Establishment and verification of prediction models for evaluating the physical and chemical properties of soilless substrates

Bo Gong ,Hongbo Gao,Tiejun Zhang,Guiyun Lyu,Ning Wang,Jingrui Li,Shao Li,Xiaolei Wu ,Jie Tian

doi:10.25165/j.ijabe.20211402.5815

Abstract

In soilless culture, a suitable mixed substrate that provides a balanced and stable rhizosphere environment is vital for promoting plant growth. The present study was undertaken to establish seven prediction models of physical and chemical properties, including bulk density (DB), total porosity (TP), water-holding porosity (WHP), air porosity (AP), WHP/AP, electrical conductivity (EC) and cation exchange capacity (CEC) of mixed substrate based on regression equations of measured values from 76 substrate combinations. These seven models were verified using the measured values of 12 mixed substrates, and the average relative prediction errors (REs) were all less than 10%. A comprehensive property prediction model was established by weighted summation of the seven models of physical and chemical properties. According to the set values of DB, TP, WHP, AP, WHP/AP, EC and CEC, the comprehensive property model predicted the six mixture proportions of mixed-substrate, as verified using the measured values. This study is the first to establish prediction models for the physical and chemical properties of mixed substrates. The comprehensive property model could be used to evaluate the physical and chemical properties of commercial mixed substrates, and to provide the optimal mixture substrate formulations according to the setting property value of production requirement. Keywords: prediction model, mixed substrate, physical and chemical properties, multiple regressions, genetic algorithm DOI: 10.25165/j.ijabe.20211402.5815 Citation: Gong B B, Wang N, Zhang T J, Li S, Wu X L, Tian J, et al. Establishment and verification of prediction models for evaluating the physical and chemical properties of soilless substrates. Int J Agric & Biol Eng, 2021; 14(2): 9–18.

Highlights

Soilless plant culture is a cultivation method that does not use soil to support the plant growth, among which mainly involves containerization of plant roots within porous rooting medium known as ‘substrate’ or ‘growing media’[1]
The values of DB, total porosity (TP), water-holding porosity (WHP), air porosity (AP), WHP/AP, electrical conductivity (EC) and cation exchange capacity (CEC) significantly differed among the 76 formulations containing 5 substrates in different proportions (Table 3)
Across the formulations, the values of DB ranged between 0.12 and 0.46 g/cm3, the values of TP ranged between 56.82% and 82.05%, the values of WHP ranged from 38.93% to 71.14%, the values of AP ranged from 4.61% to 24.51%, the values of EC ranged from 0.02 to 1.65 mS/cm and the values of CEC ranged from 10 to 61.25 cmol/kg

Summary

Introduction

Soilless plant culture is a cultivation method that does not use soil to support the plant growth, among which mainly involves containerization of plant roots within porous rooting medium known as ‘substrate’ or ‘growing media’[1]. According to a recent investigation on substrate utilization in China, the demand for solid substrate annually is approximately 50 million m3, including 15 million m3 for vegetables, 10 million m3 for landscaping, 8 million m3 for rice seedlings, 8 million m3 for soilless cultivation and 9 million m3 for soil restoration[8]. During the substrate mixed process, the formulation of different substrate proportion should be adjusted according to the characteristics of used single substrate and different crops to meet the needs of plant growth for the root environment[10]. There is currently no standardized method to evaluate whether the properties of the mixed substrate can meet the needs of plants, and the design of the substrate mixed formulation is mainly based on limited data from proportional experiments or farmer’s experience[2,11]

Methods

Results

Discussion

Conclusion