Thesis Title "Effect of biochar produced from organic wastes on Lolium perenne L. και Zea Mays L"

Friday 6 July 2018, 10:00, Hall: Κ2.Α3

Supervisor: Evan Diamadopoulos

Seven-membered Examination Committee:

1 Evan Diamadopoulos, Professor - TUC

2 Danae Venieri,  Assistant Professor - TUC

3 Nikolaos Moustakas, Professor - Agricultural University of Athens

4 Nikolaos Nikolaidis, Professor - TUC

5 Konstantinos Komnitsas, Professor - TUC

6 Nikolaos Paranychianakis, Assistant Professor - TUC

7 Dr. Georgios Psarras, Researcher - Institute of Olive Tree, Subtropical plants and Viticulture, Chania

Abstract:

n the current PhD study, biochars derived from four different agricultural organic byproducts were assessed in plant cultivation. The organic by-products came from agro-industrial activities and were: grape pomace (GP), rice husks (RH), brewery spent grains (BSG) and brewery surplus yeast (BSY). Rice husks were chosen due to their great abundance worldwide, while the grape pomace due to the large quantities produced by the winemaking process in Crete. Brewery spent grain and surplus yeast were chosen due to the increase in brewing activity in Greece, hence the production of brewery by-products.

In the first part of the study, the effect of biochars produced at 300°C pyrolysis temperature and derived from rice husks (BC-RH) and grape pomace (BC-GP), was investigated on Lolium perenne L. A three-month period of ryegrass (Lolium perenne L.) cultivation was studied on two Mediterranean agricultural soils (Sandy loam-SL and Loam-L). The objectives of this study aim to ascertain (a) whether biochar, with or without compost, at an application rate of 2% (w/w), having received all nutrients but P (FNoP) or no fertilization at all (ΝοF), affect dry matter yield, P concentration and uptake in ryegrass shoot tissues and (ii) the impact of biochars with or without compost, at an application rate of 2% (w/w), having received no fertilization at all (ΝοF), on the nutrient status of ryegrass shoot tissues. According to the results, application of both types of biochar with or without compost, in the presence of inorganic fertilization except P, significantly increased dry matter yield of ryegrass (59-78%), compared to control, in SL soil, particularly, BC-FR (3.17 g/pot), compared to the control (1.78 g/pot), although no statistically significant increase was observed in L soil. No statistically significant differences were observed among the no fertilization treatments (NoF) in all three harvests for both soils. The addition of BC-GP and BC-GP+compost significantly increased the shoot P-concentration only in L soil, in all harvests, either in the presence or absence of inorganic fertilization except P. The application of BC-GP and BC-GP+compost resulted in increased shoot K concentration mainly in SL soil, while the treatment of BC-GP in L soil. Shoot Fe concentration increased by the addition of BC-RH+compost in SL soil, whereas Mn and Zn concentrations were significantly affected by the addition of compost and BC-GP+compost in both soils.

The second part of the study looked into the influence of biochar, compost and mixtures of the two on maize (Zea mays L.) yield, morphological traits and nutrient status of plant tissues and soils. Biochars were produced from 2 feedstocks: grape pomace (GP) and rice husks (RH) pyrolyzed at 300°C. Maize was grown for 30 days after seedling emergence in a greenhouse pot trial in two Mediterranean soils (Sandy Loam-SL and Loam-L) amended with biochar with or without compost at application rate of 2% (w/w) and N fertilization. The addition of BC-GP amendment resulted in the highest increase (155%) of aboveground dry weight compared to the control in SL soil, whereas in L soil the highest increase of aboveground dry weight resulted from BC-RH+compost (436%). The addition of BC-GP+compost significantly increased P concentration of the aboveground and belowground tissues only in L soil. K concentration of aboveground and belowground tissues significantly increased almost by all the amendments with the greatest increase observed by the addition of BC-GP+compost in SL soil, while K concentration significantly increased only in belowground tissues with the highest increase by the BC-GP application in L soil. Ca concentration significantly increased mainly in the belowground tissues in the L soil, while Mg concentration of belowground tissues was positively affected by the BC-GP and BC-GP+compost treatment in L and SL soil, respectively. The addition of BC-GP+compost significantly increased aboveground Fe concentration in both soils. The Mn concentration of aboveground and belowground tissues significantly increased by the BC-GP+compost treatment only in the SL soil. Zn belowground concentration was positively influenced by the treatments containing compost in the SL soil.

In the last part of the thesis, the effect of biochar derived from brewery spent grains (BSG) and brewery surplus yeast (BSY) was studied, having received N fertilization (F) or no N fertilization at all (NoF), on Zea Mays L. in a Loam (L) soil. The biochars were produced at 300°C pyrolysis temperature, while the total biochar application rate was either 2% (w/w) (BC-BSG-2%; BC-BSY-2%) or 5% (w/w) (BC-BSG-5%; BC-BSY-5%) for each type of biochar, as well as a mixture of both types (BC-BSG+BSY-1%+1%; BC-BSG+BSY-2.5%+2.5%). The influence of biochars on the dry weight and morphological characteristics of the plant, the concentrations of macronutrients and micronutrients of aboveground and belowground plant tissues, and the soil properties, including nutrients and pH, in an experiment 30 days after the seedling emergence were studied. The results showed that the addition of biochars significantly increased the aboveground dry weight of corn (46-157%), compared to the control, having received N fertilization, while by 59-186% without fertilization at all. Biochars individually or in a mixture at 5% application rate gave the highest increase of aboveground corn tissues. P concentration of tissues was significantly enhanced by biochars individually or in a mixture, especially by BC-BSY-5%, having received N fertilization or not. K concentration of aboveground tissues significantly increased by the addition of BC-BSY (BC-BSY-2% and BC-BSY-5%) at both application rates, and by the mixture at 5% application rate, without N fertilization. Ca belowground concentration was positively affected by BC-BSG-2% without N fertilization. Mg aboveground concentration was significantly increased by BC-BSG-5% and BC-BSG+BSY-2.5%+2.5% applications, without fertilization.

In conclusion, biochar addition could enhance plant yield, although soil conditions, type of biochar, application rate and additional fertilization should receive special attention in order for biochar to be an effective tool for the management of agricultural residues and sustainable agriculture.