Associative interplay of plant growth promoting rhizobacteria (Pseudomonas aeruginosa QS40) with nitrogen fertilizers improves sunflower (Helianthus annuus L.) productivity and fertility of aridisol

The environmental and economic impacts of chemical fertilizer have encouraged farmers to integrate them with organic materials, an important nutrient management strategy for sustainable agriculture production. In the present study, we conducted field experiments to study the effects of nitrogen enriched compost (NEC) and mineral nitrogen (MN) fertilizer with a selected plant growth promoting rhizobacterial (PGPR) strain, Pseudomonas aeruginosa QS40, on productivity of sunflower and soil fertility. The results demonstrated that integrated application of PGPR with organic-inorganic N significantly increased shoot and root length, leaf area, total chlorophyll, head diameter, fresh biomass, straw-achene yield and N uptake in sunflower compared to unamended control and PGPR alone. The results also showed that integrated N biofertilizer regime enhanced soil microbial biomass, enzymatic activities and soil nitrogen contents. We also observed significant changes in rhizosphere soil pH, abundance of cultivable bacteria and arbuscular mycorrhizae fungi (AMF) root colonization. Treatment and year interaction was significant for dissolved organic carbon (DOC) and microbial biomass carbon (MBC) only. These results suggest that the efficiency of PGPR could be improved with increased availability of labile C substrate resource in NEC amended aridisol. We conclude that the application of NEC fertilizer with efficient PGPR biofertilizer may improve sunflower productivity and soil chemical and biological fertility in nutrient-poor agroecosystems of arid and semi-arid regions. (C) 2016 Elsevier B.V. All rights reserved.

Nitrogen-enriched compost application combined with plant growth-promoting rhizobacteria (PGPR) improves seed quality and nutrient use efficiency of sunflower

Muhammad Saleem Arif, Luca Bragazza, Alexandre Buttler, Muhammad Riaz

Ecological benefits associated with plant growth-promoting rhizobacteria (PGPR) inoculants offer a promising integrated nutrient management option to counteract plant nitrogen (N) deficiency. We performed field experiments to evaluate the effect of integrated N fertilizer regime involving chemical N fertilizer (CNF) and N-enriched compost (NEC), either alone or combined with selected PGPR (Pseudomonas aeruginosa) on sunflower seed quality, N use efficiency (NUE) and soil fertility during 2014-2015. We found that integrated N biofertilizer application resulted in significantly higher seed oil concentration, fatty acid composition, and harvest index in both cropping years. Greater effects on N yield efficiency (NYE), N use efficiency (NUE), N physiological efficiency (NPE), and photosynthetic N use efficiency (PNUE) were recorded in nitrogen-enriched compost+PGPR inoculant (NECPI) treatment followed by chemical N fertilizer+PGPR inoculant (CNFPI) treatment. Statistically significant differences were observed in linoleic and linolenic acid, NYE, and NUE for treatment x year interaction, thus, suggesting that the integrated N biofertilizer approach facilitates the efficient N use by sunflower for improving yield and seed quality. Moreover, we also found considerable enhancement of soil N fertility after two consecutive cropping years of sunflower. The enhancement of seed quality, N use efficiencies, and soil N fertility through integrated N biofertilizer application emphasizes the importance of balanced crop N nutrition, ensuring sufficient N supply to sunflower with adequate N balance in soil for the next crop. Overall, combination of PGPR with NEC amendment may optimize N uptake efficiency and reduce N fertilizer losses, which is necessarily required for the sustainable sunflower production.

Wiley-V C H Verlag Gmbh2017

Interaction of compost additives with phosphate solubilizing rhizobacteria improved maize production and soil biochemical properties under dryland agriculture

Muhammad Saleem Arif, Luca Bragazza, Alexandre Buttler, Muhammad Riaz, Bjorn Jozef Maria Robroek

Dry land soils from the Indo-Gangetic plains are inherently poor in organic matter content and phosphorus (P). Amendment of these soils with P-enriched compost, together with P solubilizing rhizobacterial (PSR) inoculation has been suggested to improve plant growth and P uptake. We performed 3 x 2 factorial experiment using compost i.e. control, raw saw dust P compost (RPC) and acidified saw dust P compost (APC), and PSR inoculation as factors. The pot study investigated the effects of compost and PSR on maize growth, yield, P nutrition and soil biochemical properties. PSR inoculation with APC enhanced shoot length, cob diameter, grain yield and plant P uptake compared to control. APC amendment, either alone or in combination with PSR, also improved root growth and caused extension of rhizosphere by increasing the root length density of the maize plants. Significant improvement in soil biochemical properties i.e. dehydrogenase (DHA), beta-glucosidase (BGA), urease (UA) activity, dissolved organic carbon (DOC), soil organic carbon (SOC) and microbial biomass carbon (MBC) are due to the additive effect of compost amendments. A substantial increase in P availability and associated biochemical attributes reflect the significance of substrate quality, structural stability and optimized pH conditions of added compost that may have enhanced PSR performance, specifically with APC. Moreover, increased carboxylate secretions and PSR abundance in the root zone, lowering of pH and increase in rhizosphere fungal parameters, suggest PSR and APC to be synergetic driving of increased P availability for maize. We conclude that efficiency of P enriched compost could be increased with suitable compost additive in the presence of PSR in dry land soil.

Elsevier2017

Land-use change affects phosphorus fractions in highly weathered tropical soils

Thomas Guillaume

Deforestation and land-use change in tropics have increased over the past decades, driven by the demand for agricultural products. Although phosphorus (P) is one of the main limiting nutrients for agricultural productivity in the tropics, the effect of land-use change on P availability remains unclear. The objective was to assess the impacts of land-use change on soil inorganic and organic P fractions of different availability (Hedley sequential fractionation) and on P stocks in highly weathered tropical soils. We compared the P availability under extensive land-use (rubber agroforest) and intensive land-use with moderate fertilization (rubber monoculture plantations) or high fertilization (oil palm monoculture plantations) in Indonesia. The P stock was dominated by inorganic forms (60 to 85%) in all land-use types. Fertilizer application increased easily-available inorganic P (i.e., H2O-Pi, NaHCO3-Pi) in intensive rubber and oil palm plantations compared to rubber agroforest However, the easily-available organic P (NaHCO3-extractable Po) was reduced by half under oil palm and rubber. The decrease of moderately available and non-available P in monoculture plantation means that fertilization maintains only the short-term soil fertility that is not sustainable in the long run due to the depletion of P reserves. The mechanisms of this P reserve depletion are: 1) soil erosion (here assessed by C/P ratio), 2) mineralization of soil organic matter (SOM) and 3) P export with yield products. Easily-available P fractions (i.e., H2O-Pi, NaHCO3-Pi and Po) and total organic P were strongly positively correlated with carbon content, suggesting that SOM plays a key role in maintaining P availability. Ecologically based management is therefore necessary to mitigate SOM losses and thus increase the sustainability of agricultural production in P-limited, highly weathered tropical soils. (C) 2016 Elsevier B.V. All rights reserved.

Elsevier Science Bv2017