Ibrahim Ortas

Long-Term Phosphorus Application Impacts on Aggregate-Associated Carbon and Nitrogen Sequestration in a Vertisol in the Mediterranean Turkey

Abstract Fertilizers are among major contributors to the production of aboveground and belowground biomass. Soil organic carbon (SOC) concentration is an important factor affecting crop productivity in semiarid clayey soils of low fertility. A long-term experiment was established in 1998 on a Vertisol in the Mediterranean coast of Turkey, to assess the effects of four rates of application of inorganic phosphorus (P) fertilizers (0, 50, 100, and 200 kg P2O5 ha−1) on soil bulk density (&rgr;b), carbon (C) and nitrogen (N) concentrations, SOC and N pools, C and N sequestration rate, aggregate fractions, water-stable aggregates, and the mean weight diameter (MWD). Thus, disturbed and undisturbed soil samples were collected from the 0- to 15-cm depth after wheat (Triticum aestivum L.) harvest in June 2010 to analyze soil properties. Increase in the rate of application of P fertilizers significantly increased &rgr;b and reduced porosity (%). The SOC concentration was significantly more in the treatment receiving 200 kg P2O5 ha−1 than in the control. The carbon-nitrogen ratio was less than 10 in control and greater than 10 in high P fertilizer treatments. Total amount and rate of C and N sequestration increased with increase in the rate of application of P fertilizers. The mean rate (kg C ha−1 y−1) of C sequestration was −110.9 for control and 556.9 for the highest rate of P fertilizer. Increase in fertilizer rate also significantly increased the rate (kg N ha−1 y−1) of N sequestration, which was −0.21 for control and 28.9 for the highest rate of P fertilizer treatment. The SOC concentrations differed among aggregate-size fractions, which were greater in 0.5- to 2.0-mm aggregate size than those in the fraction of less than 0.25 mm. Greater SOC concentrations were observed in 1- to 2-mm and 0.5- to 1-mm size fractions than in fractions of less than 0.25 mm. Concentrations of C and N decreased significantly with decrease in aggregate size of less than 0.25 mm. There was a general trend of increase in water-stable aggregates and MWD with increase in application of P fertilizer. The highest MWD (1.81 mm) was observed in the high P rate and lowest (1.36 mm) in the control. Macroaggregates were more enriched in C and N than microaggregates. The mean rate of SOC sequestration with 200 kg P2O5 ha−1 treatment is ∼560 kg C ha−1 y−1. The effects of long-term P fertilizer application on C and N sequestration finding(s) of from this study have not been previously observed.

Changes in soil ergosterol content, glomalin-related soil protein, and phospholipid fatty acid profile as affected by long-term organic and chemical fertilization practices in Mediterranean Turkey

The present study examines the effects of different fertilization treatments (chemical fertilization, farmyard manure, plant compost, and mycorrhiza-inoculated compost) on the soil fungi under a crop rotation of wheat (Triticum aestivum L.) and corn (Zea mays L.) in a long-term field experiment established in Mediterranean Turkey in 1996. Soil samples were collected in May, August, and October 2009. Soil pH, organic carbon, plant-available nitrogen and phosphorus, mycorrhizal colonization, and a series of biochemical markers (phospholipid and neutral lipid fatty acid [PLFA and NLFA] profiles, soil ergosterol content, and glomalin related soil protein [GRSP] as indicators of abundance of bacteria, saprotrophic, and arbuscular mycorrhizal [AM] fungi) were assessed. No significant difference was observed in soil organic C and plant available N in relation to long-term fertilization treatments, but plant available P in soil changed significantly in relation to the fertilization treatment used and the sampling season (between 11.5–33.8 mg · kg−1 in spring, 10.4–28.6 mg · kg−1 in summer, and 10.5–33.2 mg · kg−1 in autumn). Mycorrhizal colonization patterns were similar for both plants. However, mycorrhiza-inoculated compost treatment exhibited higher root colonization (77.3%) over control (16.3%), chemical fertilization (10.0%), farmyard manure (19.3%), and plant compost (20.0%). No statistically significant change was observed in ergosterol content. The effect of long-term organic treatments on soil PLFA structure was statistically prominent; whereas seasonality only affected bacterial PLFAs. Organic fertilization increased GRSP (mean annual ranging from 0.91 to 2.46 mg · g−1 total GRSP) but long-term annual mycorrhizal inoculation had no significant effect on the soil GRSP pool.

Long-term fertilization effect on agronomic yield and soil organic carbon under semi-arid Mediterranean region.

