Effects of Application Rate and Timing of Slow-release Fertilizer and Supplemental Potassium on Yield of Greenhouse-grown Ginger

Ginger (Zingiber officinale) is a high value tropical spice crop with great potential to be grown under greenhouse conditions during any time of the year in temperate climates. Production of ginger under weather controlled environments using soilless substrate is also a way to avoid soil born diseases such as bacterial wilt (Ralstonia solanacearum). The proper application of fertilizer is important to obtain a high yield; however, there is no clear guideline on the optimum rate of fertilizers for the production of ginger. Potassium (K) is a major source of nutrition in ginger, and one of the most important limiting factors for ginger production. Main objectives of the studies were to assess proper application rates and timings of base fertilizer (13N:13P:13K) and K supplement to strategically provide fertilizers to ginger in order to achieve greater yield and increase nutrient use efficiency. Ginger rhizomes pieces were planted in 7 gallon containers filled with commercial substrate (Sungro professional growing mix). Four different rates of base fertilizer (112, 168, 200, and 234 g/container in total), were split and applied at three different times: 0, 2.5 and 4.5 months after planting (MAP). We found that the medium level of fertilizer (168 g/container) produced the highest rhizome yield, while higher levels of fertilizer significantly reduced the yield of rhizomes. A follow-up research was conducted to supplement K at three different rates (0, 50 and 100g/container) and times (0, 2.5 and 4.5 MAP) in addition to the base application of medium rate fertilizer. The application with increasing K rate significantly increased rhizome yield. The highest yield was obtained when K supplement (100 g) was split and applied at 2.5 and 4.5 MAP, however, when applied only once at either time, it had no impact or a negative impact on yield. These results indicate that the application rate and timing of base fertilizer and supplemental K is critical, and a split application of K supplement in combination with the optimum rate of base fertilizer is an effective strategy to maximize the yield of greenhouse-grown ginger.