Tropentag 2023, September 20 - 22, Berlin, Germany "Competing pathways for equitable food systems transformation: trade-offs and synergies."

Azolla compost as an alternative source of nitrogen for organic vegetable cultivation

Vietnam National University of Agriculture (VNUA), Dept. of Cultivation Sciences, Vietnam

Abstract

The spread of organic farming in Asia has led to the need to find alternative sources of high quality organic fertiliser. Azolla is a genus of floating water ferns that is high in nitrogen and organic matter due to its rapid growth and symbiotic relationship with nitrogen-fixing bacteria (Anabeana azollae). It is grown as a green manure in rice fields in many Asian countries. However, little research has been done on the use of Azolla as an organic fertiliser for vegetable production. The objective of this study was to evaluate the effects of different levels of Azolla compost fertiliser on the growth and yield of Malabar spinach (Basella alba) - a popular vegetable crop in the tropics and subtropics - to improve the process of using Azolla as an organic fertiliser in vegetable production. The experiment included 6 treatments: Without application-as control (T1); 1 t ha^-1 soybean meal (T2); 16 t ha^-1 cow manure (T3); 12 t ha^-1 Azolla fertiliser (T4); 16 t ha^-1 Azolla fertiliser (T5); and 20 t ha^-1 Azolla fertiliser (T6). Our results showed that Azolla fertiliser application significantly increased shoot length, number of leaves, leaf size, dry matter, leaf area index (LAI) and SPAD of Malabar spinach compared to control or cow manure. Application of Azolla fertiliser at rates of 12, 16, and 20 t^-1 ha significantly increased the yield of Malabar spinach by 150, 192, and 205%, respectively, compared to the control and by 37, 60, and 67%, respectively, compared to the cow manure treatment. Our results suggest that Azolla fertiliser can be used as an alternative organic nitrogen source in organic vegetable production. However, genotype selection and rapid multiplication of Azolla are necessary to develop it as a nitrogen source that meets the requirements of fast-growing organic agriculture.

Keywords: Azolla fertiliser, Basella alba, manure, organic vegetable

Contact Address: Duy Hoang Vu, Vietnam National University of Agriculture (VNUA), Dept. of Cultivation Sciences, Ngo Xuan Quang - Gialam, 131000 Hanoi, Vietnam, e-mail: vdhoang87gmail.com