Digging deep into an
A paddock of two halves. This view looks down down the northern, better half. The poorer-performing area is at the back, to the right. The other half. In both pictures the dry stalks are remains of parsley dropwort flowers, which needed to be mown off. When the cows first come into this paddock they do seem to prefer the better half, although that may be because of quantity of feed available, as much as quality or type.
of good production if managed well.
But it is easy to see a changing gradient of ‘goodness' across these flats, from paddocks which grow grass very well to areas obviously much less fertile. That fertility seems related to its height above and distance from the largest stream, although that may be coincidental.
Complicating that observation is that some of the struggling areas were used for potato cropping for a few years, which disrupted the soil profile and presumably depleted some nutrients.
There are a few paddocks where the differences are very noticeable. Parts of those paddocks grow an excellent, dense sward of the changing seasonal grasses I expect to be there, but in other areas there is a much reduced variation in pasture species and far less
growth in the plants. There is usually also a greater number of various weeds.
I've tried to address what I assumed was going on in the poorer areas, putting on heavier dressings of lime and fertiliser in those places. They have gradually improved to some extent, but progress has been slow.
On a small property one tends to do a soil test on an ‘average' area that generally represents the landscape, and then extrapolate from that for fertiliser application. Some areas have responded very well to the chosen treatments, but not universally achieved my desired aim.
I realised if I was going to get a better understanding I would have to dig a little deeper and find out what was going on and how best I might address the problems. I decided to 'do some science'
on the most
In very dry conditions ground cover becomes sparse in this area. Where kikuyu is present, the ground remains thickly covered even in the middle of a drought.
varied paddock to see if I could identify the problem. Half of that paddock is alright and most of the other half is poor. The 'average' approach to fertiliser in that area hasn't worked well enough, so it was time to find out what it specifically needs.
I spoke to my most regular soil fertility consultant, from whom I haven't actually bought much product, but Steve Polglase from Agrifert is the most interested and interesting consultant I've had contact with. He came up late one afternoon and the two of us walked around the paddock, examining the pasture composition and taking soil plugs for later testing. I suggested that I wanted to take three lots of samples, in three strips, down each side of this paddock and (with permission) one lot from the neighbouring property as well, which was once part of the same paddock but has had no fertiliser nor lime for nearly 30 years. I thought the three tests might provide some useful comparative information. Steve was initially doubtful but as we walked around he agreed there were quite obvious differences between one side of the paddock and the other.
In the first strip the grass is dominated by kikuyu, growing well, with quite a bit of white clover amongst it, along with
some rye and paspalum (since it was still late summer), a bit of left-over parsley dropwort, some self-heal and so on, all nice stuff for cows to eat.
On the other side of the paddock the pasture has generally been quite poor. Even the kikuyu doesn't grow well there, or even at all in some places. I've long been suspicious that it was the fertility of the soil to blame, although Steve and I discussed the possibility that soil type could also be playing a part.
Many people think kikuyu is a dreadful pasture grass, but it grows well in our climate so if it isn't in a particular location, I want to find out why. Summer 2014-2015 was quite dry early on, but we had good amounts of rain in autumn and such conditions are exactly those to make kikuyu grow well. In my experience, if it doesn't there's something pretty wrong underneath it.
The predominant species on this poor side of the paddock is Axonopus fissifolius or narrow-leaved carpet grass, with its cute little seed-head which looks a bit like a bird's foot with two toes and a lower ‘thumb'. It's a grass the cattle quite like eating (and I remember liking it in my lawn because it was easy to cut with a hand-mower), but its nutritive value is The roots of the
grasses in the poorer area were deeper than we expected to see and there were
earthworms, despite the dry
conditions. apparently not high. It has always been an indicator of lower fertility, or lower ph in our pastures, particularly where it has become the primary species in an area. It also grows in the higher-fertility areas quite well, but presumably ends up where the other plants can't compete as strongly. It's also possible there are fertility or acidity issues in those spots too.
Over the fence in the neighbour's place things were far worse, with only very small bits of kikuyu growing weakly in some places. The dominant species was the carpet grass, with a bit of paspalum thrown in. While well-fertilised areas of our place were currently growing a lot of kikuyu and clover quite quickly, this pasture was puny and dry-looking.
Back on my side of the boundary, Steve dug up a spade-width of soil in the good and poor areas of the paddock for us to look at the composition of the topsoil. He pointed out, among other things: • an orange strip of iron oxidation which indicates wetness, not surprising where 1900mm of rain falls each year and the soils are wet for several months over winter and spring; • that the plants' roots were toughly resistant to stretching, which he said indicates a lack of absorption of calcium; • that the roots of the plants in the poor area were, surprisingly, deeper into the soil than those in the good part of the paddock, although that may have been a function of the plant species since kikuyu tends to run across the top of the soil to a large extent; • a fair number of earthworms, a good sign considering the time of year.
Steve went on his way with my soil and pasture samples and we'll talk again before I write next month's column. I hope the soil test results will show sufficient differences to explain our observations.
There seems to have been a rising level of interest amongst farmers in the last couple