Effect of Potassium Chlorate Concentration on Flower Initiation of Longan (Dimocarpus longan Lour.) in Soi Dao District, Chanthaburi. Benjaporn Tangsukkasemsan Faculty of Agricultural Technology, Rambhai Barni Rajabhat University, Chanthaburi, Thailand.

Chanthaburi Location Eastern part of Thailand 245 km from Bangkok Area : 6,338 km2

Introduction Longan (Dimocarpus longan Lour.) , cultivar “Daw” an economic crop of Thailand Fresh eaten preserved: canning / dried

Products

longan require a period of cool and dry climatic conditions for induction of flowering northern provinces i.e : Lumpun, Chiang Mai and Chiang Rai.

longan growers have discovered an alternative method of floral induction in the absence of suitable climatic conditions. application of chlorate compound : potassium chlorate or sodium chlorate

Chanthaburi

Plantation and Yield 1996 -2007 Year Planting Area (acre) Harvested area (acre)  total Yield (ton) Average yield/Acre   1996 4,102 1,965 1,979 1007 1997 3,982 1,907 1,918 1005 1998 4,238 2,611 6,301 2412 1999 4,999 3,649 2000 5,648 4,294 19,047 4360 2001 8,062 19,273 4487 2002 11,058 5,460 27,051 4955 2003 12,620 6,930 34,813 5025 2004 19,378 9,948 49,782 5000 2005 32,462 20,724 104,467 5040 2006 33,130 21,813 103,798 4757 2007 33,462 26,789 129,867 4847

Suggestion rate Subhadrabandhu and Yapwattanaphun, (2000): Cultivar 'Daw' requires 8 g/m² of potassium chlorate as soil drench Somchai Ongprasert and Winai Wiriya-Alongkorn (2007) : 200 mg of potassium chlorate per liter of standard nutrient solution

C. Sritontip et. al. : soil drenched with KClO3 at 5 g/m-2 of canopy of 4-5 year- old- longan trees Mike A. Nagao and Elodie B. Ho-a. (2000) : application of 250 – 500 grams of KClO3 around the canopy Li XiangHong (2004) :130 g/m2 seven-year-old trees of longan cultivars Chuliang and Shixia

Chanthaburi growers practice soil drench 200 grams/tree for the 4-year- old- trees By the following years, the amount of potassium chlorate used was double. Shortening longan tree life

The purposes of the study was to determine the suitable amount of KClO3 which were able to initiate flower buds of 7- year- old - longan tree.

Materials and Method completely randomized design 6 treatments and 5 replications. Treatment: 200 gm /50 L water/tree 400 gm/50 L water/tree 600 gm/50 L water/tree 800 gm/50 L water/tree 1000 gm/50 L water/tree 1000 gm/30 L water /tree (control)

experimental units Thirty longan trees seven-year- old Fifty healthy vegetative shoots/tree The potassium chlorate was applied on June 13, 2007.

Result : Days flowering shoots observed KCLO3 concentration days ns 200 gm/ 50 l water/tree 35.46 400 gm/ 50 l water/tree 29.35 600 gm/ 50 l water/tree 32.62 800 gm/ 50 l water/tree 37.25 1000 gm/ 50 l water/tree 39.96 1000 gm/ 30 l water/tree 33.83

Result : Percentage of flowering shoot KCLO3 concentration flowering shoot (%)ns 200 gm/ 50 l water/tree 52.00 400 gm/ 50 l water/tree 53.20 600 gm/ 50 l water/tree 72.80 800 gm/ 50 l water/tree 54.80 1000 gm/ 50 l water/tree 48.40 1000 gm/ 30 l water/tree 69.20

Yield of logan: Mean index KCLO3 concentration Mean index #1ns #2 ns #3 ns #4 ns #5 ns 200 gm/ 50 l water/tree 3.8 2.2 3.0 1.6 2.0 400 gm/ 50 l water/tree 1.4 4.0 1.2 2.4 600 gm/ 50 l water/tree 2.6 800 gm/ 50 l water/tree 3.2 1000 gm/ 50 l water/tree 2.8 4.2 1000 gm/ 30 l water/tree

yield index 1 = none 2 = yield 1-20 % 3 = yield 21-40 % 4 = yield 41-60 % 5 = yield 61-80 % 6 = yield 81-100 %

Yield of logan: mean weight per tree (kg) KCLO3 concentration Mean weight /tree (kg) #1ns #2 ns #3 ns #4 ns #5 ns total 200 gm/ 50 l water/tree 25.80 13.84 12.70 4.50 4.46 61.30 400 gm/ 50 l water/tree 4.76 43.50 26.04 3.20 3.32 80.82 600 gm/ 50 l water/tree 15.00 14.02 26.20 2.00 8.40 65.62 800 gm/ 50 l water/tree 8.72 20.40 21.00 2.84 6.72 59.68 1000 gm/ 50 l water/tree 13.44 3.08 31.20 3.80 3.18 54.70 1000 gm/ 30 l water/tree 9.30 20.90 35.10 2.28 7.18 74.76

conclusion the average flower initiation period was 29-40 days. The application of 600 grams of KClO3/ 50 liters of water/tree give the highest percent of flowering shoot. Not only flower initiation period but also percent of flowering shoot were non-significant.

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