Concentration In Corn Research Articles

Redox Behavior of Zearalenone in Various Solvents

The redox equilibriums involving zearalenone were studied by cyclic and differential pulse voltammetry on a glassy carbon electrode. The cyclic voltammograms of zearalenone in DMSO at a glassy carbon electrode in the potential range from −600 to 1400 mV vs. the Ag/AgCl have two oxidation peaks and a reduction one. Zaralenone concentration may be determined by DPV at +1050 mV. The method was applied to the determination of zearalenone concentration in corn, barley, and maize. Studies performed in aqueous solution or in mixed solvents water-acetonitrile containing 1 M H2SO4 showed that the oxidation of ZEN with an aqueous solution of Ce(IV) at room temperature, in the dark, occurs with the destruction of ZEN molecule. Studies performed in aqueous solution or in mixed solvents water-acetonitrile containing 1 M H2SO4 showed that the oxidation of ZEN with an aqueous solution of Ce(IV) at room temperature, in the dark, occurs with the destruction of ZEN molecule.

Corn Silage Growth and Yield after Application of Dairy Manure with High Copper Concentrations

Dairy producers use footbaths containing CuSO4 for the prevention of papillomatous digital dermatitis. After cows (Bos taurus) have passed through the footbath, waste is usually disposed of into manure storages and applied to fields. The objectives of this research were to evaluate the effects of the application of high‐Cu dairy manure on growth and yield of corn (Zea mays L.) for silage and to evaluate the accumulation of Cu in the soil. Manure was collected, CuSO4 was added, and all plots received approximately 105.9 L of manure (53,572 L ha−1). A control (0.38 kg Cu ha−1), medium Cu (9.5 kg Cu ha−1), and high Cu (18.6 kg Cu ha−1) treatments were applied to the same plots in 2006 and 2007. An early maturity and late maturity corn hybrid was used each year. Soil samples from 0 to 15 cm were analyzed for solution, extractable, and total Cu. Soil samples from 15 to 46 cm were analyzed for solution and total Cu. The growth, yield, forage quality, and Cu concentration of corn were not affected by treatments. Soil extractable and total soil Cu increased linearly as Cu application increased (P < 0.001). Soil solution Cu increased as Cu treatment rate increased, but was not linear (P = 0.04). Solution and total soil Cu were not different as sampling depth increased. Two annual applications of high‐Cu dairy manure at rates relative to agronomic practices did not affect corn grown for silage and resulted in no vertical movement of Cu in the soil.

