ABSTRACT
Growth, yield and potassium dynamics of konjac (Amorphophallus muelleri Blume) under different shading and potassium fertilization rates

Muhammad Najib Othman Ghani1, 2, Martini Mohammad Yusoff1*, Arina Shairah Abdul Sukor3, Juju Nakasha Jaafar1, Azizah Misran1, and Zulkarami Berahim4
 
Konjac (Amorphophallus muelleri Blume) is a tuberous species that thrives in Malaysian forests and has substantial commercial potential. Despite its importance, agronomic practices that suited with local climate is still scarce. Optimizing key agronomic practices such as shade and K rates require a clear understanding of how they affect plant growth and nutrient dynamics, and how these effects, in turn, influence yield. A field experiment was conducted and treatments of four K rates – 0 (T1), 75 (T2), 150 (T3), 225 (T4) kg ha-1 were nested in three shading rates – 0%, 50%, 70%. Under each shading, each K rate was arranged in a randomized complete block design (RCBD) with four replicates. Regardless of K rates, plants under 70% shading had enhanced growth (leaflet area, petiole diameter), 33.1% more rapid K uptake and 27.9% higher corm yield (P ≤ 0.01; α = 0.05), attributed to 15.71% higher photosynthesis rates compared to plants under 50% shading. For nested effects, under 70% shading, T3 was optimum since K uptake and growth was delayed in T4 plants and the corm yield showed nonsignificant difference to T3. Under 50% shading, yield in T4 plants were significantly (P ≤ 0.01; α = 0.05) higher (46.4%) compared to T3 plants, demonstrating that under less favourable shading, higher K rate (225 kg ha-1) is needed to increase the yield. Soil K content across growth stages follows quadratic function and the optimum time for K fertilization which can enhance its uptake efficiency under the recommended 70% shading rate is 9-10 wk after planting.
Keywords: Dry matter, fertilizer, konjac, potassium rates, potassium uptake, shading.
1Universiti Putra Malaysia, Faculty of Agriculture, Department of Crop Science, 43400 Serdang, Selangor, Malaysia.
2Industrial Crop Research Centre, MARDI Headquarters, Persiaran MARDI-UPM, 43400 Serdang, Selangor, Malaysia.
3Universiti Putra Malaysia, Faculty of Agriculture, Department of Land Management, 43400 Serdang, Selangor, Malaysia.
4Universiti Putra Malaysia, Institute of Tropical Agriculture and Food Security, 43400 Serdang, Selangor, Malaysia.
*Corresponding author (martinimy@upm.edu.my)