Growth and composition of cabbage as affected by nitrogen nutrition

Abstract

The effect of cultivar and rate of N application on nitrate accumulation in cabbage (Brassica oleracea capitata, L.) was investigated in a field study. At harvest, significant differences in nitrate accumulation among cultivars occurred, with the greatest differences occurring at the highest rate of N applied, 450 kg N/ha. Two of three straight‐leaved varieties, Market Prize and Market Victor, accumulated more nitrate than three savoy‐leaved varieties, Savoy Ace, Savoy King, and Chieftain Savoy. The third straight‐leaved variety studied, Harris Resistant Danish, accumulated the least nitrate. Pattern of nitrate accumulation was closely correlated with date of maturity, with the earliest‐maturing variety, Market Victor, accumulating the highest levels of nitrate, and the latest‐maturing variety, Harris Resistant Danish, accumulating the least nitrate. For all six varieties, outer wrapper‐leaf samples showed higher nitrate levels than head samples.

In a second study, the effect of cultivar, N source, and nitrapyrin on yield and nutritional status of cabbage was studied under greenhouse conditions. The six cabbage cultivars showed no significant differences in nitrate accumulation after 65 days. The presence of 10 ppm of nitrapyrin, 2‐chloro‐6‐(trichloromethyl) pyridine, resulted in a restriction in fresh and dry weight production in cabbage. No visual, foliar symptoms of nitrapyrin toxicity were evident. Calcium levels were reduced in the presence of nitrapyrin regardless of N source. Adding nitrapyrin had no sign:ficant effect on Mg concentration, and highest Mg levels occurred under ammonium nutrition. Potassium levels were increased in the presence of nitrapyrin when the soil was not supplemented with K, whereas differences in K content due to the inhibitor were insignificant when KNO₃ was supplied.     

Chlorophyll meter readings in corn as affected by plant spacing

Abstract

Heightened environmental consciousness has increased the perceived need to improve nitrogen (N) use efficiency by crops. Synchronizing fertilizer N availability with maximum crop N uptake has been proposed as a way to improve N‐use efficiency and protect ground water quality. Chlorophyll meters (Minolta SPAD 502) have the potential to conveniently evaluate the N status of corn (Zea mays L.) and help improve N management. A potential problem with the use of chlorophyll meters is the effect of within‐row plant spacing on meter reading variability. Chlorophyll meter readings and leaf N concentration of irrigated corn at anthesis and grain yield at harvest were measured on plants grouped into eight within‐row plant spacing categories. Leaf N concentration was not affected by plant spacings, but chlorophyll meter readings and grain yield per plant increased as plant competition decreased and N fertilizer rate increased. These data indicate that avoiding plants having extreme spacings can greatly increase precision when using chlorophyll meters to evaluate the N status of corn.     

Biomass production and phosphorus accumulation of potato as affected by phosphorus nutrition

Potato (Solatium tuberosum) generally requires high amounts of phosphate fertilizer to reach economically acceptable yields, particularly in soils originating from volcanic ash. This is a consequence of the potato plants low root density and the slow soil diffusion rate of phosphorus (P) in these soils. Our objective was to evaluate the effect of P rates on tuber yield, biomass production, and distribution, biomass P accumulation and concentration, and P distribution in potato cv. Mexiquense. The experiment was carried out in an Andisol (7.8 μg g^‐1 Olsen‐P) located at the east of Valle de México. Fertilization rates were 0, 18,41,46,69,78,90,106,113,135,150,163, and 207 kg ha^‐1 P, from ordinary superphosphate. Top growth and root biomass, tuber yield, P percentage and P accumulation in different plant parts were measured at harvest. Minimum and maximum average tuber yields were 8.4 and 18.0 Mg ha^‐1; the plants absorbed 5.8 and 11.8 kg ha^‐1 P, corresponding to 0 (control) and 207 kg ha^‐1 P, respectively. Phosphorus fertilization had little influence on plant P concentration, where average concentrations in tuber and top growth were 0.20 and 0.24 % P, respectively. By contrast, P accumulation increased with increasing P rates, but P distribution between tuber and top growth was dependent on the amount of P applied. The control treatment showed approximately 1:1 distribution of P between top growth and tuber, but as P rate increased, top growth P decreased and tuber P increased. When applying the highest P rate, 36% of P accumulated in the top growth and 64 % in the tuber. The information obtained will permit decisions on the correct use of phosphate fertilizer for potato in Andisols of the Valle de Mexico.     

