Expert opinion

Ripping deep and planting wide

Last month we reported on the results from planting maize in narrow rows in Bergville. Now we go 250 miles further north-west for a completely different story.

Danie Minnaar, a commercial farmer and leading member of the South African Sandy Soil Development Committee (SDC) says that extensive trials have shown that in sandy soils, deep ripping has improved yields, by a consistent 2 tons/ha.

Mr Minnaar and his colleagues in the SDC are convinced that the no-till method of cultivation, so popular in other regions, is not a viable proposition for the sandy lands of the Western Free State and Northern Provinces. This is the area where most of the white maize is grown in South Africa. He points out that the sandy soils compact naturally and have to be managed accordingly. Extremely high temperatures in the region tend to negate the benefits of crop residues by effectively burning them off. The soils in this area have a clay content of only 4 – 8%.

John Deere 9570 RX 4-Track with Radium 5-row Triple-tine ripper. - Photos: Danie Minnaar
John Deere 9570 RX 4-Track with Radium 5-row Triple-tine ripper. - Photos: Danie Minnaar

Without ripping, the sandy soils can form a compacted layer that is as hard as concrete. The Minnaar farm has rainfall statistics going back 112 years and these show an average of 570mm per annum. Yields vary with the rainfall and also with the timing of the rain. The past 2 seasons have had good rains in February and March and this has resulted in excellent yields of more than 6.5 tons/ha.

Maize at 1.5m

On this farm, in the Kroonstad district, maize is planted at a row width of 1.5m. The cultivation practice is to deep rip on the row with 5 rows of tines spaced at 1.5m. On the latest ripper designed for this job, each row consists of 3 tines working at different depth. At the rear is the longest tine, with a chisel point, which can go in as deep as 900mm. Ahead of this are 2 more tines working at 600mm and 300mm respectively, each with wide wing shares. This combination has proved to require less power than a single long tine. It still requires up to 100 hp per row, so on the Minnaar farm the 5-row is pulled by a John Deere 9570 RX 4-Track rated at 570 hp.

Tines working at 3 different depths.
Tines working at 3 different depths.

Ripping is done after harvest, this is followed by up to 3 passes with a rod weeder, to remove weeds and, at the same time, germinate weed seeds. One third of the fertiliser, at this stage mainly urea, for the next crop is applied during one of these passes. A John Deere 6140 tractor pulls the 5-row John Deere planter, planting on the row. For the past 12 years the planter has been set up for variable rate seed and fertiliser application. Herbicide is sprayed simultaneously with planting. Variable rate application of lime has been done since 2000.

Maize planted ‘on-the-row’.
Maize planted ‘on-the-row’.

Mr Minnaar fitted his combine with the necessary telemetry to monitor his yields almost 20 years ago. Another third of the total fertiliser requirement, as dictated by the yield maps, is applied by the planter, this is a specific compound, supplied by the fertiliser company in accordance with the various nutrient requirements. The other third, again usually plain urea, is applied as a side dressing when the maize is growing.

No-till no universal silver bullet

Danie Minnaar and his colleagues disagree with some of the more vocal proponents of no-till, who proclaim that this system is a universal ‘silver bullet!’ Mr Minnaar says “The SDC’s trials, conducted with the co-operation of independent agronomists and researchers, have proven the opposite. The matter needs to be approached more cautiously in order to prevent producers suffering serious financial losses by practising no-till in areas that are not suitable.”

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