RESUMO
The use of plant biostimulants, also known as bioeffectors (BEs), has attracted increasing attention as an environmentally friendly strategy for more sustainable crop production. BEs are substances or microorganisms that are applied to plants or the surrounding soil to stimulate natural processes to enhance nutrient uptake, stress tolerance, and plant growth. Here, we tested the effectiveness of five BEs to enhance maize growth and phosphorus (P) uptake from various recycled P fertilizers in a series of pot and field experiments. First, the impact of two bacterial BEs and one soil-specific plant-based BE on crop performance was assessed in a 4-week screening experiment conducted in two arable, P-deficient soils of differing soil pH (a silty clay loam of pH 7.1 and a silty loam of pH 7.8) amended with recycled P-fertilizers (rock phosphate, biogas digestate, green waste compost, composted dairy manure, and chicken manure pellets). Then, for each soil type, the plant growth-promoting effect of the most promising BE-fertilizer combinations was re-assessed in an 8-week experiment. In addition, over a period of up to 3 years, three field experiments were conducted with maize in which up to two bacterial BEs were used either alone or in combination with a plant-based BE. Our experiments show that while BEs in combination with specific P-fertilizers can promote maize growth within the first weeks of growth under controlled conditions, the observed effects vanished in the long term, both in pots and under field conditions. In a tracing experiment, in which we tested the persistence of one bacterial BE over a period of 5 weeks, we observed a drastic decrease in colony-forming units already 2 weeks after inoculation. As previously shown in other studies, our data indicate that the plant growth-promoting effects of BEs found under controlled conditions are not directly transferable to field conditions. It is suggested that the drastic decline in inoculated bacterial strains in the tracing experiment is the reason for the decline in plant growth effect.
RESUMO
OBJECTIVES: The subtalar screw arthroereisis (SSA) is a treatment option for painful pediatric flexible flatfeet (PFF). Hence, the optimal time point for a SSA is discussed controversially. Therefore the present study evaluates the influence of the patient's age at surgery on the radiological outcome to provide further evidence in this matter. METHODS: From 08/2007 to 12/2015 50 patients with 95 PFF were included. Inclusion criteria were: 1) Patients with PFF under or equal 15 years of age, 2) treatment with SSA and 3) presence of pre-op, post-op and follow up (FU) routine biplane radiographs. A subdivision was made into group A: 5-8 years, group B: 9-12 years and group C: 13-15 years. The radiographs were analyzed for: 1) calcaneal-pitch (CP), 2) lateral talocalcaneal angle (lat. TCA), 3) a.p. talocalcaneal angle (a.p. TCA, kite angle) and 4) navicular-cuboidal-index (NCI) and meary angle. RESULTS: Our study showed the best deformity correction when surgery was conducted between 9 and 12 years of age (group B), with significant improvement in all measured parameters without secondary deterioration during FU. In group A, the SSA show inferior results with poorer long-term success with only an improvement in the a.p. TCA. Group C showed mixed results. While CP and NCI improved, the lat. TCA deteriorated in FU. In conclusion, the ideal age for surgical intervention by SSA is between 9 and 12 years. Surgery before the age of 8 years did not show long-term success and delayed treatment at the age of 13-15 was only partially successful with deterioration during FU period. LEVEL OF EVIDENCE: IV.