Maize for Silage
Insight 340


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The maize plant’s development must not be restricted at any stage of growth if maximum yields are to be achieved. The relationship between a crop’s growth and water need can be calculated each week as a percentage of total water needs.

  • 20% in the first five weeks of crop establishment.
  • 33% in the three weeks prior to silking.
  • 31% during the next three weeks during silking and early grain fill.

If an irrigated crop of maize in Canterbury uses nine megalitres of water per hectare in a normal season, up to six megalitres are required (and need to be applied) during the six week period from prior to tasselling to early grain fill.

Table 1: Relationship between age of maize crop and percentage yield reduction due to one day of moisture stress.

The water available each day, or the rate at which that water can be applied to the crop, becomes very important if timeliness of irrigation is to match the crop requirements and not limit yield.

Figure 2: The relationship between water availability and silage yield.

Figure 2 shows that the efficiency of water use increased rapidly as more water was applied (provided population keeps pace) until the hybrid reaches its yield limit (Note: grain yield is approximately 50% of average silage yield).

The soil’s capacity to store moisture is a most important factor as it largely determines the amount and frequency of irrigations and is of paramount importance in deciding yield goals under dryland farming. Table 2 gives the average water storage capacity of various soil types. Work on maize utilising 1.5 m of soil moisture if there are no physical restrictions.

Table 2: Soil water storage capacity

Soil Type

Available water (mm/metre)

Coarse sand

40 mm

Fine sand

100 mm

Fine sand-loam

160 mm


175 mm


215 mm


230 mm

A silty-clay soil wet to 1.5 m holds 325 mm of water (Table 2).


Research clearly shows that the total amount of water used by high yielding crops is only slightly more than that used to produce low yields. Factors that affect this efficiency are:

1. Weed control

Weeds use water that the crop could use. Good weed control improves water use efficiency.

2. Fertiliser

To quote one study, yields from 33 irrigation experiments in Nebraska showed that well fertilised maize averaged approximately 2.5 t/ha more maize than poorly fertilised maize and only used 25 mm extra of water. The well fertilised maize was 43% more efficient in using water. Surprising as it seems, research proves that the total amount of water used by high yielding maize crops is only slightly more than that used to produce low yields. In other words, when you improve your crop management in any way – weed control, hybrid selection, plant population – you grow more maize with a given amount of water.

3. Plant population

Contrary to popular belief, the need for water does not go up directly with increasing plant population. More plants do need a bit more water but they also shade the soil and therefore reduce evaporation and also shade themselves and as a result reduce transpiration (loss from leaf). Figure 2 showed that yield increased at a faster rate than the extra water needed. However, these higher yields are dependent on higher plant populations and it follows therefore that higher plant populations are more efficient users of water.

4. Hybrids

The Pioneer breeding programme has placed heavy emphasis on developing hybrids that will yield well in spite of considerable moisture stress. The relative efficiency of water use under moisture stress of Pioneer maize hybrids is shown in Table 3.

Table 3: Pioneer® brand maize hybrid trait rating score


Score Drought Tolerance

39V43 5
P7524 7
P8000 6
39G12 7
39T45 6
39F58 6
P8805 8
38V12 7


P9400 7
38P05 7
37Y12 6
P9721 8
P9911 9
P0021 7
35A30 7
P0640 7
P0791 9
P0725 9
P0891 8
34P88 7
P1253 7
P1636 7
P1758 7
31G66 8

9 Outstanding,1 Poor


Optimum AQUAmax™ hybrids are exciting products that offer growers additional choices to help minimise risk and maximise crop productivity under drought stress. Developed and tested utilising Pioneer’s extensive drought technology research. Optimum AQUAmax hybrids help deliver a yield advantage in water-limited environments. They:

  • Maximise water access through an extended rooting system.
  • Help minimise the risk of decreased yields due to drought stress.
  • Deliver yield stability even in dry seasons

The first Optumum AQUAmax hybrids for New Zealand are P9241, P9911, P0791, P0725. See your latest Pioneer® brand Maize for Silage catalogue for more details.


So far discussion has centered on the maize plant’s growth and yield under conditions where water is not limiting. With supplementary irrigation, it is essential to understand the effect of moisture stress at various stages of growth. It is generally considered that yield is lost when maize is visibly wilted for four consecutive days. Figure 1 shows tasselling to dough stage as being most susceptible to moisture stress and within that period, silking to blister stage is extremely critical. Consequently, if only one watering can be given, it should be applied just prior to tasselling. If a second one can be applied, it should follow the one at tasselling and be timed to prevent wilting. Obviously, water should be applied during the early stages of growth if the crop is in acute stress and then hope for the best at flowering time. 

When maize plants become stressed, the lower parts of the plant wilt and suffer damage proportionately more than the upper parts. With some hybrids, this has the serious effect of slowing the development of the silks much more than the tassel. This results in the pollen being spent before the silks emerge and little or no grain is formed on the cobs.  Hybrid selection is therefore more important in dryland or limited irrigation situations. 


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The information in this publication is general in nature only. Although the information in this publication is believed to be accurate, no liability (whether as a result of negligence or otherwise) is accepted for any loss of any kind that may arise from actions based on the contents of this publication.

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Revised: June 2016
Expires: June 2017