Studies on Seed Production Techniques of Water Convolvulus (Ipomoea aquatica Forsk.) II. Effect of Planting Dates on the Seed Production Potentiality of Different Cultivars of Water Convolvulus Grown u

Two cultivars of water convolvulus, cv. Pingtung Green Stem(pointed leaf)and cv. White Stem (broad leaf) were planted in paddy and upland fields jn early July, August, September and October of 1978. The days of flowering after planting (DFAP) of these two cultivars indicated shortened period when planted late. They showed similar horticultural characters and seed production potentialities. Cultura 1 conditions (paddy or upland) did not influence flowering time, but there was difference on flowering time of these two cultivars, White Stem flowered earlier than Pingtung Green Stem. Hundred seeds weight was significantly influenced by planting dates, but not by cultural conditions. On the contrary, aye, length of each node per tiller was significantly influenced by cultural conditions, but not by planting dates. Ave. length of tiller per hill, ave. no. of nodes per tiller, no. of flowers per hill, no. of capsules per hill, straw weight, seed yield and grain/straw ratio of water convolvulus were significantly influenced by the planting dates and cultural conditions. Water convolvulus planted in upland conditions showed that the plant vigor and seed production potentiality were better than in paddy fields. Straw weight in upland culture was 6,839 kg/ha, higher than in paddy culture of 3,185 kg/ha. Seed yield was also higher in upland culture of 1,221 kg/ha than in paddy culture of 795 kg/ha. Between different planting dates, straw weight showed highest on July planting of 6,781 kg/ha and lowest on October planting of 3,352 kg/ha. However, seed yield showed highest on August planting of 1,332 kg/ha, second on July planting of 1,284 kg/ha and lowest on October planting of 553 kg/ha. The data showed that both White Stem and Pingtung Green Stem water convolvulus are more favourable for planting on upland condition in Sou-them Taiwan. Suitable planting dates for water convolvulus seed production culture are during late July to early August. This information may be valuable to farmers who are interested in water convolvulus seed production.