What crop do we grow?

Press, Volume CXII, Issue 33052, 20 October 1972, Page 10

What crop do we grow?

What crop do we grow? That is easy—grow the one that is most profitable. But we cannot grow all one crop, as we would have weed and soil fertility problems. Then grow as much as possible of the most profitable crop and then as much as possible of the next most profitable, and so on down the list until you have used up all the land. Ah; but that is still too simple. We have got problems with tractor hours and labour hours and grass for stock and putting crops in at the right time and making sure that when one crop is finished there is another one due to be sown so the land does not lie idle. Well then, how do we solve it? First we must decide just which is the most profitable crop. Sometimes it is easy. On most farms wheat is the most profitable and reliable crop. Then of course, we run into variety problems. The price for Arawa wheat is $1.35 and Hilgendorf wheat is SI.BO. Arawa yields better than Hilgendorf and it is usually more reliable. But if you get a good Hilgendorf year it will pay much better than Arawa. However, on most farms, Arawa will probably pay better than Hilgendorf, if you can sell it. So our decision must be a gamble. On most farms it is probably better to spread the risk. So we grow as much wheat as we think the soil will stand without overcropping. Wheat uses the paddock for about 11 months. Barley only needs about seven months. This means you can grow a crop of winter feed, then sow barley in the spring, and thus get two crops in one year. This can be just as profitable as wheat.

It is all rather complicated, especially when we throw in about three

varieties of peas, grass seed, and clover. There is also linseed, lucerne for processing. and various brassica seed crops. If we can grow 50 bushels of Arawa we need 36 bushels of Hilgendorf, or (at $1.50 dressed) 65 bushels of peas, or (at 85c) 90 bushels of barley to get the same net return per acre. In this way we can rank crops in order of profitability. Then we can decide which to grow, taking account of all the other ifs and buts, like soil fertility, not trying to do all the cultivation in one week in the middle of lambing, and making sure we do not leave too much ground idle for too long. There is a computer programme for working this problem out called linear programming. This can take into account all sorts of restrictions, including farmer preferences, keeping the work load to a reasonable level and so forth. It uses the same basic method that we have been looking at but does it very much more carefully and can examine far more crop combinations without getting tied up in knots by a mass of data. It will show the most profitable combination of crops and how many acres of each should be grown. It takes account of any re-

strictions we tell it to and also allows for the length of time different crops are in the ground. If the possible cropping alternatives are complicated enough it will usually work out a better answer than a fanner can do. For normal rotations, where there are a limited number of alternatives, you can probably work out as good an answer as the computer. Most farmers do not work to a set rotation. They have more or less the same acreage of each crop each year and try to avoid “hammering” a paddock by over-cropping it. This sort of approach works reasonably well but it is likely to lead to some inefficiencies. Some crops leave the ground in a much more easily worked condition than do others. If a rotation is arranged so that when there is a short gap between crops the ground is easily worked, and when the ground is hard to work the gap is longer so that the weather does some of the work, tractor hours will be saved. So deciding which crop to grow is a complex business. Growing as much as possible of the most profitable crop, then moving down to the next most profitable and so on is the best way to start. Making allowance for soil fertility and w’eeds is very important. as are questions such as not having land idle for too long and spreading the risk. It is impossible to say that this or that crop or rotation is best but. on an individual farm, it is possible to design a rotation which produces the most satisfactory results.

In the accompanying item H. Evans, farm advisory officer (economics) of rhe Department of Agriculture. Ashburton, seeks to help farmers in deciding what crops they should grow.