Influence of Various Composted Organic Amendments and Their Rates of Application on Nitrogen Mineralization and Soil Productivity Using Chinese Cabbage (Brassica rapa. L. var. Chinensis) as an Indicator Crop

Charlie Suruban,Md Abdul Kader,Zakaria M Solaiman

doi:10.3390/agriculture12020201

Charlie Suruban, Md Abdul Kader + Show 1 more

Open Access

https://doi.org/10.3390/agriculture12020201

Copy DOI

Abstract

There is a diversity of locally available nitrogen (N)-rich organic materials in Samoa. However, none of them was evaluated for their N supplying capacity after composting in Samoan Inceptisols for vegetable cultivation. Thus, N-releasing capacity of five composted organic amendments (OAs) namely macuna, gliricidia, erythrina, lawn grass and giant taro, and their two application rates (10 and 20 t ha−1) were assessed through a laboratory incubation and a crop response study using Chinese cabbage as a test crop. Among the OAs, composted mucuna was characterized by a higher total N (2.91%), organic C (63.6%) and NO3−N content (341 mg N kg−1). A significant difference in N mineralization was observed among the OAs as well as application rates. The highest N mineralization was recorded in composted mucuna followed by gliricidia, erythrina, lawn grass, and giant taro. A crop response study also showed a similar trend. Mucuna treatment had the highest biomass yield and N uptake followed by gliricidia, erythrina, lawn grass, and giant taro. Leguminous composted OAs @ 20 t ha−1 performed substantially better in all the plant growth and yield parameters, and N uptake compared to 10 t ha−1 that was not the case for non-leguminous OAs. Thus, non-leguminous OAs should be applied at 10 t ha−1. All the composted leguminous OAs showed promising results while mucuna was the best in both the application rates. Therefore, mucuna can be promoted to supply N for crop cultivation in Samoa, other Pacific Islands and tropical countries where N fertilizer is costly and not easily available.

Highlights

In South Pacific Island countries (SPIc), including Samoa, most farmers follow the traditional shifting cultivation system and are not applying fertilizer [1]
The incubation experiment was conducted in the laboratory, whilst the pot experiment was conducted in the screen house at the Alafua Campus, University of South Pacific (USP), Samoa, from May to October 2017
The highest amount of total N was found in mucuna compost followed by erythrina, glirichida, lawn grasses, and giant taro compost

Summary

Introduction

In South Pacific Island countries (SPIc), including Samoa, most farmers follow the traditional shifting cultivation system and are not applying fertilizer [1] This is because chemical fertilizers are very costly for being imported from abroad and transportation costs are much higher due to the remoteness and isolation of these island countries. Considering the traditional farming system and high cost of imported chemical fertilizers, organic sources of nutrients are the best alternatives to inorganic fertilizers for sustainable soil management and agricultural development in SPIc’s [2]. Some of the SPIc’s governments, including Samoa, initiated programs to promote the application of organic fertilizer With such awareness throughout the initiative programs of the Samoan government, farmers have been showing greater interest in following organic practices in crop production. One of the problems identified for crop N nutrition management prompted farmers to use costly inorganic fertilizers

Objectives

Methods

Results

Conclusion