Effect of NPK Fertilizer on Growth of Amaranthus gangeticus through Fertigation using Burnt Paddy Husks

Abstract

Amaranthus gangeticus (red spinach) is a nutrient-rich leafy vegetable widely grown in Asia, and fertigation offers an efficient approach to deliver nutrients directly to crops. In Malaysia, burnt paddy husks serves as a cost-effective soilless medium, but the impact of different nitrogen, phosphorus and potassium (NPK) fertilizer levels on A. gangeticus growth under fertigation remains underexplored. This study aimed to investigate the effects of different concentrations of water-soluble NPK (20-20-20) fertilizer on the growth of A. gangeticus using fertigation with burnt paddy husks as the medium. Leaf count, plant height and plant weight were measured as important growth indicators. Experiments looked at how A. gangeticus reacted to a fertigation application of an NPK (20-20-20) compound fertiliser under the local agroecological conditions at MARDI Alor Setar. Here, instead of using soil, the substrate used were burnt paddy husks. No NPK was used in one sub-plot 0 g (control) and 10, 15, 20, 25 and 30 g of NPK were used in the remaining sub-plots. The number of leaves and plant height (cm) were recorded weekly over a four-week period. Repeated measures ANOVA showed that both NPK concentration (F = 28.01, p = 0.0001) and time (F = 60.38, p = 0.0001) had significant effects on plant height and leaf count, while their interaction was not significant (F = 0.517, p = 0.613), indicating consistent influence across traits. Pearson correlation analysis showed moderate positive relationships between NPK levels and plant growth, with r = 0.393 for leaf number, r = 0.416 for height, and r = 0.598 for weight. These results also suggest that applying up to 25 g of NPK under fertigation can significantly enhance plant growth and productivity, serving as a valuable guideline for farmers aiming to optimize yield in terms of foliage, height, and weight.