돈분의 자원화 퇴비 제조 방법 및 작물 재배 안전성 검정

본 연구는 돈분슬럿지에 함유되어 있는 구리와 아연을 제거하여 합리적인 돈분슬럿지 자원 화비료 생산법을 연구하였고 돈분슬럿지 자원화비료를 시비 후 옥수수를 재배한 토양과 식물체를 분석하여 돈분슬럿지 자원화비료의 안정성을 조사한 바 그 결과는 다음과 같다. 돈분슬럿지의 화학적 특성 중 비효성분으로는 질소와 인산의 함량이 각각 4.4%와 6.29%이며 pH는 7.57로써 작물의 생육에 적합수준이나 돈분슬럿지에 함유되어 있는 중금속인 구리와 아연의 함량은 각각 805mg/kg, 1,704mg/kg으로 비료의 제한기준인 300mg/kg, 900mg/kg 보다 높아 적절한 퇴비화과정을 거치치 않고 토양에 직접 시비하였을 경우에는 토양에 중금속 집적이라는 토양오염을 유발할 소지가 있다고 사료된다. 유기산 9종류를 제조하여 중금속을 제거한바 구연산1수화물의 경우에는 구리 58%, 아연 97%를 제거하였고 옥살산2수화물의 경우에 는 구리와 아연 각각 48%, 56%의 제거율을 보인바 구연산1수화물을 구리와 아연의 제거용액으로 선정하고 증류수에 유기산용액의 혼합비율을 25%, 50%, 75%, 100% 4가지 수준으로 나누어 구리와 아연의 중금속 제거율을 측정한 바, 유기산용액의 혼합비율이 많아질수록 구리와 아연의 제거율이 정의상관관계를 나타내고 있으며 유기산용액 100% 수준에서는 돈분슬럿지의 잔존 구리와 아연의 함량은 330.03mg/kg, 41.28mg/kg로 구리의 경우에는 59% 아연의 경우에는 97%의 제거율을 나타내고 있다. 교반식 퇴비화과정으로 돈분슬럿지의 자원화 처리를 진행한 바 교반식 퇴비화 과정이 정체식 퇴비화 과정에 비하여 안정화 기간이 짧았고 이러한 안정화 단계는 온도변화에서 확인할 수 있는데 교반식의 경우에는 최고의 온도가 <TEX>$4^{\circ}C$</TEX> 더 높게 나타났으며 안정화 최종단계라고 판단할 수 있는 온도 하강의 경우에도 교반식이 정체식에 비하여 7일 빠르게 진행된 것으로 나타난 바 교반식 퇴비화과정이 정체식 퇴비화과정보다 효율이 높다고 사료된다. 구연산1수화물로 돈분슬럿지의 구리와 아연을 제거한 후 돈분슬럿지의 pH가 강산성 수준인 2 이하로 낮아졌는데 이는 돈분슬럿지가 저유기산이라도 구연산1수화물에 48시간동안 접촉하는 과정에서 화학적 특성이 변화된 것으로 사료되며, pH를 조절하기 위하여 소석회와 부자재를 혼합하여 퇴비화과정을 진행하여야 자원화비료로써의 활용가치가 높아진다. pH, EC 및 함수율의 안정화는 교반식 퇴비화과정이 정체식 퇴비화과정보다 빠르게 나타났다. 식물발아 실험인 Germination index 지수에서도 확인가능한데 교반식의 경우에는 안정화 단계의 기준인 Germination index 지수 80의 도달시점이 3주이내보다 정체식의 경우에는 4주 이후에 안정화기준인 80이 관찰되었다. 그러므로 생산기간의 단축에 의한 생산비 절감측면에서 볼 때 정체식 퇴비화공정보다는 교반식 퇴비화과정이 돈분슬럿지의 자원화비료 생산에 합리적인 퇴비화방법이라고 사료된다. 중금속의 함유량 등을 조사하여 토양과 사일리지 옥수수의 체내 안정성을 검사한바 옥수수 재배 후에 토양의 구리와 아연의 함량은 구연산1수화물로 중금속을 제거한 처리구2의 경우에는 구리, 아연의 함량이 각각 2.40mg/kg, 4.26mg/kg으로 돈분슬럿치만을 시비한 처리구3의 구리와 아연의 함량 8.00 mg/kg, 22.37mg/kg에 비하여 낮은 수준으로 나타나고 있다. 식물체인 청안옥의 중금속 함량도 식물체 부위별로 돈분슬럿지만을 시비한 처리구3이 구연산 1수화물로 중금속을 제거한 처리구2 보다 최소2배에서 최대 4배까지 높았다. This study was carried out development a new composting system to lower copper and zinc concentration in plg sludge compost and conduct an inquiry into the possibility of crop cultivation. The concentrations of nitrogen, phosphorus and pH averaged 4.4%, 6.3% and 7.57, respectively, which were higher concentrations than in commercial organic fertilizers, and the concentrations of copper and zinc averaged 805 and 1,704 mg/kg, respectively, which were beyond the heavy metal concentration limit in byproduct compost. Hydrated citric acid I lowered the concentrations of copper and zinc by 58% and 97%, respectively and hydrated oxalic acid II lowered the concentrations of copper and zinc by 48% and 56%, respectively in pig sludge compost. Lower concentrations of copper and zinc in pig sludge resulted from the enhanced hydrated-citric acid concentration in organic acid solution mixed with distilled water. The concentrations of copper and zinc were 330, and 41 mg/kg in the pig sludge treated with 100% hydrated citric acid. Agitation composting system stabilized the compost earlier than the stationary composting system, in which the stabilization condition was confirmed by higher temperature by <TEX>$4^{\circ}C$</TEX> at highest temperature and 7 days earlier cooling down after highest temperature. The levels of germination index (G.I) 80 were obtained 15 and 20 days after composting in agitation and stationary composting system, respectively. The concentrations of copper and zinc were 2.4 and 4.26 mg/kg respectively in soils amended with pig sludge compost after removing process of heavy metals by citric acid, but 8.0 and 22.37 mg/kg, respectively in soils amended with Pig Sludge. The concentrations of heavy metals was highest in com cultivated in soils amended with pig sludge. The copper and zinc concentrations In corn leaves were 75.2 and 50.56 mg/kg respectively, which were 4 and 2 fold higher than the com cultivated in soils amended with pig sludge compost after heavy metal removing process by hydrated citric acid.

