Search

Carbon farming practices are pivotal for enhancing soil organic carbon (SOC) storage in agricultural systems. This study focuses on evaluating the effects of spontaneous cover crops as a conservation strategy compared to conventional management practices on total, non-protected, and protected SOC fractions, as well as carbon saturation, in olive groves across 13 paired sites (26 sites in total) in Andalucía, Spain. The research evaluates organic carbon concentrations in different soil fractions: non-protected (250–2000 µm), physically protected (53–250 µm), and chemically protected (<53 µm). The results reveal that olive groves managed with temporary spontaneous cover crops (CC) over the last 8–12 years generally exhibit higher SOC concentrations compared to those managed conventionally (BS), with significant differences observed across multiple sites. CC sites exhibited higher carbon stocks, with protected carbon averaging 42.6 Mg C ha−1 compared to 29.7 Mg C ha−1 in BS, and non-protected carbon at 10.3 Mg C ha−1 versus 4.8 Mg C ha−1. A direct relationship was identified between total SOC and both protected and non-protected carbon fractions, indicating that the soil of the studies olive orchards is far from being saturated in protected SOC. Moreover, the soil of the CC olive farms had a lower carbon saturation deficit (45.3%) compared to BS (67.2%). The findings show that maintaining the cover crops in olive orchards significantly contributed to carbon sequestration and reduced carbon saturation deficits by increasing the stocks of protected SOC. [ABSTRACT FROM AUTHOR]

Summary: Phosphate‐solubilising microorganisms (PSM) are often reported to have positive effects on crop productivity through enhanced phosphorus (P) nutrition. Our aim was to evaluate the validity of this concept. Most studies that report 'positive effects' of PSM on plant growth have been conducted under controlled conditions, whereas field experiments more frequently fail to demonstrate a positive response. Many studies have indicated that the mechanisms seen in vitro do not translate into improved crop P nutrition in complex soil–plant systems. Furthermore, associated mechanisms are often not rigorously assessed. We suggest that PSM do not mobilise sufficient P to change the crops' nutritional environment under field conditions. The current concept, in which PSM solubilise P 'for the plant' should thus be revised. Although PSM have the capacity to solubilise P to meet their own needs, it is the turnover of the microbial biomass that subsequently provides P to plants over a longer time. Therefore, the existing concept of PSM function is unlikely to deliver a reliable strategy for increasing crop P nutrition. A further mechanistic understanding is needed to determine how P mobilisation by PSM as a component of the whole soil community can be manipulated to become more effective for plant P nutrition. [ABSTRACT FROM AUTHOR]

Maize is becoming an increasingly important crop in northern Europe, but low temperatures during spring may hamper its growth. This effect may be caused by direct plant damage through oxidative stress or indirect damage through decreased uptake of nutrients, especially phosphorus (P), from the soil. Previous studies have indicated that treatment with micronutrients such as manganese and zinc (Mn/Zn), microbial inoculants (biostimulants) or exogenous salicylic acid can alleviate abiotic stress. Seed inoculation with microorganisms can also increase P uptake from the soil. In a pot experiment, we investigated whether the negative effects of cold stress could be alleviated by improving soil fertility (P level), inoculating seed with two different plant growth‐promoting fungi of the genus Penicillium sp., adding extra Mn/Zn at sowing or adding exogenous salicylic acid. These treatments were tested on maize plants subjected to cold stress and two different levels of soil fertility and harvested 28 and 51 days after sowing (DAS). We found that the effect of cold stress was not alleviated by improving soil fertility through the use of a more fertile (high P) soil or through fertilisation with plant‐available P in the form of triple superphosphate. Cold stress was also not alleviated by the treatment of seeds with salicylic acid. Addition of Mn/Zn and inoculation with one of the two Penicillium strains tested increased biomass production at 51 DAS (compared with the untreated control) in cold‐stressed plants grown in the high P soil, but not in the low P soil. Thus, addition of Mn/Zn and inoculation with Penicillium sp. can reduce the effects of cold stress in maize plants grown in fertile soil. [ABSTRACT FROM AUTHOR]