Techniques of iron addition to a sewage effluent based nutrient film system for growing tomatoes

The use of the nutrient film technique for growth of crops in sewage effluent has demonstrated the need to provide an iron supplement to the plants. Work at Portsmouth Polytechnic has studied several techniques by which iron may be added to the plant root block and also to the plant leaves. The results of the studies show clearly that one technique is particularly successful. Plants grown using this method can produce crop yield comparable with commercial practice.     

Cultivar differences for tolerance to Fe and Zn deficiency: A comparison of two maize hybrids and their parents

The Fe and Zn deficiency tolerances for two high yielding maize (Zea mays L.) hybrids (G‐2 and G‐5) and their parent cultivars were examined by growing them in nutrient solutions. The results indicated the occurrence of heterosis for Zn deficiency tolerance in G‐5, and to a lesser extent in G‐2. Each cultivar was susceptible to Fe deficiency and did not show signs of recovery from chlorosis. The symptoms of Fe deficiency were distinct from those for Zn deficiency. Plant growth was affected more by Fe deficiency than by Zn deficiency. The roots of cultivars were reduced in growth under Fe deficiency conditions.     

Manganese toxicity in bush bean as affected by concentration of manganese and iron in the nutrient solution

An experiment was conducted to clarify the relationship between Mn toxicity and Fe deficiency in bush snap bean (Phaseolus vulgaris L. cv. ‘Wonder Crop No. 2'). Seedlings were grown in full strength Hoagland No. 2 solution at pH 6.0 for ten days. Six concentrations of Mn as MnCl₂.4H₂O were used in combination with three concentrations of Fe as FeEDTA.

Toxicity symptoms, induced by low levels of Mn (0.1 ppm and above), included: small brown necrotic spots and veinal necrosis on primary leaves; necrosis on primary leaf petioles; interveinal chlorosis, with or without brown necrotic spots, on trifoliate leaves; and brown necrotic spots on stipules. Manganese toxicity symptoms were alleviated or prevented by increasing Fe concentration in the nutrient solution.

Manganese concentration in the leaves increased with increasing Mn and decreased with increasing Fe concentration in the nutrient solution, Iron concentration in the roots increased with increasing Fe concentration in the nutrient solution; however, Fe concentration in the leaves was not significantly affected by increasing Mn concentration in the solution culture. Manganese toxicity symptoms developed when Mn concentration in the leaves reached about 120 ppm.

A decrease in the Fe/Mn ratio in the nutrient solution resulted in a proportionate decrease in that of the leaves. Manganese toxicity symptoms occurred when the Fe/Mn ratio in the solution was 10.0 and below, or when the ratio in the leaves was less than 1.5. The ratio of Fe/Mn in the solution required for optimum growth of ‘Wonder Crop No. 2’ bean, without Mn toxicity symptoms, was in the range of 20.0 to 25.0.

Results indicate that the chlorosis on bush bean leaves induced by excessive Mn in the nutrient solution was due to excessive accumulation of Mn and not to Fe deficiency.     

Micronutrient deficiencies and toxicities of cassava plants grown in nutrient solutions. I. Critical tissue concentrations

The programmed nutrient addition technique was used in a series of 5 experiments to determine the response in growth and micronutrient content of cassava (Manihot esaulenta Crantz) cv. M Aus 10, to 8 supply levels of boron, copper, iron, manganese and zinc respectively. The experiments were of 9 weeks duration and utilized 22 litre pots of nutrient solution. The supply levels for each micronutrient covered the range from severe deficiency to toxicity. Critical tissue concentrations for deficiencies determined by relating total dry matter production to the nutrient concentration in the youngest fully expanded leaf blades were (μg/g): boron 35, copper 6, manganese 50, and zinc 30. Likewise, critical concentrations for toxicities in the same index tissue were (μg/g): boron 100, copper 15, manganese 250, and zinc 120. In the iron experiment, the data were too variable to allow precise determination of critical concentrations for deficiency and toxicity. Critical micronutrient concentrations in the petioles of the youngest fully expanded leaves were also determined, but offered no advantage over the leaf blades.     