Effect of Plant Density on Forage Yield and Quality of Intercropped Corn and Lablab Bean

Low crude protein (CP) concentration in corn (Zea mays L.) silage is its major dietary limitation in dairy rations. In this experiment, four densities of corn (20,000, 40,000, 60,000, and 80,000 plants ha−1) and four densities of lablab bean [Lablab purpureus (L.) Sweet] (0, 40,000, 80,000, 120,000 plants ha−1) were intercropped to determine the optimal planting density in terms of forage yield, nutritive value, estimated milk production, and forage nutrient value. Experiments were conducted near Arlington and Lancaster, WI. Corn was sown in late April and lablab bean was sown in rows 8 cm beside corn rows 2 wk after corn planting. Averaged over locations, forage dry matter (DM) yield ranged from 11 Mg ha−1 to 20 Mg ha−1 as corn plant density increased from 20,000 to 80,000 plants ha−1 Lablab bean increased CP concentration by 22 g kg−1 DM between corn densities of 80,000 plants ha−1 and 20,000 plants ha−1 at a bean density of 120,000 plants ha−1 Calculated milk ha−1 values ranged from 17,500 kg ha−1 to 34,400 kg ha−1 as corn plant density increased from 20,000 to 80,000 plants ha−1 This experiment does not show benefit to addition of lablab bean into high producing corn stands. Corn sown at a density of 80,000 plants ha−1 and 0 bean plants ha−1 is recommended to maximize forage DM yield, milk ha−1, and crop value. Alternatively, addition of lablab bean into low density corn stands did increase CP concentration and feed nutrient value of the forage.

Relationship between P and N Concentrations in Corn

Tools to diagnose P crop status are becoming increasingly important to minimize the risk of surface and groundwater contamination from excessive fertilization while still applying sufficient P to optimize crop yield. The objectives of this study were to establish the relationship between P and N concentrations of corn (Zea mays L.) during the growing season and, in particular, to determine the critical P concentration required to diagnose P deficiency. Shoot biomass and P and N concentrations were determined weekly in an experiment with four to six N rates conducted over 2 yr (2004 and 2005) at three sites with adequate soil P for growth. The P and N concentrations decreased with time and increasing shoot biomass at all sites. The P concentration in relation to N under nonlimiting N conditions is described by a linear relationship (P = 1.00 + 0.094N, R2 = 0.76, P &lt; 0.001, n = 71) in which the concentrations are expressed in g kg−1 dry matter (DM). Under limiting N conditions, the relationship was different with greater P concentrations for a given N concentration. The present study establishes a predictive model for critical P concentration in corn shoots, as a function of the N concentration in the shoot biomass and the degree of N deficiency. This critical P concentration can then be used to quantify the degree of P deficiency during the current growing season.

Effect of Liming on the Plant Availability and Distribution of Zinc and Copper among Soil Fractions

Information on the redistribution of applied micronutrients into different fractions as a result of lime application is important to predict plant accumulation of nutrients and to select appropriate chemical extraction procedures for evaluation of micronutrient availability. The present work was carried out to study the influence of liming on the availability and redistribution of zinc (Zn) and copper (Cu) among soil fractions. Additionally, the effect of liming was evaluated on the recovery of these micronutrients by different chemical extractants (Mehlich‐1, Mehlich‐3, and diethylenetriaminepentaacetate (DTPA), which were correlated with Zn and Cu concentrations in corn (Zea mays L.) plants and soil fractions (exchangeable, organic matter, amorphous iron oxides, and crystalline iron oxides). The results showed that Zn added to soil samples that did not receive lime was retained mainly in the exchangeable and organic matter fractions. The liming resulted in distribution of Zn into iron oxides and as a result decreased the plant accumulation of Zn. Mehlich‐3 was the most efficient extractant to predict the plant accumulation of Zn in the acid soils, whereas DTPA was the most efficient in the limed soils. The oxide crystalline fraction was the major fraction responsible for retaining Cu in the soils. However, Cu added to soil was distributed mainly into organic matter. Mehlich‐3 was the most suitable extractant for predicting the bioavailability of Cu in limed or unlimed soils.

