Azolla fertilizer as an alternative N source for red spinach production on alluvial and peat soils in West Kalimantan, Indonesia

Dwi P. Widiastuti1, Jessica G. Davis1, Sutarman Gafur2

1 Colorado State University, Dept. of Soil & Crop Sciences, Colorado State University, Fort Collins, CO, USA, 80523-1170, http://soilcrop.agsci.colostate.edu/, [email protected]

2 Tanjungpura University, Jl. Prof. Dr. H. Hadari Nawawi, Pontianak, West Kalimantan, Indonesia, 78124

Abstract

Food security is an important goal in Indonesia, and each household is expected to utilize their backyard to provide food (vegetables) for their family. One approach to intensify vegetable production is through locally-grown fertilizer. Through biological nitrogen fixation, the Azolla-Anabaena symbiosis can provide N for vegetable production. The objective of this study was to evaluate the contributions and Nitrogen Use Efficiency (NUE) of A. pinnata as a biofertilizer on red spinach production on Inceptisols and Histosols in West Kalimantan, Indonesia compared to commonly-used fertilizers. The experimental design was a Randomized Complete Block Design with three replications. Five N fertilizer treatments were used: control, urea at 50 kg ha-1, chicken manure at 5 t ha-1, Azolla at the urea N rate, and Azolla at the manure N rate. Treatment means were compared using the honestly significant difference Tukey adjusted post hoc test (n=3, P<0.1). Overall, the results showed that Manure had the highest yield in the alluvial soil and it was comparable to Urea; whereas, in the peat soil, the significantly highest yield was also from the Manure treatment, but it was comparable to Azolla applied at the manure N rate. The highest leaf N content was in the Manure treatment (in the alluvial soil) and the Azolla applied at the manure N rate (in the peat soil). The highest NUE was in the Urea treatment in the alluvial soil. Therefore, Azolla applied at the manure N rate can be used as an alternative biofertilizer, especially for peat soil.