Technology [photo] 


Implications of OmniPrecise™ and optimum fertilizer practices in the North Western maize producing area


The past planting season was in many respects one of the most difficult in years. Firstly conditions before planting – during the soil preparation period – was very wet, which hampered primary soil tillage. The first rains fell relatively late and this put pressure on the planting process. Lastly, the follow-up rain later in the season was very little and therefore crops entered the critical flowering phase during warm, dry conditions.

Nevertheless, there were still farmers who harvested excellent yields. Most of these successes under such difficult circumstances are due to the effective application of precision farming practices. The purpose of this article is therefore to firstly demonstrate how OmniPrecise™ is implemented in practice. Secondly we will look at results of a fertilizer trial (called High Yield Trial, or HYT). Lastly we will attempt to determine if precision fertilization is more effective than general fertilization.

General OmniPrecise applications

A specific client in the Schweizer-Reneke area has for the last four years been making use of the total precision farming package. This involves the following aspects:

  1. Physical and chemical mapping of the soil on a 1-ha grid (Fig. 1)
  2. The differential correction of soil acidity (Fig. 3 (a) and (b))
  3. The compilation of potential maps and collection of yield data (Fig. 5 and 6)
  4. The incorporation of above mentioned data in order to compile variable fertilizer maps (Fig. 4)
  5. The evaluation and verification of results in order to make use of optimal fertilization and plant population practices in the coming season.

Figure 1 shows the soil map of the relevant field where the HYT trials weer conducted during the previous season. For every one of the different soil types and soil classes, a specific soil potential is awarded by means of a crop growth stimulation model.

Figure 1. Soil map as compiled by OmniPrecise™

Soil map as compiled by OmniPrecise™ [chart]

If the soil map and resulting potential zones show certain soil types which cannot be cultivated economically under dryland conditions, these areas of the field will be withdrawn. The next step will be to address chemical deficiencies / imbalances.

In most cases this will include a variable lime application, as can be seen for this specific field in Figure 3 (a) and (b).

Figure 3 (a). Liming map (top part of the trial block)

Liming map top [chart]

Figure 3 (b). Liming map (bottom part of the trial block)

Liming map bottom part [chart]

The water holding capacity of the soil was of the utmost importance during the past season (Figure 2). Due to the fact that it didn't rain often during the season, the maize was very dependent on this previously stored moisture. The largest part of the field lay fallow during the previous season and, combined with the little rain, the yield map (Figure 5), looked very similar to the plant available water capacity map (Figure 2).

Figure 2. Soil water holding capacity

Soil water holding capacity [chart]

Except for the trial location (HYT), fertilizer was applied variably before planting in the soil on both sides of the planting row this past season. The variable application map was compiled according to the soil potential which was calculated by OmniPrecise. This map can be seen in Figure 4. When the variable application map (Figure 4) is compared to the resulting yield map (Figure 5), the good correllation between the two maps can clearly be seen. Therefore the areas with a lower yield received less fertilizer during the past season,whereas the high yielding areas received considerably more.

This resulted in a much higher fertilizer use efficiency as with conventional fertilizer application.

Figure 5. Yield map for the 2011/ 2012 season

Yield map for the 2011/ 2012 season [chart]

Figure 4. Variable application rate map 2011/2012 season

Variable application rate map 2011/2012 season [chart]

Client practices

The client grows mainly maize and sunflower planted in a rotation and fallow system. Controlled traffic and stubble mulching are applied where possible, as wind erosion remains a great risk on the mostly sandy soils. Primary tillage is done using a deep rip action. Depending on the clay percentage, this will be done between 450 and 700 mm deep. As mentioned before, soil acidity is corrected using lime every four to five years after the soil samples are taken on a one hectare grid and chemically tested and processed (as seen in figure 3 (a) and (b)). A six row train track plant row width of 1.1 m is used. Weed control is done both mechanically and chemically.

High Yield Trial (HYT)

This year the so-called High Yield Trials (HYT) were conducted all over the Omnia North West Business Unit's service area again for the sixth consecutive season. The aim of these trials is to determine the economic and yield curve for every region with increasing plant nutrition applications. The most difficult season was also the ideal opportunity to prove the sceptics wrong once again corcerning the optimal fertilization according to the soil's inherent yield potential and prevailing climate conditions.

On all the blocks part of the fertilizer was applied beforehand in the soil in the form of Urea (46), 1:1:1 (27) 0.5% Zn and Greensulf 35, after which 21:8:0 (29) Plus was used at planting and the rest applied as an LAN (28) topdressing. The trial was planted on 22 November 2011 using the cultivar DKC 78-45BR at a planting population of 26,000 plants per hectare. The different fertilizer treatments were as follows (Table 1):