Grain Yield and Mineral Element Composition of Maize Grown on High Phosphorus Soils Amended with Water Treatment Residual

ABSTRACT The potential for phosphorus (P) movement from poultry-litter amended soils into surface waters heightens the need to manage elevated P concentrations. Amending high P soils with aluminum (Al) rich drinking water treatment residue in a greenhouse study reduced water extractable P levels and induced P deficiency in container grown wheat. Objectives of the current investigation were to determine the effect of water treatment residue on grain yield, leaf and grain mineral nutrient concentrations in corn (Zea mays L.) grown under field conditions and to examine pH, water and Mehlich 3-extractable P, and 0.01 M calcium chloride extractable Al in the amended soils at two sites. Poultry litter was amended with 0, 5.6, and 11.2 Mg ha− 1 of water treatment residual and applied to two sites prior to planting with corn in 1998. Additional rates (16.8 and 33.6 Mg ha− 1) of water treatment residue were applied directly to half of each plot on site I in 1999. Results indicated that water treatment residue application did not adversely affect corn grain yields or alter concentrations of mineral nutrients in leaves and grain. Water and Mehlich 3-extractable P and calcium chloride extractable Al concentrations were unchanged with water treatment residue applications in both years on both sites. Further studies are needed concerning optimal annual dosages and long term loading rates for direct soil application of water treatment residue to reduce soluble phosphorus.

Impact of Bt corn on the diplopod Allajulus latestriatus

Summary The application of transgenic crops has expanded enormously since their introduction to agriculture in the 1990s. Despite increased research activity in the area of non-target effects, the impact on many groups of soil organisms still remains unclear. In this study, laboratory feeding experiments were conducted to detect possible effects of Bt corn on the detritophagous Allajulus latestriatus (Diplopoda, Julidae). We tested the transgenic corn N4640Bt (expressing the Bt protein Cry1Ab), the corresponding non-transgenic isoline, and two further conventional corn varieties. Furthermore, a toxicity test was performed, in which purified Cry1Ab was added to a corn leaf diet in different concentrations. Cry1Ab concentrations in corn leaves, corn leaf diet, faeces and diplopods were quantified, applying an enzyme-linked immunosorbent assay (ELISA). We performed bioassays using the European Corn Borer Ostrinia nubilalis to test the insecticidal activity of different samples. No significant differences in mortality, consumption of corn leaves, or weight gain were found when animals were fed on N4640Bt compared to its isoline and the other two varieties. However, faeces production per diplopod was significantly increased when animals were kept on Bt corn compared to the isoline and to another corn variety. In the toxicity test, no significant differences were found for mortality, consumption, weight gain or faeces production between diets, not even at Cry1Ab concentrations more than 100 times higher than in Bt leaves. Bioassays proved that the Bt protein in transgenic leaves and in faeces of diplopods was still insecticidal. The toxicity test indicated that Cry1Ab excretion in the faeces is linearly correlated to the Cry1Ab uptake through the diet. Our findings suggest that Bt corn and Cry1Ab will not harm A. latestriatus . However, this diplopod excretes considerable amounts of Bt protein with its faeces. The Bt protein is still insecticidally active and, thus, becomes available to other soil organisms.

Efeito de aplicações de lodos de esgoto sobre os teores de metais pesados em folhas e grãos de milho

O lodo de esgoto é uma fonte importante de nutrientes para as culturas; contudo, os teores de metais pesados em sua constituição podem limitar seu uso em solos agrícolas. O objetivo deste estudo foi avaliar o efeito de doses de lodos de esgoto oriundos das Estações de Tratamento de Esgoto de Barueri (LB) e de Franca (LF), SP, sobre os teores de metais pesados em folhas e grãos de milho. O experimento foi realizado no Campo Experimental da Embrapa Meio Ambiente, em Jaguariúna (SP), no período de 1999 a 2001. Foram realizados três cultivos sucessivos de milho, com os seguintes tratamentos: testemunha absoluta; adubação mineral (NPK) recomendada para a cultura do milho, lodo de esgoto com base no teor de N para fornecer uma, duas, quatro e oito vezes a dose de N da adubação mineral. Avaliaram-se os teores totais (digestão nítrico-perclórica) de Cu, Mn, Ni, Pb e Zn em folhas e grãos de milho. A aplicação sucessiva dos lodos de esgoto acarretou aumento nos teores de Mn e Zn em folhas e grãos de milho. Em relação ao tratamento testemunha, a aplicação da dose mais elevada do LB (8LB) promoveu um incremento de até 270 e 625 % e de 35 e 115 % nos teores de Mn e Zn, respectivamente, nas folhas e grãos de milho. As folhas apresentaram maiores teores de metais pesados do que os grãos, o que envolve maior possibilidade de transferência de metais para a cadeia alimentar, caso essa parte da planta seja consumida. Essa elevação nos teores de metais pesados em folhas e grãos de milho, até à terceira aplicação dos lodos, não foi suficiente para atingir os níveis considerados fitotóxicos para o milho, tampouco para inviabilizar o uso dos grãos para o consumo humano.

