Multi-Trait Wheat Rhizobacteria from Calcareous Soil with Biocontrol Activity Promote Plant Growth and Mitigate Salinity Stress

Plant growth promoting rhizobacteria (PGPR) can be functional microbial fertilizers and/or biological control agents, contributing to an eco-spirit and safe solution for chemical replacement. Therefore, we have isolated rhizospheric arylsulfatase (ARS)-producing bacteria, belonging to Pseudomonas and Bacillus genus, from durum wheat crop grown on calcareous soil. These isolates harbouring plant growth promoting (PGP) traits were further evaluated in vitro for additional PGP traits, including indole compounds production and biocontrol activity against phytopathogens, limiting the group of multi-trait strains to eight. The selected bacterial strains were further evaluated for PGP attributes associated with biofilm formation, compatibility, salt tolerance ability and effect on plant growth. In vitro studies demonstrated that the multi-trait isolates, Bacillus (1.SG.7, 5.SG.3) and Pseudomonas (2.SG.20, 2.C.19) strains, enhanced the lateral roots abundance and shoots biomass, mitigated salinity stress, suggesting the utility of beneficial ARS-producing bacteria as potential microbial fertilizers. Furthermore, in vitro studies demonstrated that compatible combinations of multi-trait isolates, Bacillus sp. 1.SG.7 in a mixture coupled with 5.SG.3, and 2.C.19 with 5.SG.3 belonging to Bacillus and Pseudomonas, respectively, may enhance plant growth as compared to single inoculants.

Microbial fertilizer from PK rocks on lettuce nutrients and soil attributes in consecutive crops

The objective of this work was to evaluate the effect of a microbial fertilizer, produced from phosphate and potassic rocks and earthworm compost, as an alternative to conventional fertilizers, on lettuce (Lactuca sativa) nutrients and soil attributes. The experiment was conducted in consecutive cycles (30 and 60 days) in a soil from the Lorca region, in the municipality of Murcia, Spain. The fertilization treatments were: conventional fertilizer, 100% of the recommended rate (RR); microbial fertilizer, 50% of the RR (5 Mg ha-1); microbial fertilizer, 100% of the RR (10 Mg ha-1); microbial fertilizer, 150% of the RR (15 Mg ha-1); and control, without N-P2O5-K2O fertilization. The microbial fertilizers applied at 100 and 150% of the RR showed significant and positive effects, as well as the best results for plant characteristics. The microbial fertilizer increased total N and available P and K compared with the conventional fertilizer. A residual effect was observed in the successive cycle. The effectiveness of the microbial fertilizer shows it is a viable alternative to conventional fertilizers, with positive effects on plant productivity and soil attributes.

Biochemical activity and bioassay on maize seedling of selected indigenous phosphate-solubilizing bacteria isolated from the acid soil ecosystem

Phosphorus availability is the major constraint for plant growth in the acid soil ecosystem, due to high fixation by Al and Fe. Microbial fertilizers such as phosphate-solubilizing bacteria (PSB) can increase P availability in soils for root uptake. The objective of the research was to verify the ability of four isolates of PSB isolated from acid soil to solubilize unavailable inorganic phosphate, produce phosphatase, malic acid and indole acetic acid (IAA), as well as increase plant height of maize seedling. The bioassay by growing maize seedling in liquid nutrients has been performed to study the response of seedling to PSB inoculation. The experimental design of bioassay was a randomized block design with five replications. The results showed that the isolates RR 1 and SPR 4 had a relatively high solubilizing index. Moreover, all the PSB isolates had the ability to produce phosphatase and IAA and dissolve P. The performance of PSB-inoculated seedling was better visually and the root length was increased by 66.7–74.5% compared to the control. This result concludes that the species of four isolates needs to be identified by a biomolecular method and formulated as biofertilizers for increasing the maize productivity in the acid soil ecosystem.