Management practices, including use of organic and inorganic fertilizers, significantly affect soil organic carbon (SOC) pool and agronomic yield. Crop yields in semi-arid regions of Turkey are declining because of depletion of SOC pool and the attendant decline in soil quality. Thus, this study was conducted to assess the effects of inorganic and organic fertilizer treatments (control, chemical fertilizer, animal manure, compost and compost + mycorrhizal inoculation) on SOC pool and agronomic yield in a long-term field experiment initiated in 1996 on the Mediterranean coast of Turkey. The SOC pool under different soil fertilizer management treatments was related to agronomic yield of pepper, wheat and maize. Biomass production increased as the SOC concentration increased with the application of organic and mineral (inorganic) fertilizers compared with the control. Between 1996 and 2010, the SOC concentration in 0-15 cm depth of the unfertilized control decreased from 0.96% to 0.87%. In comparison, SOC concentration increased in treatments amended with organic fertilizers such as manure, compost and compost+mycorrhzae. Agronomic yield was also significantly affected by Original Research Article American Journal of Experimental Agriculture, 4(9): 1086-1102, 2014 1087 organic and inorganic fertilizer treatments, which declined over time in the control but increased in treatments receiving compost, manure and compost + mycorrhizae. The negative regression was obtained in control treatments between SOC and the wheat yield (Y = -1.18x + 3.84, R=0.205) and maize yield (Y = -1.28x + 7.56, R=0.016). Additional research is needed to assess the role of fertilizers on SOC concentration and its effects on agronomic yields under long-term soil and crop management systems especially with mycorrhizal inoculation.

Enhancement of maize plant growth with inoculation of phosphate-solubilizing bacteria and biochar amendment in soil

ABSTRACT Maize plant has an absolute requirement of nutrients (N, P, and K) for growth and development. The microbial application can facilitate in addressing limited access to chemical fertilizer concern. Moreover, biochar and phosphorus-solubilizing bacterial (PSB) community can contribute together in nutrient availability. Both have the P-supply potential to the soil, but their interaction has been tested less under semiarid climatic conditions. The purpose of the study was to evaluate the potential of biochemically tested promising PSB strains and biochar for maize plant growth and nutritional status in plant and soil. Therefore, two isolated PSB strains from maize rhizosphere were biochemically tested in vitro and identified by 16S rDNA gene analysis. The experiment was conducted in the greenhouse where the plant growth and nutrient availability to the plants were observed. In this regard, all the treatments such as PSB strain-inoculated plants, biochar-treated plants, and a combination of PSBs + biochar-treated plants were destructively sampled on day 45 (D45) and day 65 (D65) of sowing with four replications at each time. PSB inoculation, biochar incorporation, and their combinations have positive effects on maize plant height and nutrient concentration on D45 and D65. In particular, plants treated with sawdust biochar + Lysinibacillus fusiformis strain 31MZR inoculation increased N (32.8%), P (72.5%), and K (42.1%) against control on D65. Besides that, only L. fusiformis strain 31MZR inoculation enhanced N (23.1%) and P (61.5%) than control which shows the significant interaction of PSB and biochar in nutrient uptake. PSB and biochar have the potential to be used as a promising amendment in improving plant growth and nutrient absorption besides the conventional approaches.

The Effect of Mycorrhiza Inoculation and Phosphorus Application on Phosphorus Efficiency of Wheat Plants

ABSTRACT The effect of indigenous soil and selected mycorrhizal inoculation and phosphorus (P) applications on wheat yield, root infection and nutrient uptake was monitored for two successive years under field conditions. In addition, phosphorus efficiency and inoculation effectiveness (IE) were determined. Wheat (Triticum aestivum L.) plants were used as host plants in a Menzilat soil series (Typic Xerofluvents) in the Mediterranean coastal region of Turkey. Three levels of phosphorus were applied with Glomus mosseae to wheat plants over two successive years. Mycorrhizal inoculation significantly increased root colonization. G. mosseae-inoculated plants in both years exhibited a two-fold higher root colonization than the indigenous mycorrhizal colonization. Compared with non-inoculated plants, mycorrhizal inoculation increased wheat yield for both years. In addition, increasing P fertilizer levels enhanced the wheat grain yield. In both years, the inoculum efficiency (IE) decreased with increasing P level addition. Phosphorus efficiency is higher under low P application than the higher P application. However, with mycorrhizal inoculation P efficiency is higher than the non-inoculated treatment. The effects of mycorrhizal inoculation on plant nutrient concentrations were determined: mycorrhiza-inoculated plants exhibited a higher zinc (Zn), manganese (Mn), copper (Cu), iron (Fe) nutrients concentration than non-inoculated plants. After two years of field experiments, it is concluded that mycorrhizal inoculation can be used in large arable areas; however, it is also very important to manage the indigenous mycorrhiza of arable land.