Root growth and mineral nutrition of corn hybrids as affected by phosphorus and lime

Abstract

The effects of triple superphosphate (TS) and liming on macronutrient accumulation and root growth of Pioneer 3072 and Cargill 505 corn hybrids were studied. Corn plants were grown up to 30 days in pots with 7 L of a dark red Latosol sandy loam (Haplortox). Lime was applied to raise base saturation to 30, 50, and 70%, in two levels of phosphorus (P) fertilization with TS (0 and 200 ppm P). There was an increase in root surface due to lime only in pots without TS, with no effects on plant growth or nutrition. Both corn hybrids responded to P fertilization, but Pioneer yielded more dry matter than Cargill. The roots of Cargill were thicker and, when in TS presence, were longer and had a larger surface than Pioneer. There was an increase in macronutrient uptake in the P fertilized pots. Pioneer required more nutrients and showed a higher efficiency in acquiring and utilizing the nutrients from the soil. A higher response of Pioneer in dry matter and nutrient acquisition was more related to the physiological efficiency than to root morphology.     

Elemental composition of the rice plant as affected by iron toxicity under field conditions

Abstract

Iron (Fe) toxicity is a major nutrient disorder affecting the production of wetland rice in the humid zone of West Africa. Little attention has been given to determining the macro‐ and micronutrient composition of rice plants grown on wetland soils where Fe toxicity is present although results from such study could provide useful information about the involvement of other nutrients in the occurrence of Fe toxicity. A field experiment was conducted in the 1997 dry season (January‐May) at an Fe toxic site in Korhogo, Ivory Coast, to determine the elemental composition of Fe tolerant (CK 4) and susceptible (Bouake 189) lowland rice varieties without and with application of nitrogen (N), phosphorus (P), potassium (K), and zinc (Zn). For both Fe‐tolerant and susceptible varieties, there were no differences in elemental composition of the whole plant rice tops, sampled at 30 and 60 days after transplanting rice seedlings, except for Fe. All the other nutrient element concentrations were adequate. Both Fe‐tolerant and susceptible cultivars had a high Fe content, well above the critical limit (300 mg Fe kg^‐1 plant dry wt). These results along with our observations on the elemental composition of rice plant samples collected from several wetland swamp soils with Fe toxicity in West Africa suggest that “real”; iron toxicity is a single nutrient (Fe) toxicity and not a multiple nutrient deficiency stress.     

Lettuce yield and root activity as affected by an ion exchange substrate and mineral nutrition level

The study involved investigating the effect of ion exchange substrate (IES) addition to a nutrient solution (2% or 5% v/v) on the yield and root parameters of butterhead lettuce (Lactuca sativa L. cv. “Justyna”) under the conditions of basic (1.5-times concentrated Hoagland solution, electrical conductivity, EC 2.41–2.47 dS m^?1), and intensive (3-times concentrated Hoagland solution, EC 6.85–7.30 dS m^?1) mineral nutrition level. Regardless of the mineral nutrition level, both experimental additions of IES significantly increased the yield and elevated the volume, as well as the whole (WRA) and the active (ARA) adsorptive surface area of roots. It was confirmed that the substrate did not cause salt stress. Additionally, it was revealed that the substrate constitutes a beneficial component of lettuce in non-salinized (basic) or salinized (intensive mineral nutrition level) environment and that the 2% dose was more favorable than 5% dose.     

Concentrations of nutrient elements in parts of siratro as affected by phosphorus supply and plant age

Abstract

The distribution of some nutrient elements in various parts of Siratro plants of different age and phosphorus status was examined in order to assess which plant parts were best to sample for chemical analysis of nutrient status and to estimate the relative mobility of these elements within the shoot.