EDTA-Enhanced Phytoremediation of Lead-Contaminated Soil by Corn

ABSTRACT EDTA-enhanced phytoremediation by corn (Zea mays L.) of soil supplemented with 500 mg L−1 lead (Pb) was examined. The chelate EDTA was used in order to increase Pb bioavailability at four levels: 0 (control), 0.5 (low), 1.0 (medium), and 2.5 mmol kg−1 (high). Plants were grown under controlled conditions in a growth-chamber with supplementary light. An EDTA concentration of 5.0 mmol kg−1 was lethal to plants. At high and medium EDTA levels plants grew significantly less than control ones. Lead concentrations in corn leaves increased with increased EDTA levels. Plants subjected to medium EDTA level had the greatest root to shoot Pb translocation. Plants subjected to high EDTA level showed high phosphorus (P) uptake and translocation within plants. Therefore, possibly it was not only Pb that caused toxic effect on plants, but also the high internal concentration of P that in turn could have complexed active Fe.

Influence of Planting Date on Aflatoxin Accumulation in Bt, non‐Bt, and Tropical non‐Bt Hybrids

Aflatoxin, produced by the fungus Aspergillus flavus Link, reduces the value of corn (Zea mays L.) and is usually associated with high temperatures, water stress, and insect damage. The objective of this study was to determine if Bt (Bacillus thuringiensis) corn hybrids or “tropical” germplasm could reduce aflatoxin accumulation with later planting dates. Aflatoxin accumulation (B1, B2, G1, and G2) in corn grain was evaluated on Bt, non‐Bt, and tropical non‐Bt hybrids and four planting dates (March, April, May, and June) from 1998 to 2000. Aflatoxin concentration in corn varied across years but generally decreased with later planting date. In 1998, aflatoxin accumulation was lower in Bt (314 ng g−1) than non‐Bt hybrids (634 ng g−1) but not different than tropical non‐Bt hybrid (470 ng g−1). However, aflatoxin contamination was lower from Bt hybrids (70 ng g−1) than from the tropical non‐Bt hybrid (259 ng g−1) but not different in non‐Bt hybrids (86 ng g−1) in 1999. In 2000, aflatoxin levels were low, and hybrid had no effect on aflatoxin concentration. Temperature and irrigation effects on aflatoxin accumulation were not consistent. Increased temperature and delayed harvest may lead to aflatoxin accumulation before harvest. However, precipitation may influence aflatoxin levels in some years. The results of this study indicate that aflatoxin accumulation in corn may be decreased with later planting date, and less accumulation in Bt than non‐Bt or tropical non‐Bt hybrids may be indirectly explained by insect reductions.

Trace Element Concentrations in Soil, Corn Leaves, and Grain after Cessation of Biosolids Applications

From 1974 to 1984, 543 Mg ha(-1) of biosolids were applied to portions of a land-reclamation site in Fulton County, IL. Soil organic C increased to 5.1% then decreased significantly (p < 0.01) to 3.8% following cessation of biosolids applications (1985-1997). Metal concentrations in amended soils (1995-1997) were not significantly different (p > 0.05) (Ni and Zn) or were significantly lower (p < 0.05) (6.4% for Cd and 8.4% for Cu) than concentrations from 1985-1987. For the same biosolids-amended fields, metal concentrations in corn (Zea mays L.) either remained the same (p > 0.05, grain Cu and Zn) or decreased (p < 0.05, grain Cd and Ni, leaf Cd, Cu, Ni, Zn) for plants grown in 1995-1997 compared with plants grown immediately following termination of biosolids applications (1985-1987). Biosolids application increased (p < 0.05) Cd and Zn concentrations in grain compared with unamended fields (0.01 to 0.10 mg kg(-1) for Cd and 23 to 28 mg kg(-1) for Zn) but had no effect (p > 0.05) on grain Ni concentrations. Biosolids reduced (p < 0.05) Cu concentration in grain compared with grain from unamended fields (1.9 to 1.5 mg kg(-1)). Biosolids increased (p < 0.05) Cd, Ni, and Zn concentrations in leaves compared with unamended fields (0.3 to 5.6 mg kg(-1) for Cd, 0.2 to 0.5 mg kg(-1) for Ni, and 32 to 87 mg kg(-1) for Zn), but had no significant effect (p > 0.05) on leaf Cu concentrations. Based on results from this field study, USEPA's Part 503 risk model overpredicted transfer of these metals from biosolids-amended soil to corn.