Effect of sulfur deficiency and excess on yield and sulfur accumulation in tomato plants

Abstract

Tomato (Lycopersicon esculentum Mill. var. hybrid 6C‐204) plants were grown for 95 days after germination until each one bore 6 ripe clusters in a greenhouse using nutrient solutions with nine added sulfate levels ranging from 0 to 105 me/1.

Sulfur‐deficiency symptoms and characteristics of plants growing under hign SO₄‐S levels were observed and described. Fruit yields were negatively affected by both S‐deficiency and high SO₄‐S concentrations. Top growth was affected more than root growth by changes in the amount of SO₄‐S supplied. The critical SO₄‐S concentration in the growth media ranged from 2 a 22.5 me/1.

Leaf sulfate‐S increased gradually in leaves and roots as SO₄‐S supply in the nutrient solution increased while organic‐S remained relatively constant. Leaf sulfate‐S critical value was growth stage dependent. Maximum yields at flowering were associated with leaf concentrations of 0.48–1.2% SO₄‐S and 0.25–0.35% organic‐S.     

Differences in Response to Iron Deficiency Among Some Lines of Common Bean

Abstract

Five dry bean cultivars (Coco blanc, Striker, ARA14, SVM29‐21, and BAT477) were evaluated for their resistance to iron deficiency on the basis of chlorosis symptoms, plant growth, capacity to acidify the external medium and the root‐associated Fe³⁺‐reduction activity. Plants were grown in nutrient solution supplied or not with iron, 45 µM Fe(III)EDTA. For all cultivars, plants subjected to iron starvation exhibited Fe‐chlorosis. These symptoms were more severe and more precocious in BAT477 and Coco blanc than in the others cultivars. An important acidification of the culture medium was observed between the 4th and the 8th days of iron starvation in Striker, SVM29‐21 and, particularly, ARA14 plants. However, all Fe‐sufficient plants increased the nutrient solution pH. This capacity of acidification appeared more clearly when protons extrusion was measured in 10 mM KCl + 1 mM CaCl₂. The above genotypic differences were maintained: ARA14 showed the higher acidification followed by Coco blanc and BAT477. Iron deficiency led also to an increase of the root‐associated Fe(III)‐reductase activity in all lines. However, genotypic differences were observed: Striker shows the highest capacity of iron reduction under Fe deficiency condition.     

Interaction of Different Iron Chelates with an Alkaline and Calcareous Soil: A Complementary Methodology to Evaluate the Performance of Iron Compounds in the Correction of Iron Chlorosis

Abstract

A great number of studies have shown that the stability of iron chelates as a function of pH is not the unique parameter that must be considered in order to evaluate the potential effectiveness of Fe‐chelates to correct iron chlorosis in plants cultivated in alkaline and calcareous soils. In fact, other factors, such as soil sorption on soil components or the competition among Fe and other metallic cations for the chelating agent in soil solution, have a considerable influence on the capacity of iron chelates to maintain iron in soil solution available to plants. In this context, the aim of this work is to study the variation in concentration of the main iron chelates employed by farmers under field conditions—Fe‐EDDHA (HA), Fe‐EDDHMA (MA), Fe‐EDDHSA (SA), Fe‐EDDCHA (CA), Fe‐EDTA (EDTA), and Fe‐DTPA (DTPA)—in the soil solution of a calcareous soil over time. To this end, soil incubations were carried out using a soil:Fe solution ratio corresponding to soil field capacity, at a temperature of 23°C. The soil used in the experiments was a calcareous soil with a very low organic matter content. The variation in concentration of Fe and Fe‐chelates in soil solution over time were obtained by measuring the evolution in soil solution of both the concentration of total Fe (measured by AAS), and the concentration of the ortho‐ortho isomers for Fe‐EDDHA and analogs or chelated Fe for Fe‐EDTA and Fe‐DTPA (measured by HPLC). The following chelate samples were used: a HA standard prepared in the laboratory and samples of HA, MA, SA, CA, Fe‐EDTA, and Fe‐DTPA obtained from commercial formulations present in the market. The percentage of iron chelated as ortho‐ortho isomers for HAs was: HA standard (100%); HA (51.78%); MA (60.06%); SA (22.50%); and CA (27.28%). In the case of Fe‐EDTA and Fe‐DTPA the percentages of chelated iron were 96.09 and 99.12, respectively. Results show that it is possible to classify the potential effectiveness of the different types of iron chelates used in our experiments as a function of two practical approaches: (i) considering the variation of total iron in soil solution over time, MA is the best performing product, followed by HA, CA, SA, DTPA, EDTA, and ferrous sulfate in the order listed and (ii) considering the capacity of the different iron chelates to maintain the fraction of chelated iron (ortho‐ortho isomers for HA, MA, SA, and CA and total chelated iron for EDTA and DTPA) in soil solution, the order is: SA > CA > HA > MA > EDTA ≈ DTPA. This result, that is related to the nature of the chelate and does not depend on the degree of chelated Fe in the products, indicates that SA and CA might be very efficient products to correct iron chlorosis. Finally, our results also indicate the suitability of this soil incubation methodology to evaluate the potential efficiency of iron compounds to correct iron chlorosis.     