Table 1: HYT fertilizer treatments
1       0 0 0    
2 150 21:8:0(29) 0.5%ZN 8S Plus   31.50 12.0 0.0 0.75 12
  62 Ureum(46) / Urea(46)   28.52 0.0 0.0 0.0 0.0
  0 1:1:1(27)+GS(35)   0.0 0.0 0.0 0.0 0
  0 KAN(28) / LAN(28)   0.0 0 0.0 0.0 0
      Total 60.02 12.00 0.0 0.75 12.00
3 150 21:8:0(29) 0.5%ZN 8S Plus   31.50 12.0 0.0 0.75 12
  90 Ureum(46) / Urea(46)   41.40 0.0 0.0 0.0 0.0
  105 1:1:1(27)+GS(35)   17.02 5.4 5.4 0.30 5
  0 KAN(28) / LAN(28)   0.0 0 0.0 0.0 0
      Total 89.92 17.44 5.4 1.05 17.46
4 150 21:8:0(29) 0.5%ZN 8S Plus   31.50 12.0 0.0 0.75 12
  82 Ureum(46) / Urea(46)   37.72 0.0 0.0 0.0 0.0
  175 1:1:1(27)+GS(35)   28.37 9.1 9.1 0.51 9
  80 KAN(28) / LAN(28)   0.0 0 0.0 0.0 0
      Total 119.99 21.07 9.1 1.26 21.10
5 150 21:8:0(29) 0.5%ZN 8S Plus   31.50 12.0 0.0 0.75 12.00
  125 Ureum(46) / Urea(46)   57.50 0.0 0.0 0.0 0.0
  240 1:1:1(27)+GS(35)   38.90 12.43 12.43 0.70 12.48
  80 KAN(28) / LAN(28)   22.40 0.00 0.00 0.00 0.00
      Total 150.30 24.43 12.4 1.45 24.48
6 150 21:8:0(29) 0.5%ZN 8S Plus   31.50 12.0 0.0 0.75 12.00
  165 Ureum(46) / Urea(46)   75.90 0.0 0.0 0.0 0.0
  310 1:1:1(27)+GS(35)   50.25 16.06 16.06 0.90 16.12
  80 KAN(28) / LAN(28)   22.40 0 0.0 0.0 0
      Total 180.05 28.06 16.1 1.65 28.12

According to Figure 5, the area where the trial was planted is shown by two black lines. Every treatment was replicated twice, except for the "no fertilizer", which was only replicated once. Looked at more closely, every planting lane's yield looked as follows:

Figure 6: Yield data of trial area (raw data as measured per plant/ harvest lane)

XXXX [chart]

During the harvesting of the trial, as well as is clear from the above yield monitor map, the reaction to the different fertilizer treatments was outstanding. The specific yields of every treatment, as well as the yields to either side of the treatments where the farmer applied his variable fertilizer, is given in Table 2:

Table 2: Specific yields of HYT treated lanes
HYT trial S/R 2011/2012    
TreatmentReplicate 1Replicate 2Ave
N P K S Ave Max Ave Gem Ave Min  
0 3.21 5.47 1.7       3.21
60 12 0 12 5.44 10.68 2.08 5.56 11.95 2.13 5.50
90 17 5 17 7.04 10.36 3.19 6.95 9.96 3.61 7.00
120 21 9 21 8.06 10.19 3.85 7.76 10.66 3.6 7.91
150 24 12 24 8.75 10.78 2.06 8.82 10.9 5.34 8.79
180 28 16 28 9.1 13.38 2.06 9 11.25 2.17 9.05
120 21 9 21
8.54 9.9 2.7 8.77 10.73 3.75 8.66

In Graph 1 the impact of the different fertilizer treatments on the yields can clearly be seen, as well as the margin above fertilization costs. The 150N, 28P, 16K and 18S treatments generated the highest profits, with R14,655/ha after the specific fertilizer costs had been deducted and using a maize price of R2,000/ton.

Graph 1. Yield and profitability of different N:P:K:S applications

Yield and profitability of different N:P:K:S applications [chart]

The rainfall measured for the season at the trial site is shown in Table 2.

Rainfall 2011/2012
HOP / HYT S/R   
Nov 20 27  
  22 4  
  29 12 43
Dec 6 3  
  7 21  
  9 22  
  10 30  
  24 74 150
Jan 6 8  
  11 32  
  22 34 74
March 23 20 20
Total     287

Variable or constant fertilizer applications?

As can be seen from Table 3, it was a very dry season. Despite this, the reaction to the different fertilizer rates remained phenominal. Yields kept on increasing with increasing fertilizer rates, with the highest yield of more than 9 tonnes/ha using the maximum application. However, if the economic implications of the trial is considered, the maximum profit was obtained with the 150 kg/ha N treatment. As mentioned, the fertilizer on the rest of the field was applied variably, using all of the above information. On either side of the HYT the average fertilization was the same as the 120N treatment. The variable 120 kg/ha N yielded 750 kg/ha more than the constant 120 kg/ha treatment – therefore almost the same as the constant 150 kg/ha N treatment.

Six rows of 0 fertilizer 9 weeks after emergence [chart]

Photo 1: Six rows of 0 fertilizer 9 weeks after emergence. To the right of the centre rows 120 kg/ha N was variably applied and to the left was the 60 kg/ha N treatment.

Six rows of the 150 kg/ha N treatment 9 weeks after emergence [chart]

Photo 2: Six rows of the 150 kg/ha N treatment 9 weeks after emergence.

Six rows of 0 fertilizer treatment 14 weeks after emergence [chart]

Photo 3: Six rows of 0 fertilizer treatment 14 weeks after emergence, with the 120 kg/ha variable N treatment to the right and the normal 60 kg/ha N treatment to the left of the two centre rows.

Six rows of the 150 kg/ha N treatment 14 weeks after emergence [chart]

Photo 4: Six rows of the 150 kg/ha N treatment 14 weeks after emergence.


Except for the excellent yield increase obtained using the increasing fertilization rates, the yield obtained in the variable treatments just confirms that in the difficult farming environment of today, technology exists which can significantly improve the optimal use of fertilizer – even in a very dry season! Therefore, by using all the tools that Omnia offers, the client can optimise the profits from his soil, in spite of difficult circumstances.

If you, as a crop producer, have not made use of this technology yet, you have room to optimise even more. Speak to your Omnia agronomist. He can help you to implement this process on your farm and optimise your profitability.

By Stefan de Jager 082 376 8915