Addition of biochar to acidic boreal podzolic soils enhances micronutrient availability and crop productivity

Joinal Abedin,Adrian Unc

doi:10.1515/opag-2020-0021

Abstract

Abstract Results of a recent multiyear experiment conducted on an agricultural plot that was recently converted from boreal forest (Labrador, Canada) suggested that NPK fertilizers contributed to better crop establishment and higher yield but only when it was applied along with biochar. The failure of fertilizer only treatments to allow crop establishment and desirable growth and yield could be related to the deficiency of one or more micronutrients. Consequently, a missing element trial with a number of micronutrients (Mn, Cu, Zn, and Mo) was initiated on the same soil to investigate whether biochar can facilitate the availability of one or more of these micronutrients, contributing to crop growth and yields. Results show that the incorporation of chemical fertilizers with biochar produced significantly higher yields than in the absence of biochar. Furthermore, in the absence of biochar, the addition of micronutrients (i.e., Mn, Cu, Zn, and Mo) did not significantly increase yield. On the other hand, among the treatments that included biochar, the absence of a micronutrient (i.e., only three of the four micronutrients included) had either no effect (e.g., absence of Mn or Zn) or was associated with the increased yields (i.e., absence of Cu or Mo). Thus, it is proposed that while all tested micronutrients were present in the podzolic soil, with Cu and Mo possibly oversupplied, co-application with biochar enhanced both macronutrient and micronutrient utilization by plants. The data on the availability of micronutrients in the soil, their concentration in plants, and total uptake also support this conclusion. Thus, biochar facilitates the plant uptake of both naturally occurring and added micronutrients, and associated crop productivity, in a podzolic soil typical for lands converted from forest to agricultural use in the boreal ecoregion of Labrador. These results also challenge the view that micronutrients must always be added to Podzols to achieve maximum productivity; biochar-mediated micronutrient plant uptake deserves consideration when managing Podzols.

Highlights

To increase local food security, there is no sustainable alternative other than producing more affordable and quality foods locally
The soil organic matter (SOM) content was not related to the biochar application (Table 2), but increased in time (Figure 1)
The exclusion of Cu or Mo from the micronutrient amendment mix led to the improved yields, an indication of the capacity of biochar to mobilize the naturally occurring stores of these elements and leading to possible excess in the Cu- and Mo-amended plots

Summary

Introduction

To increase local food security, there is no sustainable alternative other than producing more affordable and quality foods locally. The Government of Newfoundland and Labrador (NL) decided to boost food security by implementing policies that support expansion of farmlands on Crown lands (Government of Newfoundland and Labrador 2017). This implies the conversion of boreal forests into agricultural lands. The primary soil type in the boreal forest is Podzol (Sanborn et al 2011; Walker 2012), a soil with many physical and chemical limitations that lead to its low fertility. The principal issues with the converted Podzols are low soil organic matter (SOM), acidic pH, and sandy soil texture (St Croix 2002). The stores and the availability of essential plant nutrients, which are commonly associated with clay, SOM, and neutral pH, are very low (Curtin and Rostad 1997)

Methods

Results

Discussion

Conclusion