ISHS Acta Horticulturae 700: International Symposium Towards Ecologically Sound Fertilisation Strategies for Field Vegetable Production
UNDERSTANDING WATER MOVEMENT IN MULCHED BEDS ON SANDY SOILS: AN APPROACH TO ECOLOGICALLY SOUND FERTIGATION IN VEGETABLE PRODUCTION |
| Authors: | E. Simonne, D. Studstill, R.C. Hochmuth |
| Keywords: | drip irrigation, best management practice, irrigation scheduling, wetted zone |
| DOI: | 10.17660/ActaHortic.2006.700.28 |
| Abstract:
The combined value of tomato, pepper, strawberry and watermelon grown in Florida exceeded $700 million on 30.000 ha in 2003. Drip-irrigation management affects yield and quality of these vegetables as they are grown under intensive fertilization and irrigation. The importance of irrigation management has recently increased as regulation requires vegetable growers to conserve water and reduce nitrate (NO3) discharge into the environment. Hence, the goal of this project was to determine wetting pattern from common drip tapes on a fine sandy soil and for increasing irrigation volumes (V) using a blue dye. Dye tests consisted in preparing mulched beds with different drip tapes, injecting dye, irrigating with the selected V, digging longitudinal and transverse sections of the raised beds, and taking measurements. After digging, wetted zones appeared as blue rings under each emitter. Increasing V from 305 to 2.430 L/100 m significantly increased depth (D, cm) and width (W, cm) of the wetted zone and emitter-to-emitter coverage (L, cm). Depth and W responses to V were D = 0.017 V + 13.7 (R2=0.92) and W = -0.000003 V2 + 0.017 V + 17.6 (R2=0.94). Highest W was 38 cm, which was only 57% of the 71-cm wide beds and may be limiting the use of some drip-injected fumigants. Complete emitter-to-emitter coverage was reached between 2 and 3 h for drip tapes with 30-cm emitter spacing. The wetted front was below the 30-cm depth (typical maximum root depth) when V was 900 to 950 L/100 m, which represents the greatest V that should be applied in a single irrigation event. When soluble KNO3 was injected with the dye, NO3-N concentration was significantly higher in the wetted area and in the dye ring (18 mg.kg-1 soil for both) than below it (3 mg.kg-1) for V ranging between 152 and 610 L/100 m. With larger V, no significant difference was observed in NO3-N concentration inside, on and below the wetted front (all 3 mg kg-1). Hence, the risk of NO3 leaching on a sandy soil may be reduced by using drip tapes with a 20 to 30-cm emitter spacing and irrigation events less than 900 L/100 m each. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
