Effect of Drip Irrigation Systems, Water Regimes and Irrigation Frequency on Growth and Quality of Potato under Organic Agriculture in Sandy Soils

Drip irrigation frequency is a recent concept where small frequent irrigation applications are applied to saturate the soil and meet the plant water requirements. A field experiment was carried out during the two summer growing seasons 2006 and 2007, it was executed in Abo-Ghaleb farm, Cairo- Alex. Rood, 60 Km away from Cairo in sandy soil. Seed tubers were planted on 2 th of February and harvested on 28 th of May in the two seasons, and a well water was used as irrigation source having EC 1.9 ds/m. Soil samples were taken up to 45 cm depth. Diameter of the lateral line was 16 mm, with dripper discharge of 2 l/h. The present investigation aimed to study the effect of drip irrigation systems, water regimes and irrigation frequency on the growth and quality of potato under organic agriculture. The following parameters were studied to evaluate the performance of the studied factors; and the interaction between them (1) growth of potato, (2) quality of potato. The results indicated that growth and quality of potato were improved by increasing irrigation frequency under 100% and 75% from water requirements and decreased at 50 % from water requirements where: growth (shoot/Plant and Leaves area/Plant) where improved by increasing number of irrigation pulses especially at (100% and 75% from water requirements) at all sampling dates. Shoot/Plant increased from 38.22 (gm) under continuous drip irrigation to maximum value, where it became 46.12 (gm) after applying pulse technique with 4 pulses at 100 % from water requirements under subsurface drip irrigation at 100 days from sowing, Also, leaves area/plant increased from 1668 (cm2) under continuous drip irrigation to maximum value, where it became 1875 (cm2) under the same conditions. Dry matter, specific density and total carbohydrates of tubers increased from 14.73%, 1.0540 gm/cm3, 40.52% under continuous drip irrigation to maximum values, where it become 18.99%, 1.0742 gm/cm3, 45.58% respectively after applying drip irrigation frequency with 4 times/day at 100% from water requirements under subsurface drip irrigation