Effect of biochar amendment on morphology, productivity and water relations of sunflower plants under non-irrigation conditions

Abstract

Three biochars (B1: pine wood, B2: paper-sludge, B3: sewage-sludge) produced under controlled pyrolysis conditions and one produced in kilns (B4: grapevine wood) were used as organic ameliorants in a Calcic Cambisol, which represents a typical agricultural soil of the Mediterranean region. This field study was performed with plants of sunflower (Helianthus annuus L.) at the experimental station "La Hampa", located in the Guadalquivir river valley (SW Spain). The soil was amended with doses equivalent to 1.5 and 15 t ha −1 of the four biochars in two independent plantations. In addition, un-amended plots were prepared in both experiments for comparison purposes. The major goal of this study was the assessment of the effect of biochar amendment on the physiology and development of sunflower plants at field conditions. During most of the growing period plants of un-amended and amended plots showed no stress symptoms either by their appearance or by stress-sensitive biochemical parameters such as the stability of the photosystem II (QY). Biochar addition had no effect on seed germination. Addition of 1.5 t ha −1 biochar did not significantly change the pH of the soil, its electrical conductivity (EC) or its water holding capacity (WHC). Concomitantly the plant development and plant biomass production remained unaltered. Amendments with 15 t ha −1 slightly increased the WHC of the soil but showed no lasting impact on the soil pH. It stimulated plant growth and led to a greater leaf area, larger plant stems and wider inflorescences of the sunflower plants than those cultivated on the un-amended soil. At the end of the experiment, biochar amendment of soil caused no significant increase of the total biomass production excepting B4, the biochar with the lowest capacity of water retention, which exhibited the highest vegetative growth and seed production. The lack of rain during the last weeks caused a water shortage in the culture that produced greater QY loss in non-amended plants. Interestingly, better growth of amended plants during the drought period correlated with higher reduction of stomatal conductance, indicating that the greater water use efficiency is at the origin of the better crop performance of biochar-amended plants. This finding points to the agronomic relevance of biochar amendment of Mediterranean rain fed crops.

Does soil aging affect the N2O mitigation potential of biochar? A combined microcosm and field study

“…Considering the more specific characteristics for the field trial in the present study according to the classifications of Jeffery et al (2015) (biochar application rate of 51-60 t ha À1 ,~19% yield increase; wood biochar,~28% yield increase; initial pH of soil in the range of 7.1-7.5,~20% yield increase but not significant at the 5% level), a yield increase could have been expected. However, Paneque et al (2016) observed an increase in sunflower yield after application only with one of four biochars tested in a Mediterranean soil.…”

“…However, Paneque et al . () observed an increase in sunflower yield after application only with one of four biochars tested in a Mediterranean soil.…”

Biochar and Soil Physical Properties

“…Table 8 also shows two trends. First, although various studies report increased water retention even at low rates of biochar application, two studies found that biochar only increased water retention when the amount applied was ³15 Mg ha -1 (Paneque et al, 2016;Xiao et al, 2016). This suggests that large amounts of biochar can be required to increase water retention consistently.…”

Potential of Integrating Biochar and Deficit Irrigation Strategies for Sustaining Vegetable Production in Water-limited Regions: A Review

“…The alterations in the water-holding capacity of soil have been widely studied (Paneque et al, 2016;Zhang et al, 2016). The application of biochar has shown a consistent increase in the water retention ability of soils, although the results are more noticeable in coarse-textured soils compared with fine-textured clay soils (Blanco-Canqui, 2017).…”