Simulation of nitrogen rhizodeposition and assimilation back into corn (Z ea mays L.) roots

The objectives were to quantify the dynamics of N exchange between corn root and soil under field conditions and to compute the amount of N-rhizodeposition that is recycled back into corn by maturity. In a previous publication the simulation model NCSWAP/NCSOIL was used to quantify the release of organic-C from corn and its incorporation into soil organic matter. In this publication, results from the same simulations but pertinent to N are presented. The model was calibrated against measured N concentration in corn and soil and 15N enrichment data obtained from a long-term field experiment located near St Paul, MN. Field management included rototillage, the removal of stover-residue and grain and 4 fertilizer N treatments: 200 and 20 Kg N ha −1 added yearly from 1980 to 1992, with 15N added with the fertilizer from 1980 until either 1985 or 1992. The same total amount of 15N was added with the 200 and 20 Kg N ha −1 fertilizer: 4 and 40 15N at.%, respectively. Corn roots released 24% of total N uptake. This loss was mitigated by the recycling of 14% of N-rhizodeposition into corn by maturity. 15N enrichment in corn and soil was higher for the 200 than the 20 Kg N ha −1 treatment. This resulted from the rapid N mineralization–immobilization turnover that channelled N through the inorganic N pool whose 15N enrichment was fixed yearly to that of the fertilizer. Tracer N enrichment decreased more rapidly in corn than in soil from 1986 to 1992 when tracer N was no longer added with the fertilizer, and by 1992, 15N was localized in the stable pool and flushed from the more labile pools.

Alterações químicas do solo e resposta do milho à calagem e aplicação de gesso

A calagem e a aplicação de gesso levam a modificações químicas no solo que podem influenciar o crescimento radicular e a produção de culturas anuais. Com o objetivo de avaliar as alterações químicas do solo e a resposta do milho ao calcário e gesso aplicados no sistema plantio direto, foi realizado um experimento em um Latossolo Vermelho distrófico textura argilosa, em Ponta Grossa (PR). Os tratamentos, dispostos em blocos completos ao acaso em parcelas subdivididas com três repetições, constaram da aplicação de calcário dolomítico (sem calcário e 4,5 t ha-1 de calcário na superfície, em dose total e 1/3 da dose por ano, durante três anos, e incorporado), nas parcelas, e doses de gesso (0, 3, 6 e 9 t ha-1), nas subparcelas. Os tratamentos com calcário foram aplicados em julho e as doses de gesso em outubro de 1998. A cultura do milho foi avaliada no ano agrícola de 2001/02. A correção da acidez pela calagem na superfície, com ou sem parcelamento, foi mais acentuada na camada superficial do solo (0-0,05 m) e houve maior reação nas profundidades de 0,05-0,10 e 0,10-0,20 m, quando o calcário foi incorporado. O gesso melhorou o subsolo, aumentando os teores de Ca e S-SO4(2-), aumentou a concentração de N, K e Ca no tecido foliar do milho e causou redução do Mg no solo e nas folhas. O crescimento radicular do milho não foi influenciado pelos tratamentos de calcário e gesso. A calagem na superfície, com ou sem parcelamento, ou com incorporação e a aplicação de gesso aumentaram a produção de milho, em decorrência do aumento da saturação por Ca nas camadas superficiais do solo. A aplicação de gesso agrícola, associada à calagem, foi uma estratégia eficiente para maximizar a produção de milho.