Phosphorus Fertilization Impacts on Corn Yield and Soil Fertility

ABSTRACT Optimization of phosphorus (P) fertilization is important for balancing soil fertility especially in vertisol to support economic crop production. The objective of the study was to determine the impact of P fertilization (1998 to 2014) on crop yield and nutrient uptake, and soil fertility under continuous annually tilled corn (Zea mays L.)-wheat (Triticum aestivum L.) system in semi-arid Mediterranean conditions. The study was conducted on Arik clay (isohyperthermic, fine clay Typic Haploxerert) using randomized complete block design with four replications for each treatment at the research farm of the Dept. of Soil Science and Plant Nutrition, Çukurova University, Adana, Turkey. P fertilizer at 0, 50, 100, 200 kg P2O5 ha−1 as triple superphosphate (TSP), respectively was applied a week before planting corn. Results showed that increasing P fertilization rates significantly decreased the number of mycorrhizal spores associated with corn roots. Similarly, a 10% decrease in corn root mycorrhizal colonization was observed with 200 kg P2O5 ha−1 fertilization. In the control treatment, corn yield was 4.3 Mg ha−1 as compared to 5.6, 5.7 and 6.1 Mg ha−1 in 50, 100 and 200 kg of P2O5/ha, respectively. The relationship between P fertilization and relative yield showed that more than 95% of the corn yield was produced when P applied at 100 kg P2O5 ha−1. While P fertilization significantly increased the leaf N, P, and K contents but decreased the leaf Zn, Fe and Mn contents, as compared with the control. However, P fertilization did not consistently affect the grain N and P contents. Both physiological efficiency- and agronomic efficiency of P fertilization have shown a significant non-linear increase than that of the control. Total organic C (TOC) and total N (TN) concentrations were more than 34 and 26% higher in 100 and 200 kg P2O5 ha−1rates as compared with the control. Likewise, available P (AP), manganese (Mn) and zinc (Zn) concentrations increased with an increase in P fertilization rates. The AP, Mn and Zn contents significantly stratified by P fertilization. Our results suggested that 100 kg P2O5 ha−1 is optimum to sustain Vertisol fertility for supporting economic corn production in the Mediterranean climates of Turkey.

Carbon Sequestration and Mycorrhizae in Turkish Soils

The atmospheric carbon dioxide (CO2) concentration has increased by 31 % since the onset of industrial revolution around 1850, from 280 ppm/year to 400 ppm/year in 2013. Chemical fertilizers, pesticides, tillage, irrigation and seed use improvements have increased agricultural production. Moreover, agricultural mismanagement may have affected atmospheric CO2 through the intensified degradation of soil organic matter (SOM). Water deficiency, high temperatures and land degradation could be the result of increasing atmospheric CO2 concentrations, particularly in semi-arid Mediterranean regions. High temperatures, decreased water availability and post-harvest straw burning in preparation for the next crop reduce the soil organic carbon (SOC). Note that soil quality and productivity are also declining. In addition, the intensity of climate change is expected to increase. Soil provides a sink for atmospheric CO2 and therefore reduces net CO2 emissions associated with agricultural ecosystems, mitigating the ‘greenhouse effect’. There are several techniques to mitigate atmospheric CO2. One approach involves fixing atmospheric CO2 via the natural process of photosynthesis in terrestrial ecosystems (soil and biota). Plants fix atmospheric CO2 in soil and biota because plant roots and mycorrhizal fungi require carbon (C) and contribute to C sequestration (CSQ). Therefore, small changes in the soil C cycle could have large impacts on atmospheric CO2 concentrations. Arbuscular mycorrhizal fungi (AMF) are obligate symbionts of most plant species, and they are important for soil aggregation and stabilization. Mycorrhizae fungi are the major component of soil microbial biomass. AMF hyphae produce glomalin that contains C and that is an important part of the terrestrial C pool. The effects of mycorrhizal colonization on nutrient uptake and root growth have been extensively studied. CSQ and aggregate C storage have become priority topics in soil science since 1990s. Interest in the effects of mycorrhizal hyphae (glomalin as the by-product) and humic substances that enhance aggregate stability is increasing. AMF play a key role in soil aggregate formation and stabilization. This long-term experiment was established in 1996 to assess crop and soil management effects on mycorrhizal development and SOC accumulation. The principal objective was to determine how soil management affects indigenous mycorrhizae and SOC dynamics. Results show that mycorrhizal colonization and sporulation depend on soil and crop management and that soil aggregate development is affected by SOC content and mycorrhizal presence.

