Phonska Fertilizer Leaching and Its Effect on Spinach Growth and Productivity (Amaranthus tricolor. L) on Latosol with Different Clay Content

Abstract

Sufficient available water in soil is very essential for plant growth, not only as a nutrient solvent but also to maintain
optimal turgor pressure. Occasionally, additional water supply from irrigation is necessary to achieve optimal soil water
,:ondition. The aim of this research was to study leaching of several nutrients correlated to the growth and productivity of
spinach. PHONSKA fertilizer as a source of nutrients was applied to Latosols Darmaga having different clay content. The
treatments were subjected to different level of water supply resulting in different soil moisture regime. Factorial completely
randomized design was used for the experiment; the first factor was clay content. Clay content was differentiated between 81
% clay (very fine clayey) and 51 % clay (fine clayey). The secondfactor was level of water supply (100, 120, 140 and 160 % of
water holding capacity).
The result of this research showed that the interaction between clay content and amount of water supplied significantly
influenced rate of N, P and K leaching, the sum of leached water and also produced plant biomass (P<0.05. The highest
leaching occurred in fine clayey texture with water supply level 160 % of water holding capacity. Meanwhile, treatment with
level of water supply 100 % of water holding capacity did not have leaching. Increase of clay content and decrease of water
volume supply had caused decrease of N, P and K leaching and increase of plant biomass production.
Interaction between clay content and volume of water supply insignificantly influenced plant height. The highest
biomass production was obtained on very fine clay content with level of water supply 100 % of water holding capacity. Among
the three nutrients in PHONSKA fertilizer, Nitrogen was the most easily leached and Phosphorous was the most resistant to
leaching.