Soil Biochar Application: Assessment of the Effects on Soil Water Properties, Plant Physiological Status, and Yield of Super-Intensive Olive Groves under Controlled Irrigation Conditions

Abstract

The effects of olive waste biochar and green compost as soil amendments on soil physical properties, as well as on physiological parameters and yield of a super-intensive olive crop cultivated under deficit irrigation conditions, were investigated in south-west Spain during the 2021 growing season. Thus, soils were amended with 40 t ha−1 of olive pomace waste biochar, green-compost, or a biochar-compost mixture (50% w/w), and no amended plots were used as control. On a bi-monthly basis, soil pH, water holding capacity, humidity, and resistance to penetrability were determined. In addition, various indicators of the physiological status and water stress of the plant were also monitored. Finally, the olive yield per tree was measured. Results showed that biochar application was the most effective amendment for increasing soil moisture and reducing soil compaction. The latter was evidenced by the significant reduction of the resistance to the penetrability of the amended soils. Plants of the amended plots showed better leaf water potential. In addition, values of the net photosynthesis rate, the average intrinsic water-use efficiency, and the maximum rate of electron transport in the time before the harvest improved significantly in the trees from the biochar-amended plots, for which olive fruit yields increased by about 15% in comparison with the other treatments. Nevertheless, the estimated net oil yield per tree was similar because the olives from the biochar-amended trees contained more moisture. This field trial shows for the first time that by providing the soil with biochar from olive crop waste as an organic amendment, having high water retention capacity, porosity, and stability, it would be possible to reduce the irrigation water needed and maintain plant yields.

Effects of Different Water Storage and Fertilizer Retention Substrates on Growth, Yield and Quality of Strawberry

“…Research has shown that increasing the organic matter content by means of composting also increases the water retention of the substrate [33]. Applying coconut bran and biochar to organic fertilizers can improve the soil's physicochemical properties and stimulate crop root growth and development [34][35][36]. Incorporating vermicompost and coconut bran increased the organic matter, alkaline dissolved nitrogen, quick-acting potassium and effective phosphorus contents of the substrate, which is similar to the findings by Bellitürk K et al [37].…”

Biochars Derived from Olive Mill Byproducts: Typology, Characterization, and Eco-Efficient Application in Agriculture—A Systematic Review

“…After applying OP biochars, even more pronounced impacts in soil EC were recorded [38,42,51,55,67]. Hmid et al [67] reported that the OP biochar application with 15% in sandy soil increased the EC from 0.06 dS m −1 to 0.19 dS m −1 , making it unlikely that amended soils have a detrimental effect on microbial activity and crop growth [117].…”

“…Hormesis is regularly detected, meaning that high biochar rates can harm plants, while low rates can be stimulatory. Both positive [39,40,46,47,51,55,68,72,79,81] and negative [33,42,57,59,60,74] responses have been found in field trials to enhance yield crop as a result of biochar application to soils (Table 6).…”

“…In this regard, Hmid et al [68] observed that increasing OP biochar increased 15-day-old bean growth and soluble protein contents and decreased the activities of antioxidant enzymes and leaf Cd, Pb, and Zn contents. Besides, De la Rosa et al [51] found that olive trees amended with OP biochar had better water and photosynthetic conditions.…”

Aromaticity, polarity, and longevity of biochar derived from disposable bamboo chopsticks waste for environmental application

“…However, using biochar for various purposes depends on the biochar properties, including morphology, physical properties, and physicochemical properties [ [21] , [22] , [23] ]. One of the primary uses of biochar is as a soil amendment; such applications must take into account biochar pH, cation exchange capacity, and porosity [ 24 , 25 ].…”