Flowering, fruit set and fruitlet drop of durian (Durio zibethinus Murr.) under different soil moisture regimes

M. Masri

Abstract

The effects of different soil moisture levels on flowering, fruit set and fruitlet drop of durian (Durio zibethinus Murr.) of D24 clone were studied under field conditions. Treatments comprising T1 (1 emitter/tree), T2 (2 emitters/tree), T3 (3 emitters/tree) and T4 (4 emitters/tree) were imposed on 8-year-old matured trees, 2 weeks prior to expected flowering and continued thereafter for 60 days. Soil moisture potential (ψs) was used to indicate the water status in the various treatments. T1 was most severely stressed with ψs consistently maintained below –0.5 MPa. T4 had abundant water with ψs fluctuating around –0.1 MPa. Soil moisture status in T2 and T3 treatments were considered moderate with ψ ranging from –0.2 MPa to –0.4 MPa on most of the days. T1 and T4 produced the least number of inflorescence and flowers indicating that continuous water stress or excess supply of water failed to initiate more flowers. It was the T2 and T3 treatments, with moderate water supply, that produced the highest number of inflorescence, flowers and flowers per inflorescence. Fruit set was relatively high (76–88%) and was not influenced by soil moisture status. Plants under restricted soil moisture (T1) had a very high percentage of fruitlet drop, reaching 100% at 5 weeks after fruit set. However, those given moderate (T2 and T3) and abundant water supply (T4) showed a 97–99% fruitlet drop although these percentages were not statistically significant. In summary, water management prior to and during drought is important in ensuring higher yield of durian. More detailed studies on these aspects are critically needed.

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