Effectiveness of maize foliar treatment by complex and microbial fertilizers

Оптимизация питания кукурузы, в том числе применение подкормок, является рычагом повышения её кормовой продуктивности. Целью исследований было выявление эффективности фолиарной обработки посевов кукурузы комплексными и микробиологическими препаратами при возделывании её на кормовые цели. Исследования по изучению эффективности фолиарной обработки посевов кукурузы проведены по общепринятой методике в СХПК им. Мичурина в Вавожском районе Удмуртской Республики. Полевые опыты закладывали на дерново-среднеподзолистой среднесуглинистой почве с повышенным содержанием гумуса (2,6–3,0%), с близкой к нейтральной и нейтральной обменной кислотностью (рН — 5,6–6,4), очень высоким (более 250 мг/кг) содержанием подвижного фосфора и калия. Схема опыта включала обработку комплексными удобрениями Agree`s «Аминовит», Agree`s «Азот», Agree`s «АзотКалий», Agree`s «Магний», Agree`s «Цинк» и их применение совместно с микробиологическими препаратами «Азотовит» и «Фосфатовит» с расходом рабочего раствора 200 л/га. В среднем за 2016–2018 годы фолиарная подкормка посевов кукурузы способствовала увеличению площади листовой поверхности в фазе вымётывания на 0,7–2,4 тыс. м2/га, в фазе цветения — на 0,3–3,2 тыс. м2/га, в фазе молочно-восковой спелости зерна — на 0,5–3,5 тыс. м2/га. Эффективность фолиарной обработки посевов кукурузы проявилась в увеличении площади листьев в течение вегетационного периода и повышении кормовой продуктивности, о чём свидетельствует прямая средняя и сильная корреляционная связь (r = 0,65–0,79) с урожайностью сухого вещества. В среднем за 3 года исследований наибольший эффект получен от фолиарной обработки посевов в виде повышения сбора сухого вещества на 1,4–4,9 т/га. Совместное применение микробиологических удобрений «Азотовит» и «Фосфатовит» с комплексными удобрениями Agree`s «Азот» или Agree`s «АзотКалий» обусловило формирование наибольшей продуктивности — 16,3–16,7 т/га. Optimal maize nutrition, including topdressing, is a key to increase crop productivity. The research focused on the effect of foliar treatment by complex and microbial fertilizers on maize performance. Experiments were carried out in accordance with the standard methods at the Agricultural Production Cooperative n. a. Michurin. Sod-podzolic soil had medium clay content and was rich in soluble phosphorus and potassium (over 250 mg/kg), humus concentration — 2.6–3.0%, рН — 5.6–6.4. Complex fertilizers (Agree`s “Aminovit”, Agree`s “Azot”, Agree`s “AzotKaliy”, Agree`s “Magniy”, Agree`s “Tsink”) were applied together with the “Azotovit” and “Fosfatovit” microbial preparations at the rate of 200 l h-1. Maize topdressing increased leaf area by 0.7–2.4 thousand m2 ha-1 at the ear formation stage, 0.3–3.2 thousand m2 ha-1 — at the flowering stage, 0.5–3.5 thousand m2 ha-1 — at the milk-wax stage for 2016–2018. Foliar feeding led to the increase in leaf area and productivity during a growing season positively affecting dry matter (DM) yield (r = 0.65–0.79). Foliar fertilization resulted in DM increase of 1.4–4.9 t ha-1 for 3 years. Combination of “Azotovit” and “Fosfatovit” with Agree`s “Azot” or Agree`s “AzotKaliy” provided the highest productivity — 16.3–16.7 t ha-1.

Modulation of insect-induced oxidative stress responses by microbial fertilizers in Brassica juncea

ABSTRACT Microbial fertilizers have increasingly gained popularity as environmentally sustainable nutritional supplement for plant growth. However, the effect of these microbes on plant-induced responses and the resultant effect on late-arriving herbivores are still unclear. Following insect herbivory, oxidative stress is one of the earliest responses induced in plants. Therefore, we analyzed the effect of phosphorus solubilizing bacteria (PSB), vesicular-arbuscular mycorrhiza (VAM) and their combination on oxidative stress in Brassica juncea against Spodoptera litura herbivory. Six antioxidant enzymes, viz. superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), monodehydroascorbate reductase and glutathione reductase (GR), were studied. Our results indicated a sporadic increase of APX and GR in PSB-supplemented plants. In contrast, VAM-supplemented plants showed an active systemic response against herbivory with an increase in all the six enzymes at 72 h. Conversely, supplementation of PSB–VAM together led to increased APX, SOD, CAT and POD enzymes, which subsided by 72 h. Thus, the presence of VAM, alone or in combination with PSB, acted like a vaccination for plants against stress. However, the mode of action of PSB and VAM governed the temporal dynamics of antioxidants. Our study thus shows microbial fertilizers have prominent effects on plant immunity.

Beetroot and radish root yield in organic double-cropping production system

Despite numerous positive effects on the environment, increased demands, intense research, and adequate public attention, crops grown according to the principles of organic production still occupy considerably small areas. It is difficult for certified producers to decide to expand the production of certified organic vegetables. One of the reasons is the insufficiently developed growing technology of different vegetable species in accordance with the law and regulations on organic production. Intercropping, growing of subsequent crops, and application of microbiological fertilizers are considered as the most useful techniques for yield increases in sustainable growing practices. The aim of this study was to investigate the possibilities for enhancing root yield of beetroot and radish, when grown as second crops in an organic double-cropping production system. The effects of intercropping and applying microbial fertilizers on the vegetable root weights were assessed. Intercropping was with green beans, implemented by replacement series method. Two microbial fertilizers were applied, one containing selected strains of Bacillus megatherium, B. licheniformis, B. suptilis, Azotobacter chrocoocum, A. vinelandi and Derxia sp. (M1), and other with Bacillus subtilis, Azotobacter sp., Penicillium oxalicum and Fusarium sp. (M2). Intercropping and microbial fertilizers contributed to the root weight increase. The highest root weights were noted for the intercropped plants treated with M1 (beetroot, 151.8 g) and M2 (radish, 351.0 g), which was 23.5% and 15.5% higher than in the sole crop unfertilized control. The results imply combining intercropping and the appropriate microbial fertilizers as an effective strategy for increasing yields of organically grown beetroot and radish.