Rheology of starch–milk–sugar systems: effect of heating temperature

This study aims to investigate the effect of heating temperature on the rheological behavior of starch–milk–sugar (SMS) pastes. Different concentrations of corn and wheat starch were heated in liquid skim milk containing 8 wt% sugar at 60, 75, 85 and 95 °C. The sugars used are glucose, sucrose and fructose. The pastes heated at 60 and 75 °C show the same low value of viscosity. As the heating temperature increased to 95 °C, a great increase in the apparent viscosity of the paste was observed. This means that the degree of gelatinization of starch heated at 60 and 75 °C was insignificant. On the other hand, the pastes exhibited a time-independent behavior at low heating temperature (60 and 75 °C) and changed to a thixotropic behavior with increasing the heating temperature. One exception was the 2 wt% wheat–milk–glucose paste, which shows an antithixotropic behavior. The Herschel–Bulkley model was used to fit the flow curves of SMS pastes. The yield stress and the consistency coefficient increased with increasing the heating temperature and starch concentration, reflecting the increase in paste viscosity.

Determination of total arsenic levels by hydride generation atomic absorption spectrometry in foods from south-east Spain: estimation of daily dietary intake

The total concentration of arsenic in different foods from south-east Spain was determined by hydride generation atomic absorption spectrometry. Mineralization was carried out with an HNO3-HClO4 mixture in a thermostated sand bath. Arsenic determination was performed by the standard addition method. Analyses of NIST and CBR-CEC reference materials demonstrated the reliability and accuracy of the technique. The highest arsenic levels were found in seafood, cereals, meat and meat by-products. In meat and meat by-products, the total arsenic measured in meat was significantly higher than that in sausages (p<0.05). In cereals, arsenic concentrations in corn and white rice samples were significantly higher (p<0.01) than those measured in wheat by-products. Mean arsenic concentrations in cheese were statistically lower than those in other dairy products (p<0.01). New data have been provided on the total arsenic content of a variety of foods in Spain, which is important for making exposure estimates. The estimated daily intake of total arsenic in the Spanish diet was 221 μg As day−1.

Quantifying nitrogen status of corn ( Zea mays L.) in the field by reflectance measurements

Nutrient deficiencies can seriously reduce yield and economic returns to farmers. Tools that can rapidly quantify the nutritional status of plants are needed for efficient fertilizer management. Reflectance measurements have shown to be a useful tool to identify the nutritional status of different plant species. A set of calibration curves relating reflectance ratios to the nitrogen (N), phosphorus (P), magnesium (Mg), and iron (Fe) concentrations in corn leaves was established in greenhouse trials in a previous study. In this paper these calibrations were examined for their ability to identify nutrient deficiencies under field conditions. A 2-year field experiment was conducted to check and define the regions of the spectra that are influenced by leaf N concentration and to set up possible equations for quantifying the leaf N status in the field. The experiment was carried out on a loess derived soil in south-western Germany. Reflectance of corn leaves, from plants grown with six different N fertilization treatments ranging from 0 to 160 N kg ha −1, was determined once a week from the beginning of June until the end of July. Reflectance measurements were performed at the 4th leaf of corn plants with a digital LEICA S1 Pro camera under controlled light conditions. Reflectance was measured in different wavelength ranges in the visible and infrared spectra. Leaf scans were evaluated within the L*a*b*-color system. Total N concentration of corn leaves was determined chemically and correlated with reflectance patterns. Significant correlations between corn N status and leaf reflectance changes were obtained at a nitrogen level of N<3.0%. Reflectance patterns at 510 780, 516 1300, 540 1300 nm were found most suitable to the corn N status in the field regardless of the year or sampling date. The results indicate that the spectral patterns and the defined calibration curves of N deficiency from greenhouse studies could be used in field studies. Thus, reflectance measurements may serve as a rapid, non-destructive approach to discriminate nitrogen deficiency in the field.

