Irrigation
All brassicas require regular, uniform watering during the growing season. Water shortages during establishment can limit seed germination, transplant establishment, and early growth. Inconsistent watering around heading set can cause misshapen, rough broccoli or cauliflower heads, induce splitting or tip burn in cabbage, and affect flavor. Overwatering wastes water and encourages root rots and foliar disease. Sprinklers are regularly used to germinate seed or establish transplants. Then, after the first cultivation, you can switch to furrow irrigation. For small production areas, it is common to use drip irrigation.
Monitor soil water status regularly to maintain consistent, uniform water supply. Use soil moisture monitoring sensors and weather-based irrigation scheduling to monitor plant needs. Place sensors at various locations in the field and at several depths in the soil profile to accurately measure soil water content. Start irrigating at 20% to 25% depletion when irrigating by drip and at 35% to 45% depletion for furrow or sprinkler systems. Water extraction estimates, using reference evapotranspiration adjusted with a crop coefficient (kc), are closely related to row canopy cover in the brassicas. The kc is about 0.3 for a crop with 25% row cover, 0.6 for 50% cover, and 1 for 85% cover. Note that irrigation also depends on your soil type. ATTRA Sustainable Agriculture’s publication Soil Moisture Monitoring: Low -Cost Tools and Methods contains more suggestions for managing soil moisture.
Soil Tension Values for Different Soil Textures
| Soil Texture | 0% |
20-25% |
35-45% |
|---|---|---|---|
| Soil Tension Values (centibars) | |||
| Sand, loamy sand | 5-10 | 17-22 | 25-30 |
| Sandy loam | 10-20 | 22-27 | 33-40 |
| Loam, silt loam | 15-25 | 25-30 | 40-50 |
| Clay loam, clay | 20-40 | 35-45 | 55-65 |
Note. Use in scheduling drip irrigation, based on various percentages of depletion of available water holding capacity (field capacity).