Iron Toxicity in Wetland Rice and the Role of Other Nutrients

Abstract

Iron (Fe) toxicity is a widespread nutrient disorder of wetland rice grown on acid sulfate soils, Ultisols, and sandy soils with a low cation exchange capacity, moderate to high acidity, and active Fe (easily reducible Fe) and low to moderately high in organic matter. Iron toxicity reduces rice yields by 12–100%, depending on the Fe tolerance of the genotype, intensity of Fe toxicity stress, and soil fertility status. Iron toxicity can be reduced by using Fe-tolerant rice genotypes and through soil, water, and nutrient management practices. This article critically assesses the recent literature on Fe toxicity, with emphasis on the role of other plant nutrients, in the occurrence of and tolerance to Fe toxicity in lowland rice and puts this information in perspective for future research needs. The article emphasizes the need for research to provide knowledge that would be used for increasing rice production on Fe-toxic wetlands on a sustainable basis by integration of genetic tolerance to Fe toxicity with soil, water, and nutrient management.     

Grapevine Growth and Physiological Responses to Iron Deficiency

ABSTRACT

Iron (Fe) deficiency is one of the major abiotic stresses affecting fruit tree crops growing in calcareous soils in the Mediterranean region. A better understanding of changes in the growth and physiological characteristics of grapevine plants during the development of Fe deficiency will help to improve Fe fertilizer management recommendations. An experiment was conducted in field conditions to determine the effects of Fe deficiency during vegetative growth on leaf photosynthesis, dry matter accumulation, pigments, and other physiological parameters. Iron deficiency considerably decreased leaf net photosynthetic rate, leaf area, and dry matter accumulation. Depressed photosynthesis and plant growth resulted in increased fruit abscission and changes in dry matter among plant tissues. The results help explain the effects of Fe deficiency on suppression of grapevine growth and yield and provide information for improving the diagnosis of Fe deficiency in grapevine production.     

邻啡罗啉比色法测定土壤中有效铁的条件优化

采用DTPA溶液浸提-邻菲罗啉比色法测定土壤中有效铁的含量,探讨了此方法的最佳实验条件.结果表明,以邻菲罗啉为显色剂,可在510nm处测定土壤中有效铁的含量;最适试剂用量为:每5ml待测液加入100 g/L的盐酸羟胺l ml,100 g/L的醋酸胺8 ml,100 g/L的邻菲罗啉显色剂10ml;待测液显色最适条件为温度在60℃下显色30 min;优化后的测定方法相对标准偏差RSD＜2.0％,回收率98.6％～ 100.2％.此法操作简便、灵敏度高、显色稳定、回收率高,适用于测定微碱性或碱性土壤中有效铁的含量.