Grass grows because it is nuclear powered.

Sunlight is the energy provider, with the greatest limiting factor to pasture growth in NZ pastures being lack of sunlight. This may be hard to believe at the end of, or during a severe drought, such as experienced over most of the country during the 2012 – 2013 season. On seasonal averages however, sunlight is the limiting factor. It may be argued that the sun's heat, is what recycles the water from the oceans as rainfall, so even the rain, is nuclear powered.

All living plants and creatures require a source of energy; other than nuclear power generators, all energy on earth comes or was generated by sun.

That is why in winter; grass on a northern slope will always grow faster than southern, if they are of the same fertility level, which of course is unlikely.

Annual grasses, with flat broad leaves, facing the sun in early spring, grow faster than perennials, which being more boat shaped, survive heat and dry. The Rye grass Droughtmaster is an example of adaptation and breeding for hot dry conditions. The thin V shape restricts sunlight, giving less evaporation and wilting, but less capacity (surface area) to absorb the suns energy when it is limited, winter / spring.

Pastoral farmers make a living, because we farm animals, ruminants, capable of harvesting plants that harvest the sun's energy. Animals cannot do this.

Ruminants are well equipped to eat plants we could not utilise, such as grasses, convert them into products we can use, and market.

The skill required of farmers is to maximise the ability of pastures to harvest sunlight in the form of carbohydrates and proteins, then to maximise utilisation by ruminants. To do so as efficiently as possible, while maintaining the sustainability of the system, providing a healthy environment for all animals and humans involved, and in so doing make a dollar, (or two) is, or should be, the aim of pastoral farming.

Air

Air is the source of Nitrogen (N), necessary for all plant growth. Oxygen from the air in the soil, allows aerobic bacteria to decompose recycle organic matter. Most beneficial soil organisms need oxygen.

Plants feed from soluble nutrients carried to the roots in soil solution.

So, they need air and water.

How is it possible to have both air and water in a soil at the same time?

Good soil structure promotes air and water in a plant friendly balance. Too much of either, results in no growth, poor recycling, leaching of nutrients faster than necessary.

Many books have been written on this subject,  but they all endeavour to inform as to what is good farm practise.

Very briefly, topics covered would include the soil biology i.e. the environment to maximise soil building, nutrient recycling earthworms, organic matter, avoiding of pugging and cultivation methods that breakdown organic matter (O.M.) or drive out air.

Most earthworms prefer pH over 5.6. However, different species have different tolerances and different functions. The dominant species will give an indication of the soil's potential productivity, and indicate where modification of the farm practise may improve productivity. All earthworms need feeding. 15 tonne dry matter (DM) should give 50% more worms than 10 tonne DM.

To get DM 15 tonne + pastures need nutrients to enable the harvesting of sunlight, such as N, P, K, S, Mg, Ca, Trace Elements.

Considered a soil amendment, rather than a nutrient, lime has an important part to play in ensuring soils are providing the ideal environment for pastures to grow.

Usually, raising pH is what is thought of when liming is considered; this is indeed a major contribution lime may make in optimising soil conditions for bacteria, fungi and the myriad other organisms that make up what should be 30 tonnes living creatures / ha soil, that all contribute to establishing and maintaining soil structure.

Lime has many other benefits, not the least being the Ca content improving flocculation (the granulation of soil particles, allowing the more free passage of roots, air and water).

Although clover makes a significant difference to an animal's nutrient intake compared to a grass only diet, clover has the ability to provide vital N for grasses. This has been the traditional method of growing grass in New Zealand. The fact that we have other sources of N to economically grow grass, in the form of N fertilisers, does not mean that clover should be discarded as an economic source of N for pastures. The cost of substituting clover N with fertiliser N should always include the substitution of animal nutrients that clover provides in greater quantities than grasses. For example, Ca in clover is 2 to 3 time higher than in ryegrass. Most of the products the farmer markets are high protein products, i.e. milk, meat, wool, hide; clovers contain a higher protein % than grasses. Some trace elements necessary for the utilisation of major elements, are higher in clovers, boron (B) being an example.

Air in the soil is used by bacteria on clover roots which in a high energy requiring process, take the N and O and recombine these two elements to fix Nitrate, another vital reason for good soil structure.

This high energy process requires an adequate supply of phosphorous (P), plus other major and trace elements. This means, if the clover is low in P, it will be low in everything else. Lacking P and the ability to harvest the sun's energy, it will have a poor rooting system, be unable to extract nutrients that may be available to a more vigorous plant, resulting in poor N fixing, lack of feed and poor nutritional quality for ruminants.