Effects of biochars produced from different feedstocks on soil properties and sunflower growth

Abstract

The use of biochar as a soil amendment is gaining interest to mitigate climate change and improve soil fertility and crop productivity. However, studies to date show a great variability in the results depending on raw materials and pyrolysis conditions, soil characteristics, and plant species. In this study, we evaluated the effects of biochars produced from five agricultural and forestry wastes on the properties of an organic‐C‐poor, slightly acidic, and loamy sand soil and on sunflower (Helianthus annuus L.) growth. The addition of biochar, especially at high application rates, decreased soil bulk density and increased soil field capacity, which should impact positively on plant growth and water economy. Furthermore, biochar addition to soil increased dissolved organic C (wheat‐straw and olive‐tree‐pruning biochars), available P (wheat‐straw biochar), and seed germination, and decreased soil nitrate concentration in all cases. The effects of biochar addition on plant dry biomass were greatly dependent upon the biochar‐application rate and biochar type, mainly associated to its nutrient content due to the low fertility of the soil used. As a result, the addition of ash‐rich biochars (produced from wheat straw and olive‐tree pruning) increased total plant dry biomass. On the other hand, the addition of biochar increased the leaf biomass allocation and decreased the stem biomass allocation. Therefore, biochar can improve soil properties and increase crop production with a consequent benefit to agriculture. However, the use of biochar as an amendment to agricultural soils should take into account its high heterogeneity, particularly in terms of nutrient availability.

Characteristics and Potential Values of Bio-Products Derived from Switchgrass Grown in a Saline Soil Using a Fixed-Bed Slow Pyrolysis System

“…The pore structure changes in the switchgrass biochars were similar to those in other lignocellulosic biochars (Xiao et al 2014). The biochar produced at 500 °C had a greater number of smaller pores and a larger surface area, which might enhance its performance as soil amendment and improve soil fertility (Alburquerque et al 2014;Liu et al 2016). Moreover, the small pores in the biochar may be conducive to bacterial and fungal colonization, and protect plants from being preyed on by soil fauna, such as protozoa (Warnock et al 2007).…”

Effect of wheat and Miscanthus straw biochars on soil enzymatic activity, ecotoxicity, and plant yield

“…The authors reported no changes in soil pH after applying Miscanthus biochar in lower doses (30 and 60 t ha -1 ). Also Alburquerque et al (2013) found that the application of wheat straw biochar in doses below 1% (30 t ha -1 ) in slightly acidic soil did not affect its pH. They observed a significant increase in the soil pH to the value of 8.5 only after applying a 225 t ha -1 dose of wheat straw biochar.…”

“…They observed a significant increase in the soil pH to the value of 8.5 only after applying a 225 t ha -1 dose of wheat straw biochar. However, Alburquerque et al (2013) argued that the biochar applied by them in doses of over 30 t ha -1 had a negative effect on the crop yield due to significantly increased electrical conductivity. The doses of organic materials applied in this study did not significantly increase electrical conductivity (EC) compared to the parameter value determined in the MF treatment (Table 3).…”

“…Consumption of unstable nutrients by soil microorganisms affects numerous biological parameters of the soil, such as enzymatic activity (Kuzyakov et al, 2009;Mierzwa-Hersztek et al, 2016;Paz-Ferreiro et al, 2014), microbial biomass (Zavalloni et al, 2011), and diversity of microorganisms (Lehmann and Joseph, 2015). Ameloot et al (2015) and Alburquerque et al (2013) suggested that biochar is an excellent source of nitrogen available not only to microorganisms, but also to plants. This is mainly due to changes in the soil pH and C:N ratio, which play an important role in the stimulation of microorganisms involved in the mineralisation of organic matter and nitrogen transformations.…”

Biochar-compost mixture as amendment for improvement of polybag-growing media and oil palm seedlings at main nursery stage

“…This insignificant response on plant growth was probably associated with the insignificant improvement in nutrients uptake. The delayed effects of biochar on plant nutrients uptake (especially N, P and K) was likely due to temporary unavailability of nutrients for plant uptake (Lentz and Ippolito 2012) and N immobilisation when C:N ratio was above 16 (Alburquerque et al 2014;Walter and Rao 2015). The C:N ratio of EFB biochar was 93, and therefore, it potentially induced the immobilisation of mineral N. This was also supported by the observation in plant N, P, and K uptake, where the treatments with biochar showed no significant contribution in both 75 and 100% fertiliser rates.…”