Soil carbon, nitrogen and phosphorus dynamics as affected by solarization alone or combined with organic amendment

Soil solarization, alone or combined with organic amendment, is an increasingly attractive approach for managing soil-borne plant pathogens in agricultural soils. Even though it consists in a relatively mild heating treatment, the increased soil temperature may strongly affect soil microbial processes and nutrients dynamics. This study aimed to investigate the impact of solarization, either with or without addition of farmyard manure, in soil dynamics of various C, N and P pools. Changes in total C, N and P contents and in some functionally-related labile pools (soil microbial biomass C and N, K2SO4-extractable C and N, basal respiration, KCl-exchangeable ammonium and nitrate, and water-soluble P) were followed across a 72-day field soil solarization experiment carried out during a summer period on a clay loam soil in Southern Italy. Soil physico-chemical properties (temperature, moisture content and pH) were also monitored. The average soil temperature at 8-cm depth in solarized soils approached 55 C as compared to 35 C found in nonsolarized soil. Two-way ANOVA (solarization organic amendment) showed that both factors significantly affected most of the above variables, being the highest influence exerted by the organic amendment. With no manure addition, solarization did not significantly affect soil total C, N and P pools. Whereas soil pH, microbial biomass and, at a greater extent, K2SO4-extractable N and KCl-exchangeable ammonium were greatly affected. An increased release of water-soluble P was also found in solarized soils. Yet, solarization altered the quality of soluble organic residues released in soil as it lowered the C-to-N ratio of both soil microbial biomass and K2SO4-extractable organic substrates. Additionally, in solarized soils the metabolic quotient (qCO2) significantly increased while the icrobial biomass C-to-total organic C ratio (microbial quotient) decreased over the whole time course. We argued that soil solarization promoted the mineralization of readily decomposable pools of the native soil organic matter (e.g. the microbial biomass) thus rendering larger, at least over a short-term, the available fraction of some soil mineral nutrients, namely N and P forms. However, over a longer prospective solarization may lead to an over-exploitation of labile organic resources in agricultural soils. Manure addition greatly increased the levels of both total and labile C, N and P pools. Thus, addition of organic amendments could represent an important strategy to protect agricultural lands from excessive soil resources exploitation and to maintain soil fertility while enhancing pest control

An attempt to model the induction and feedback inhibition of nitrate uptake in wheat seedlings

The aim of the present study was to develop a mathematical model in attempt to describe the induction and feedback inhibition phases of nitrate uptake in wheat (Triticum durum L. cv. Appulo) seedlings. The model proposed is based on three autonomous, non-linear, and time-dependent differential equations showing good agreement with our experimental data. The model could be fruitfully applied for a correct evaluation of different patterns of nitrate uptake owing to genetic and physiometabolic plant characteristics and external nutrient availability

Genetic analysis of root adaptive traits in sugar beet

Genetic improvement of sugar beet requires better knowledge of genetic basis of root adaptive traits to nutritional stress. This study was conducted to determine combining ability and heritability for morphological and physiological root traits involved in nutrient acquisition in a diallel set of crosses of 5 sugar beet genotypes. Total root length, root surface area, number of root tips, glucose and fructose concentration in the root tips, and sulfate uptake rate were evaluated after sulfate deprivation on six-teen day old seedlings grown under hydroponic conditions. Significant differences were observed among genotypes for the morphological and physiological traits evaluated, and such traits were significantly correlated with the productivity. The genetic analysis showed that general and specific combining ability effects were significant for all traits, with a predominance of additive gene effects. All traits exhibited high coefficients of heritability, suggesting their response to the selection process. The inheritance of the investigated traits could be considered in breeding programs aimed at increasing sugar yield under nutritional stress