Question
Given the following on crop water requirements for maize under rain fed conditions:
ET0(mm/day)5.96.45.85.6
(b)Determine the crop water requirement for the whole season in m3per hectare.
(c)Did the crop experience any deficit during the season and by how much if any?
(a)Determine the crop water requirement for each growth stage in mm.
(d)How would you use this information in drought-prone areas of Zambia?
(in mm).
Length (Days)25305035
Rainfall (mm)50270305100
Growth stageIIIIIIIV
Kc0.150.751.20.5
ET0(mm/day)5.96.45.85.6
(b)Determine the crop water requirement for the whole season in m3per hectare.
(c)Did the crop experience any deficit during the season and by how much if any?
(a)Determine the crop water requirement for each growth stage in mm.
(d)How would you use this information in drought-prone areas of Zambia?
(in mm).
Length (Days)25305035
Rainfall (mm)50270305100
Growth stageIIIIIIIV
Kc0.150.751.20.5
Answers
GPT-4o mini
To determine the crop water requirements for maize under rain-fed conditions using the provided information, we'll follow these steps:
### Step (a): Calculate the crop water requirement for each growth stage in mm.
1. **Define the parameters:**
- ET₀ values (mm/day): 5.9, 6.4, 5.8, 5.6
- Length of each stage (days): 25, 30, 50, 35
- Crop coefficient (Kc): 0.15, 0.75, 1.2, 0.5
2. **Calculate ETc for each growth stage using the formula:**
\[
ETc = ET0 \times Kc
\]
3. **Growth stage calculations:**
- **Stage I** (25 days, Kc=0.15, ET₀=5.9):
\[
ETc = 5.9 \times 0.15 = 0.885 \, \text{mm/day}
\]
\[
\text{Total} = 0.885 \, \text{mm/day} \times 25 \, \text{days} = 22.125 \, \text{mm}
\]
- **Stage II** (30 days, Kc=0.75, ET₀=6.4):
\[
ETc = 6.4 \times 0.75 = 4.8 \, \text{mm/day}
\]
\[
\text{Total} = 4.8 \, \text{mm/day} \times 30 \, \text{days} = 144 \, \text{mm}
\]
- **Stage III** (50 days, Kc=1.2, ET₀=5.8):
\[
ETc = 5.8 \times 1.2 = 6.96 \, \text{mm/day}
\]
\[
\text{Total} = 6.96 \, \text{mm/day} \times 50 \, \text{days} = 348 \, \text{mm}
\]
- **Stage IV** (35 days, Kc=0.5, ET₀=5.6):
\[
ETc = 5.6 \times 0.5 = 2.8 \, \text{mm/day}
\]
\[
\text{Total} = 2.8 \, \text{mm/day} \times 35 \, \text{days} = 98 \, \text{mm}
\]
### Summary of Crop Water Requirements for Each Growth Stage:
- Stage I: 22.125 mm
- Stage II: 144 mm
- Stage III: 348 mm
- Stage IV: 98 mm
### Step (b): Total crop water requirement for the whole season in m³ per hectare.
1. **Calculate the total water requirement (in mm):**
\[
\text{Total water requirement} = 22.125 + 144 + 348 + 98 = 612.125 \, \text{mm}
\]
2. **Convert mm to m³ per hectare (1 mm = 10 m³/ha):**
\[
\text{Total water requirement (m}^3/\text{ha)} = 612.125 \, \text{mm} \times 10 = 6121.25 \, \text{m}^3/\text{ha}
\]
### Step (c): Determine if the crop experienced any deficits.
1. **Total rain during the season (30 + 30 + 50 + 10):**
\[
\text{Total rainfall} = 50 + 270 + 305 + 100 = 725 \, \text{mm}
\]
2. **Deficit calculation:**
\[
\text{Deficit} = \text{Total water requirement} - \text{Total rainfall}
\]
\[
\text{Deficit} = 612.125 \, \text{mm} - 725 \, \text{mm} = -112.875 \, \text{mm}
\]
*Since this is negative, there was no deficit; in fact, there was a surplus of 112.875 mm.*
### Step (d): Using this information in drought-prone areas of Zambia.
1. **Irrigation Planning:** This data can help in designing irrigation systems where it is required. For example, if the rainfall is consistently lower, the irrigation systems could be planned for the growth stages that are most critical for maize.
2. **Water Management:** Knowing the total crop water requirement can help farmers manage and conserve water, allowing them to allocate it more effectively throughout the growth stages.
