A New Zealand farm producing wheat and barley on the Waimea Plains, was experiencing very different growth and harvest rates in wheat fields where the same management processes were undertaken. The farmer was unsure of the reason(s) and determined to find out why. With the assistance of the Topoclimate South Pedologists he attained a good understanding of his soils’ structural characteristics and behaviour, and his profits increased.
The Topoclimate South Soil Survey Team came across this farmer while undertaking an intensive soil survey of the Waimea plains. As soon as the soil survey staff introduced themselves, the farmer asked “could you come out and look at this problem for me?” He then took the survey crew out to one of his wheat paddocks and showed them two different parts of the paddock.
The farmer had sown the crop on the same day across the whole paddock. In some areas the crop was only up to the survey staff member’s ankles while in other parts of the paddock the crop reached above his knees.
The survey staff could not believe how different the crop looked in the different areas of the paddock and suspected that the soil type and soil structure had caused the wheat crop to grow at two distinct different rates.
When they dug holes in each area and mapped the soils, they found that two distinctly different (but normally highly productive) soils were involved – Waikoikoi Soils and Kaweka Soils. The Kaweka Soil (on the right) was clearly better drained than the Waikoikoi Soil(left) and this was affecting crop growth.
After twenty years of continuous cropping, the well structured Kaweka Soil had maintained its structural character with sufficient pore holes to allow good drainage during wet periods, while the Waikoikoi Soil has started to structurally collapse from the regular cultivation by machinery and less soil pores meant impeded drainage of this soil slowing down the growth of the wheat crop.
After the staff had mapped the soils across the property and measured crop production from the two different soils, they reported to the farmer that the Kaweka Soils were giving him 10 tonnes of wheat per hectare while the Waikoikoi Soils were only producing 4 tonnes of wheat per hectare (which was less than the costs of production). They advised the farmer that he would be better off just growing his wheat crop on the better soil type and putting the areas of Waikoikoi soils back under permanent pasture to allow for the recovery of his soil structure. The farmer followed their advice and is now making more profit from just cropping wheat and barley on his Kaweka Soil areas and fattening lambs on the permanent pastures on the Waikoikoi soils.
When the discussion turned to how to manage the different land uses, the farmer pointed out to the Topoclimate South Staff that while it was easy to manage a paddock like 1 (on the map) where the whole paddock was mapped as one soil type (Crookston in this case), it was more difficult to manage a paddock like 2 on the map.
“The soil boundary in paddock 2 almost bissects the paddock. So what do I do here?” said the farmer.” Do I manage it for the better structured soil and continue to crop the paddock or do I manage it for the more poorly structured soil and return the area to pasture?”
Our suggestion to the farmer was to move his fences. By moving the left hand fence to along the soil boundary it would not cost him much in terms of materials and would mainly require his own labour, and would ensure that he can continue to manage the paddocks according to the soil structural characteristics of each soil type.
Fencing to soil boundaries, once they are identified accurately on a farm scale soil map is a useful tool for improving the productivity of your farm by ensuring that each paddock is managed according to its unique mix of physical characteristics.
The Topoclimate South Pedologists made some more tests on the two soil types to try better understand the differences between the two soils after twenty years of continuous cropping. Firstly they sieved the soil from both soil pits using a 12mm soil sieve and found some significant differences in the fine fraction and in the larger soil particles.
The Waikoikoi Soil had a much higher proportion of solid clods and less of a fine fraction, due to soil structural collapse under the continuous cropping regime.
The other research project that the Topoclimate South Pedologists were able to carry out to assist this farmer, was to compare the structure of the two soils under two different management regimes (continuous cropping and long-term pasture). When soil pit profiles were observed for each soil type, the Kaweku Soil showed very little differences in structure; drainage characteristics or soil layers.
In contrast there were noticeable differences in soil structure, soil drainage and soil layers in the Waikoikoi Soil after twenty years of continuous cropping compared with the soil profile under long-term pasture. The Waikoikoi Soil had a much higher proportion of solid clods and less of a fine fraction, due to soil structural collapse under the continuous cropping regime.
A good understanding of your soil structural characteristics and behaviour is essential to making better farm management decisions. Refer to the articles;
Why maintain good Soil Structure? and
The Why and How of Defining your soil’s texture for more information.
