Occurrence of Cu and Cr in the sedimentary humic substances and pore water from a typical sugar cane cultivation area in São Paulo,Brazil

Purpose

The purpose of this paper is to study the interactions of sedimentary humic substances (SHS) from a sugarcane cultivation area with Cu(II) and Cr(III) and to evaluate the occurrence of these metals in the pore water and SHS.

Materials and methods

For this study, the northwestern region of the State of São Paulo, Brazil, which is considered the region with the highest production of sugar cane in the state, was selected. Samples of sediment were collected from four sampling sites in the Preto, Turvo, and Grande rivers. The SHS and pore water were extracted from the sediment using the method suggested by the International Humic Substances Society and centrifugation, respectively. The complexing capacity (CC) of the SHS for Cu(II) and Cr(III) was determined by individually titrating these metals with an ultrafiltration system using tangential flow. The total concentrations of Cr and Cu were determined for the pore water, sediments, and humic substances with graphite furnace atomic absorption spectrometry and Zeeman background correction after an acid digestion, according to the methods described in US EPA Method 3050B.

Results and discussion

The SHS from a site in the Turvo River, which is typically cultivated with sugarcane, possessed the highest concentration of Cu bound to SHS (25.0%), the largest CC (0.63 mmol Cu g^?1 HS) and the highest concentration of this metal in the pore water (1.38 mg Cu Kg^?1 sed.). For Cr, the SHS collected from a location on the Preto River dam had the largest CC (0.90 mmol Cr g^?1 HS) and the lowest Cr content in the pore water (0.29 mg Cr Kg^?1 sed.), indicating that there was an inverse relationship between the CC and the concentration of metal available in the pore water.

Conclusions

Sedimentary humic substances might be one of the regulatory factors controlling the availability of Cu and Cr in the sediments found in a typical region that has been planted with sugarcane. Distinct behaviors were observed between the two elements investigated; higher CC and a larger fraction of Cu(II) were found in the pore water of samples originating from sugarcane crops. The opposite behavior was observed for the Cr(III) species.     

Iron deficiency studies of sugar beet using an improved sodium bicarbonate‐buffered hydroponic growth system

A sodium bicarbonate (NaHCO₃)‐buffered hydroponic growth system was developed that simulates alkaline soil growth conditions necessary to screen sugar beet genotypes for iron (Fe) efficiency character. Three genotypes (NB1, NB4, and F, hybrid, NB 1xNB4) with differing capacities for Strategy I Fe responses were phenotyped successfully using this system. Genotypes NB1 and NB1xNB4 are Fe efficient, while NB4 is Fe inefficient. It was demonstrated that 5 mM NaHCO₃ provided buffering within an optimal range (pH 7.3 ‐ pH 6.3) for the duration of ‐Fe treatments, promoted enhanced H⁺ extrusion, and increased the in vivo capacity for Fe³⁺‐chelate reduction (Fe³⁺‐chelate reductase [FCR] activity), especially in the roots of the Fe efficient genotypes. The same concentrations of NaHCO₃ did not interfere with Fe supply to +Fe control plants of any genotype. The in vivo capacity for Fe³⁺‐chelate reduction increased over fivefold in both Fe efficient genotypes (NB1 and NB 1xNB4), but just under twofold in the Fe inefficient genotype (NB4). Localization and duration of enhanced Fe³⁺‐chelate reduction capacity were dependent upon the Fe efficiency character of each genotype.     

Soil organic carbon as affected by direct drilling and mulching in sugar beet – wheat rotations

The effect of conventional ploughing, mulching, and direct drilling on the soil organic C (soil C_org) contents through the soil profile and on total soil C_org stocks (0–45 cm) was investigated at five different German sites. All sites showed similar results: after 10–13 years, soil C_org contents in the surface soil (0–10 cm) were 15–71% and 33–42% higher under direct drilling and mulching, respectively, than under ploughing (8–18 g kg^?1). Under ploughing, the soil C_org contents were distributed homogenously through the soil profile. Either mulching or direct drilling resulted in 3–28% higher soil C_org stocks than ploughing (49–116 t ha^?1). However, the tillage management was no significant factor since the sites showed the effects to different extents but were the mathematical replications. Five to six years later, trends and values were similar. We concluded that the main effect of mulching or direct drilling was the stratification with higher soil C_org contents in the surface soil. Since this is a positive means for soil protection, we suggested that the use of mulching or direct drilling can contribute to a sustainable soil management in crop rotations with sugar beet which are characterized by a strong physical impact on the soil during harvest.     

Soil losses due to harvesting of chicory roots and sugar beet: an underrated geomorphic process?