3. **Drought Mitigation:** Understanding the crop's water needs relative to expected rainfall can help prepare for drought risks and implement practices such as mulching, using drought-resistant seeds, or soil moisture conservation strategies.
4. **Farming Strategies:** In case of expected deficits, farmers can plan to plant early or adjust planting dates based on forecasted weather patterns.
5. **Education and Training:** Farmers can be educated on the importance of monitoring rainfall and irrigation needs, enhancing their ability to respond to variations in climatic conditions.
In conclusion, this analysis provides valuable guidelines for efficient water use in maize cultivation, especially in regions vulnerable to water scarcity.
### Step (a): Calculate the crop water requirement for each growth stage in mm.
1. **Define the parameters:**
- ET₀ values (mm/day): 5.9, 6.4, 5.8, 5.6
- Length of each stage (days): 25, 30, 50, 35
- Crop coefficient (Kc): 0.15, 0.75, 1.2, 0.5
2. **Calculate ETc for each growth stage using the formula:**
\[
ETc = ET0 \times Kc
\]
3. **Growth stage calculations:**
- **Stage I** (25 days, Kc=0.15, ET₀=5.9):
\[
ETc = 5.9 \times 0.15 = 0.885 \, \text{mm/day}
\]
\[
\text{Total} = 0.885 \, \text{mm/day} \times 25 \, \text{days} = 22.125 \, \text{mm}
\]
- **Stage II** (30 days, Kc=0.75, ET₀=6.4):
\[
ETc = 6.4 \times 0.75 = 4.8 \, \text{mm/day}
\]
\[
\text{Total} = 4.8 \, \text{mm/day} \times 30 \, \text{days} = 144 \, \text{mm}
\]
- **Stage III** (50 days, Kc=1.2, ET₀=5.8):
\[
ETc = 5.8 \times 1.2 = 6.96 \, \text{mm/day}
\]
\[
\text{Total} = 6.96 \, \text{mm/day} \times 50 \, \text{days} = 348 \, \text{mm}
\]
- **Stage IV** (35 days, Kc=0.5, ET₀=5.6):
\[
ETc = 5.6 \times 0.5 = 2.8 \, \text{mm/day}
\]
\[
\text{Total} = 2.8 \, \text{mm/day} \times 35 \, \text{days} = 98 \, \text{mm}
\]
### Summary of Crop Water Requirements for Each Growth Stage:
- Stage I: 22.125 mm
- Stage II: 144 mm
- Stage III: 348 mm
- Stage IV: 98 mm
### Step (b): Total crop water requirement for the whole season in m³ per hectare.
1. **Calculate the total water requirement (in mm):**
\[
\text{Total water requirement} = 22.125 + 144 + 348 + 98 = 612.125 \, \text{mm}
\]
2. **Convert mm to m³ per hectare (1 mm = 10 m³/ha):**
\[
\text{Total water requirement (m}^3/\text{ha)} = 612.125 \, \text{mm} \times 10 = 6121.25 \, \text{m}^3/\text{ha}
\]
### Step (c): Determine if the crop experienced any deficits.
1. **Total rain during the season (30 + 30 + 50 + 10):**
\[
\text{Total rainfall} = 50 + 270 + 305 + 100 = 725 \, \text{mm}
\]
2. **Deficit calculation:**
\[
\text{Deficit} = \text{Total water requirement} - \text{Total rainfall}
\]
\[
\text{Deficit} = 612.125 \, \text{mm} - 725 \, \text{mm} = -112.875 \, \text{mm}
\]
*Since this is negative, there was no deficit; in fact, there was a surplus of 112.875 mm.*
### Step (d): Using this information in drought-prone areas of Zambia.
1. **Irrigation Planning:** This data can help in designing irrigation systems where it is required. For example, if the rainfall is consistently lower, the irrigation systems could be planned for the growth stages that are most critical for maize.
2. **Water Management:** Knowing the total crop water requirement can help farmers manage and conserve water, allowing them to allocate it more effectively throughout the growth stages.
3. **Drought Mitigation:** Understanding the crop's water needs relative to expected rainfall can help prepare for drought risks and implement practices such as mulching, using drought-resistant seeds, or soil moisture conservation strategies.
4. **Farming Strategies:** In case of expected deficits, farmers can plan to plant early or adjust planting dates based on forecasted weather patterns.
5. **Education and Training:** Farmers can be educated on the importance of monitoring rainfall and irrigation needs, enhancing their ability to respond to variations in climatic conditions.
In conclusion, this analysis provides valuable guidelines for efficient water use in maize cultivation, especially in regions vulnerable to water scarcity.