RELATIVE AVAILABILITY COEFFICIENTS OF ORGANIC AND INORGANIC Zn FERTILIZERS

Zinc sulfate (ZnSO4) has traditionally been the “reliable” source of Zn fertilizer but other sources of Zn are also available. Some are derived from industrial by-products, varying from flue dust reacted with sulfuric acid to organic compounds derived from the paper industry. The degree of Zn availability in Zn sources derived from these various by-products is related to the manufacturing process, the source of complexing or chelating agents (organic sources), and the original product used as the Zn source. Many claims are made regarding the relative efficiency of traditional inorganic Zn fertilizers and complexed Zn sources. The objective of this greenhouse study was to determine the availability coefficients of several commercial Zn fertilizer materials (organic and inorganic) that are commonly used to correct Zn deficiencies in soils. We evaluated the dry matter production, total Zn uptake, and Zn concentration in corn (Zea mays L. cv. P3752) plants fertilized with six different commercial Zn fertilizers. The sources included three granular inorganic Zn sources, two granular organically complexed Zn sources, and liquid ZnEDTA. The soil was low in available Zn (AB-DTPA Zn = 0.48 mg kg−1) and limed to a pH of 7.2. The Zn fertilizers were added to 5 kg pots at rates equivalent to 0, 0.21, 0.42, 0.84, 1.68, and 3.36 mg Zn kg−1 of soil. A relative availability coefficient (RAC) was used to determine the relative availability of all sources. The RAC is determined by comparing the slopes of the regression lines of each measured parameter with the slope of the reference material. The ZnLignosulfonate, ZnSO4, and ZnEDTA were always the most effective material in supplying the plant's needs. The RAC of these three materials ranged from 70 to 100%, depending on plant parameter measured. The ZnOxysulfate, with 55% water-solubility, also performed well with a RAC from 48 to 69%. The lower water-soluble materials (ZnOxysulfate, 26% water-soluble, and ZnSucrate, 1% water-soluble) were least effective with RAC values ranging from −12 to 25%. When comparing all sources, water-solubility was the primary factor governing the performance of Zn fertilizers. High water-solubility is required if a Zn fertilizer is going to be effective in meeting the plant's Zn needs. Zinc ions that are reacted with an organic complexing agent do not guarantee the resulting fertilizer will perform like a true chelate and have high plant availability. If the end product is not highly water-soluble, it will be very inefficient in supplying Zn to the plant. These results confirm our previous research where we concluded that a Zn fertilizer must be from 50% water-soluble to be an effective Zn source.

Translocação de zinco e crescimento radicular em milho

Alguns problemas de crescimento radicular de plantas de milho têm sido atribuídos a deficiência de Zn, em virtude de sua pouca mobilidade na planta. Foi realizado um experimento em casa de vegetação em 1997/98, em Botucatu (SP), para avaliar a translocação de zinco para as raízes do milho (Zea mays ), quando aplicado via radicular e foliar, assim como o efeito do Zn no crescimento das raízes. Foram utilizados vasos de 2,5 L, com solução nutritiva que continha de 0,0 a 2,0 µmol L-1 de Zn, com e sem aplicação semanal via foliar. O experimento foi colhido 40 dias após a emergência. A produção de matéria seca da parte aérea e raízes, bem como o comprimento, o diâmetro e a superfície radiculares, não foram influenciados pelos tratamentos. A translocação do nutriente aplicado às folhas para as raízes ocorreu em maior intensidade quando os teores foliares estavam na faixa de suficiência do nutriente. O sistema radicular do milho mostrou-se pouco sensível à deficiência de Zn, uma vez que o crescimento foi normal, mesmo quando as raízes apresentavam teores de Zn da ordem de 7 mg kg-1.

191 Use of the Minolta SPAD-502 to Determine Chlorophyll Concentration in Ficus benjamina L. and Populus deltoides Marsh Leaf Tissue

The Minolta SPAD meter has been used to evaluate chlorophyll concentration in plant material to provide an inexpensive method to collect rapid, nondestructive data. Correlations of SPAD data and chlorophyll concentrations in corn have been very accurate r2 = 0.95), and can be used to monitor plant nutrient status as a function of chlorophyll concentration. There has been evidence that the calibrated accuracy of the SPAD meter is diminished at low and high concentrations of chlorophyll. Our study attempted to build the same type of background information for two tree species for use in evaluating plant response in experimental media experiments. Ficus benjamina L. and Populus deltoides Marsh were grown in containers of varied media. Leaf tissue was measured with a Minolta SPAD-502, and the tissue was then removed and processed with N,N-dimenthylformamide for analysis in a spectrophotometer. The remainder of the leaf sample was analyzed in an ICAP for tissue nutrient levels. Data were analyzed to evaluate the usefulness of the SPAD meter for woody plant leaf tissue evaluation and to develop calibration curves for use in future studies. There was a positive correlation (r2 = 0.943 in Ficus) between SPAD data and combined concentrations of chlorophyll a and b. Accuracy of the SPAD data was diminished when chlorophyll concentrations were low (SPAD &lt;20, chorophyll &lt;450 μg·mL-1) and high (SPAD &gt;45, chorophyll &gt;1350 μg·mL-1)..