Field observations in central Belgium indicate a significant soil degradation process which has hitherto not been considered in assessments of soil erosion rates: i.e., soil losses due to root crop harvesting (SLRH). The objectives of this study were: (1) to assess SLRH for two commonly grown root crops in Belgium, i.e. chicory roots and sugar beet, (2) to investigate some factors controlling the spatial and temporal variation of SLRH, and (3) to evaluate the contribution of this soil degradation process to overall soil loss in the study area. Soil losses due to harvesting of witloof chicory roots were assessed by measuring dirt tare from 43 root samples whereas SLRH for inuline chicory roots and sugar beet were calculated from dirt tare data provided by factories processing these roots. Mean soil loss was 11.8 ton ha⁻¹ harvest⁻¹ for witloof chicory roots, 8.1 ton ha⁻¹ harvest⁻¹ for inuline chicory roots and 9.1 ton ha⁻¹ harvest⁻¹ for sugar beet. Assuming that root crops are grown once in 2 years in the study area, mean annual SLRH equals 5.0 ton ha⁻¹ year⁻¹ (0.33 mm/year). Since these root crops have been grown over a period of at least 200 years in Belgium, this implies a mean soil profile truncation of 66 mm. However, important spatial and temporal variability in SLRH data was observed, depending on soil texture, soil moisture at harvest time and harvesting technique. Given the importance of SLRH, it needs to be incorporated into future assessments of soil degradation processes and sediment budgets.     

Population and distribution of sclerotia of Rhizoctonia solani kühn in sugar beet field soil

The population and distribution of sclerotia of Rhizoctonia solani Kühn in two sugar beet field soils was determined at harvest by a sieving-flotation method. In rhizosphere soil (RS) and non-rhizosphere soil (NRS) from the most heavily infected roots of sugar beets, 1.43–2.5 and 0.83–1.0 sclerotia g^?1 dry soil were detected, respectively. In the soil around healthy sugar beet, these values were 0.04–0.12 and 0.03–0.04 sclerotia g^?1 dry soil. More sclerotia were always obtained from RS than from NRS. More than 80% of the sclerotia were in the upper 10 cm of soil and within 10 cm of diseased roots. Therefore, there is a non-uniform distribution of sclerotia of R. solani in soil.The sclerotial population in soil increased significantly with disease severity and a good correlation was obtained between the number of sclerotia and the disease severity on infected plants. Most of the sclerotia collected from the field soil ranged in size from 0.5 to 2.0 mm diameter.Viability of sclerotia increased as severity of crown rot increased and as the size of the sclerotia increased. Conversely, there was a progressive decrease in sclerotial germination with increasing depth in soil and increasing distance from the infected root.     

Relationship of seed pericarp color with seed quality in sugar beet (Beta vulgaris L. var. altissima Döll)

Genetic Resources and Crop Evolution - Quantitative traits of seed pericarp color were used to evaluate the sugar beet (Beta vulgaris L.) seed quality. These traits were measured on 10 single cross...     

How does tomato quality (sugar, acid, and nutritional quality) vary with ripening stage, temperature, and irradiance?

The objective of this study was to understand the respective impact of ripening stage, temperature, and irradiance on seasonal variations of tomato fruit quality. During ripening, concentrations in reducing sugars, carotenes, ascorbate, rutin, and caffeic acid derivates increased, whereas those in titratable acidity, chlorophylls, and chlorogenic acid content decreased. Fruit temperature and irradiance affected final fruit composition. Sugars and acids (linked to fruit gustative quality) were not considerably modified, but secondary metabolites with antioxidant properties were very sensitive to fruit environment. Increased fruit irradiance enhanced ascorbate, lycopene, beta-carotene, rutin, and caffeic acid derivate concentrations and the disappearance of oxidized ascorbate and chlorophylls. Increasing the temperature from 21 to 26 degrees C reduced total carotene content without affecting lycopene content. A further temperature increase from 27 to 32 degrees C reduced ascorbate, lycopene, and its precursor's content, but enhanced rutin, caffeic acid derivates, and glucoside contents. The regulation by light and temperature of the biosynthesis pathways of secondary metabolites is discussed.     

Effects of genotype, latitude, and weather conditions on the composition of sugars, sugar alcohols, fruit acids, and ascorbic acid in sea buckthorn (Hippophaë rhamnoides ssp. mongolica) berry juice

Sea buckthorn berries (Hippopha? rhamnoides ssp. mongolica) of nine varieties were collected from three growth locations in five inconsecutive years (n = 152) to study the compositional differences of sugars, sugar alcohols, fruit acids, and ascorbic acid in berries of different genotypes. Fructose and glucose (major sugars) were highest in Chuiskaya and Vitaminaya among the varieties studied, respectively. Malic acid and quinic acid (major acids) were highest in Pertsik and Vitaminaya, respectively. Ascorbic acid was highest in Oranzhevaya and lowest in Vitaminaya. Berry samples of nine varieties collected from two growth locations in five years (n = 124) were combined to study the effects of latitude and weather conditions on the composition of H. rhamnoides ssp. mongolica. Sea buckthorn berries grown at lower latitude had higher levels of total sugar and sugar/acid ratio and a lower level of total acid and were supposed to have better sensory properties than those grown at higher latitude. Glucose, quinic acid, and ascorbic acid were hardly influenced by weather conditions. The other components showed various correlations with temperature, radiation, precipitation, and humidity variables. In addition, fructose, sucrose, and myo-inositol correlated positively with each other and showed negative correlation with malic acid on the basis of all the samples studied (n = 152).