- Under irrigation a good commercial grain yield is 6 to 9 ton/ha (10 to 13 percent moisture).
- The water utilization efficiency for harvested yield (Ey) for grain varies then between 0.8 and 1.6 kg/m3.
The graph below depicts the crop stages of maize, and the table summarises the main crop coefficients used for water management.
Stages of Development | Plant date | Region | |||||
---|---|---|---|---|---|---|---|
Crop | Initial | Crop Development | Mid-season | Late | Total | ||
Stage length, | 30 25 20 20 30 30 30 | 50 40 35 35 40 40 40 | 60 45 40 40 50 50 50 | 40 30 30 30 30 30 50 | 180 140 125 125 150 150 170 | April Dec/Jan June Oct./Dec April April April | East Africa (alt.) Idaho, USA |
Depletion Coefficient, p | 0.50 | 0.50 | 0.50 | 0.80 | – | ||
Root Depth, m | 0.30 | >> | >> | 1.00 | – | ||
Crop Coefficient, Kc | 0.30 | >> | 1.2 | 0.5 | – | ||
Yield Response Factor, Ky | 0.40 | 0.40 | 1.30 | 0.50 | 1.25 |
Stages of Development | |||||
---|---|---|---|---|---|
Crop characteristic | Initial | Crop Development | Mid-season | Late | Total |
Stage length, days | 25 | 40 | 40 | 35 | 135 |
Depletion Coefficient, p | 0.50 | 0.50 | 0.50 | 0.80 | – |
Root Depth, m | 0.30 | >> | >> | 1.00 | – |
Crop Coefficient, Kc | 0.30 | >> | 1.2 | 0.5 | – |
Yield Response Factor, Ky | 0.40 | 1.0.40 | 1.30 | 0.50 | 1.25 |
Maize is an efficient user of water in terms of total dry matter production and among cereals it is potentially the highest yielding grain crop.
For maximum production a medium maturity grain crop requires between 500 and 800 mm of water depending on climate.
To this, water losses during conveyance and application must be added.
This schematic graph shows the growth periods of maize.
The relationships between relative yield decrease (1 – Ya/Ym) and relative evapotranspiration deficit for the total growing period are shown in the figure below.
This figure shows the relationships between relative yield decrease (1 – Ya/Ym) and relative evapotranspiration deficit for the individual growth periods.
The effect of limited water on maize grain yield is considerable and careful control of frequency and depth of irrigation is required to optimize yields under conditions of water shortage.
Where water supply is limited it may therefore be advantageous to meet, as far as possible, full water requirements (ETm) so as to achieve near maximum yield from a limited acreage rather than to spread the limited water over a larger acreage.
Maize flourishes on well-drained soils and waterlogging should be avoided, particularly during the flowering (2) and yield formation (3) periods.
Waterlogging during flowering (2) can reduce grain yields by 50 percent or more.
To obtain a good stand and rapid root development, the root zone should, where feasible, be wetted at or soon after sowing.