The Mechanisms of Nutrient Uptake by Arbuscular Mycorrhizae

Mycorrhizal fungi are one of the commonly occurring living organism in soil facilitating plants in growth, development, stress tolerance, soil pollutants remediation, C-sequestration, food security and agricultural sustainability. Mycorrhizal fungi assist the plants in nutrient absorption by extending mycorrhizal hyphae network beyond the rhizosphere. Mycorrhizal inoculation alters the root architecture and studies showed that nutrient absorption capacity of inoculated root is much better than non-inoculated. For a long time, it is assumed that roots absorb nutrients only through direct pathway (DP) only while contribution of AM fungi in nutrients uptake by mycorrhizal pathway (MP) has been ignored. But now the development in scientific methods and tools, enabled the researcher to explore MP mechanism for macro and micro nutrients, moreover suppression of heavy metal stress to the plants. Besides that, mycorrhizal fungi obtain around 20% of photosynthesized C from the plant in exchange of nutrients. Moreover, this C triggers nutrient uptake and their translocation. Plant hormones and root exudates also influence the infection formation and development, they also point out new sites for the interaction of mycorrhizal fungi and plant roots. Nutrient mobility by MP is more secure and economical than DP. Understanding about the nutrient exploration, mobilization, and uptake in root-mycorrhizal interaction has been discussed here at molecular level. Contribution of plant and mycorrhizal transporters have been discussed which need further understanding. Also contribution of mycorrhizal inoculation on nutrient uptake compared with non-inoculated roots were discussed.

Application of Arbuscular Mycorrhizal Fungi into Agriculture

In the natural ecosystem, rhizospheric soils have various biological organisms to favour the plant growth, nutrient absorption, stress tolerance, disease prevention, carbon capturing and many more. These organisms include mycorrhizal fungi, bacteria, actinomycetes, etc. which solubilize nutrients and assist the plants in uptaking by roots. Among them, arbuscular mycorrhizal (AM) fungi have key importance in natural ecosystem, but high rate of chemical fertilizer in agricultural fields is diminishing its importance. In this chapter, indigenous AM fungi efficiency is discussed with various doses of chemical fertilizer against number of cereal, cash, horticultural and fruit crops. Moreover, their effects on the plant growth, yield enhancement, fruit quality and soil quality are discussed. In the rhizosphere, AM fungi have main interaction with multipurpose bacteria such as phosphorus solubilizing bacteria, nitrogen fixers, plant growth-promoting rhizobacteria and stress tolerance bacteria. AM fungi contribute in building rhizospheric carbon stock, and, recently, addition of biochar in the soil for enhancing soil physicochemical properties and nutrient release has been studied with AM fungi. In order to manage the indigenous AM fungal spores, soil and crop management is important in association with carbon amendments for soils. One of the greatest challenges for the society is food insecurity, which should be changed into ‘food security’ by improving our knowledge and practicality to double the food production through sustainable farming approaches.

Arbuscular Mycorrhizae: Effect of Rhizosphere and Relation with Carbon Nutrition

More than 90 % of terrestrial plants form symbiotic association with mycorrhizae which develop and promote cooperation belowground in rhizosphere. Mycorrhizal fungi produces spores in the soil and vegetative propagules in root fragments which respond to stimulation of root exudates in the rhizosphere. As a result, symbiotic relationship takes place where physiology and morphology of both participants rely on each other. Mycorrhizae are present in a range of horticultural, agricultural, forestry and other plant species. Along with mycorrhizae, other beneficial microbes also add in plant growth promotion, nutrient and uptake and stress tolerance either biotic or abiotic. The presence of bacteria in rhizosphere synchronizes with mycorrhizae termed as ‘mycorrhizae helper bacteria’ and increases plant growth by focusing on N and P in particular while micronutrients in general. Besides that, carbon has important structural and functional role in symbiotic association, because of mycorrhizal reliance on plants for food. Additionally, movement of C to the roots is an interesting area for exploration due to recent global focus on addressing climate change and carbon mitigation approaches particularly for sustainable agriculture. AM symbiosis can influence soil CO2 emissions and soil in ecosystems dominated by mycorrhizal plants that contain 70 % more carbon per unit nitrogen than soil in ecosystems dominated by non-AM-associated plants. Absorption of CO2 by mycorrhizae is contributing in climate change mitigation and translated as plant biomass production.