematically calculating it.

• Phosphorus is required between 336 and 560kg/ha in the soil, (sometimes higher) depending on how light or heavy it is, but mostly around the 560 level. I have seen many soil tests where it is about 1,000 or 1,500 and more, (even 3,000) and still the farmer is too scared not to apply more. What a waste of money, quality and potential.

• Magnesium. How many of you apply lime without magnesium? Each time you do that, the magnesium percent of the base saturation is driven down roughly on a 1 to 1 basis, provided it is high enough in the first place, which it rarely is. Many soils get over-limed too, making matters worse. Lack of magnesium (or too much calcium) can cause yellowing in Lucerne foliage. However, deficient nitrogen, sulphur, manganese, and iron can also have a yellowing effect, making a correct diagnosis difficult. As for calcium, the correct level of magnesium can only be established from a soil test.

• Sulphur increases the girth of plants. It is required with nitrogen to form amino acids which in turn form protein. Too often it is left out, or too little is added to the fertiliser. It leaches because we are collectively converting soil carbon into atmospheric carbon. The higher the organic matter, the more sulphur you can attach to humus in the soil. Sulphur also influences flavour (palatability). It would be alongside potassium as the most deficient nutrient found.

• Manganese needs to be 50-250 ppm in the soil. It’s involved with seed formation & can improve germination and survival of seeds for those growing seed crops.

• Copper is needed from 2 ppm to 15 ppm. The higher side is better. It improves plant and stock health benefits and confers elasticity in plants, so they will stand up better, reducing lodging. Fruit growers do not appreciate branches breaking when loaded with fruit. Correct copper, potassium and manganese can prevent that from happening.

• Boron is hugely important, partnering calcium and silicon. Without boron, the plant cannot transfer sugars from leaves to the roots. Boron is required at at least 1.75ppm in the soil. Boron toxicity is not usually a problem when the calcium level is correct.

• Iron needs to be at least 200ppm, but always at least 5ppm ahead of manganese. There are plenty of soils out there the other way around. You really don’t want to be in that category. The manganese will oxidize the iron in the leaf in that situation. Iron can be found beneath the depth of a soil test probe, so do not apply iron before ascertaining that the situation requires it.

• Zinc partners phosphorus. If phosphorus is high, zinc needs to be 19.5 ppm in the soil. If phosphorus is very low, zinc at 6 ppm is adequate. There are many cases of high phosphorus but low zinc all over the country. In those cases, water efficiency will suffer. If zinc is high & phosphorus is low, the phosphorus will be blocked. When it is the other way around, zinc uptake by plants will be blocked. Either way, water efficiency of the plant suffers. Soil zinc levels appear to be increasing as facial eczema control continues. 

• Molybdenum needs to be at 1ppm in the soil. There are dozens of soil tests where it is around 6-8 ppm. If that is the case, get the copper up. I have only recommended molybdenum to be applied to one crop I have tested. That was citrus and the grower pointed out the visible symptoms that were later confirmed by the PAL soil test. The molybdenum level was 0.95ppm, but those deficiency symptoms were quite visible.