Fertigation regimes for seed rhizome production in ginger (Zingiber offcinale Roscoe)

Abstract

The study entitled “Fertigation regimes for seed rhizome production in Ginger (Zingiber officinale Roscoe)” was carried out inside a naturally ventilated 400 m² polyhouse at RARS, Pattambi, during the period 2024–2025 (Kharif season), with the objective of evaluating the effect of different fertigation regimes on seed rhizome production in ginger. Throughout the growth period, polyhouse conditions averaged 75% relative humidity, 32–35 °C temperature and 4470–8040 lux light intensity during noon hours. The study used the ginger variety ‘Athira’, which was propagated through micro rhizomes obtained from the Centre for Plant Biotechnology and Molecular Biology (CPBMB), College of Agriculture, Vellanikkara. The plants were grown in polybags filled with solarized potting media (soil, sand, coir pith and farm yard manure in equal parts). The experiment was conducted using a Completely Randomized Design (CRD) with six fertigation regimes with three replications. The treatments consisted of the recommended dose of fertilizer (RDF: 0.94:0.63:0.63 g NPK per plant) applied up to 300 days of planting following the conventional split schedule (T₁), RDF applied up to 240 days of planting using a modified split method (T₂), a 10% increase in RDF with the conventional split application (T₃), a 10% increase in RDF following the modified split schedule (T₄), a 20% increase in RDF under the conventional split application (T₅) and a 20% increase in RDF applied through the modified split method (T₆). Nutrients were supplied through fertigation using 19:19:19, urea, potassium nitrate and monoammonium phosphate. Data were collected on growth, physiological traits, quality attributes and rhizome characteristics. Plant growth parameters were recorded at monthly intervals. Observations were recorded on major growth parameters, including plant height, number of leaves per tiller, number of tillers, tiller diameter, leaf length, leaf width, leaf area, internodal length and the fresh and dry matter production of shoots and roots. Among the treatments, T2 (RDF with split application up to 240 days of planting) recorded the highest tiller count (29.87). The T6 (20% higher RDF with split application up to 240 days of planting) showed superiority in plant height (124.92

cm), leaf length (27.69 cm), leaf area (43.63 cm²) and also recorded the highest shoot fresh weight (746.67 g) and dry weight (121.67 g) at 180 days after planting (DAP). The T5 (20% increased RDF) produced the maximum number of leaves (27.80), the highest root fresh weight at 180 DAP (158.34 g) and at harvest (141.67 g), the highest root dry weight at 180 DAP (43.34 g) and the greatest tiller diameter (0.98 cm). The maximum internodal length (6.13 cm) was recorded in T3 (10% increased RDF), which was statistically on par with T2 (RDF with split application up to 240 days of planting) (6.04 cm). Rhizome characters were analyzed at the 8 months after planting (MAP). Rhizome fresh and dry weights, finger numbers, finger length, finger girth, number of nodes per finger and internodal length of fingers were recorded at the time of harvest. The T₂ (RDF with split application up to 240 days of planting) recorded the highest rhizome fresh weight (400.33 g), dry weight (85.00 g) and volume (368.00 cc). It produced the maximum number of primary (8.87) and secondary fingers (22.33), with the greatest finger length (12.34 cm in primary and 3.24 cm in secondary), girth (2.75 cm in primary and 1.74 cm in secondary), nodes per finger (21.35 in primary and 5.57 in secondary) and internodal length (0.80 cm in primary and 0.57 cm in secondary). The driage percentage of ginger at harvest was not significantly affected by the different fertigation regimes. Fertigation regimes significantly influenced leaf nutrient status at 5 MAP. The highest leaf nitrogen content was observed in T₅ (3.62 %), followed by T₆ (3.15 %). Phosphorus concentration was highest in T₂ (0.30 %), while potassium content was maximum in T₁ (3.35 %) and T₃ (3.28 %), which were statistically at par. Chlorophyll content was recorded at 5 MAP. T₆ recorded the highest chlorophyll a (1.39 mg g⁻¹), chlorophyll b (0.99 mg g⁻¹) and total chlorophyll (2.37 mg g⁻¹) contents. Quality parameters of rhizomes were recorded at harvest, with volatile oil content highest in T₄ and T₆ (3.25%) and oleoresin concentration highest in T₆ (7.65%). Senescence was observed at 240 DAP, with 100% flowering. Throughout the growing season, no occurrence of soft rot, bacterial wilt or pest infestation was recorded. The study concluded that, for ginger seed rhizome production under polyhouse conditions, a split application of 0.94:0.63:0.63 g NPK per plant up to 240 days of planting is the most effective fertigation regime. It optimizes rhizome yield by supplying nutrients during critical growth and bulking stages, whereas higher nutrient doses primarily enhance vegetative growth.