With increasing physiological age of leaves, concentrations of nitrogen, phosphorus, sulphur and potassium decreased, concentrations of calcium, aluminium, manganese and boron increased and concentrations of magnesium, iron, zinc and copper were little affected. Concentrations of nitrogen, phosphorus, sulphur, calcium, aluminium, boron, zinc and copper in plant parts between the tip and the third youngest, expanded leaf changed little with plant age, suggesting that analysis of this portion of the shoot would be a suitable guide to the sufficiency, or otherwise, of these elements in Siratro plants. By contrast, potassium concentration in all plant parts was markedly depressed by increasing plant age, suggesting that a standardized sampling time would be necessary for interpretation of plant potassium status. Concentrations of magnesium, iron and manganese in all plant parts also decreased with plant age, but to a lesser extent than potassium.

Concentrations of all elements, except nitrogen and phosphorus, decreased slightly with increasing phosphorus supply. This decrease could best be attributed to a dilution of these elements with increased plant growth, induced by phosphorus.

The present results suggested that potassium, and possibly iron and magnesium, were redistributed in Siratro shoots with time whereas other elements were relatively immobile.     

Soil microbial metabolism and nutrient status in a Mediterranean area as affected by plant cover

The Mediterranean area of Southern Italy is characterized by different natural plant covers that mainly reflect different successional stages (i.e. low maquis, high maquis, Quercus ilex wood) and managed areas with introduced plant species (such as Pinus species). Soil properties could be affected by plant cover types as well as by plant species. Our objective was to determine the relationships of plant cover types and plant species with the chemical and biological characteristics of the soil. In four neighbouring areas with different plant cover types (low maquis, pure high maquis, high maquis with pines and pinewood, with pines planted by foresters in both cases), soil samples were collected under different plant species in order to evaluate the effect of plant cover types and plant species on soil properties. Soil samples were analyzed for nutrient content, microbial biomass, soil potential respiration and enzymatic activity (phosphatase, arylsulphatase, β-glucosidase and hydrolase activities) as well as for pH, water holding capacity (WHC) and cation exchange capacity (CEC). Application of cluster analysis and principal component analysis to the data revealed that the plant cover type was the key factor influencing soil properties more than plant species. In fact, the largest differences were observed between pure high maquis soils and all other soils, with pure high maquis soils generally showing the highest values of WHC, CEC, nutrient content, organic and microbial C, soil respiration, phosphatase, arylsulphatase and β-glucosidase activities. The significantly lower values of these variables in the low maquis relative to the pure high maquis probably reflect the effect of ecological succession on soil. The high maquis with pine, differing from the pure high maquis only for the presence or absence of pine, showed values of soil physical, chemical and biological characteristics similar to those found in the low maquis, thus suggesting that the presence of pine retards soil development.     

Cell membrane stability and leaf water relations as affected by phosphorus nutrition under water stress in maize

Abstract

A field experiment was conducted to investigate the effect of P nutrition under water stress on the cell membrane stability measured by the polyethylene glycol test, plant growth, and internal plant water relations in maize (Zea mays L.). Adaptation to water deficits with improved P nutrition was observed. The cell membrane stability increased, leaf water potential and osmotic potential decreased, and turgor potential increased with improved P nutrition. Osmoregulation was evident with improved P nutrition. Sugar and K were the major osmotic contributors. Total plant dry weight and relative growth rate increased with improved P nutrition under water stress, suggesting that the supply of extra P to plants may be beneficial to increase the tolerance to drought.     

Release of zinc mobilizing root exudates in different plant species as affected by zinc nutritional status

The effect of zinc nutritional status of the plant on the release of zinc mobilizing root exudates was studied in various dicotyledonous (apple, bean, cotton, sunflower, tomato) and graminaceous (barley, wheat) plant species grown in nutrient solutions. In all species, zinc deficiency increased root exudation of amino acids, sugars and phenolics. However, the root exudates of zinc deficient dicotyledonous species did not enhance zinc mobilization from a synthetic resin (Zn chelite), or a calcareous soil, although mobilization of iron from Fe^III hydroxide was increased. By contrast in the graminaceous species, root exudates from zinc deficient plants greatly increased mobilization of both zinc and iron from the various sources. These differences in capability of mobilization of zinc and iron between the plant species are the result of an enhanced release of phytosiderophores with zinc deficiency in the graminaceous species.     

Sequential fractionation and plant availability of heavy metals as affected by sewage sludge applications to soil

Abstract

The effect of sewage sludge applications on extractability and uptake by chard and lettuce of soil cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), leaf (Pb), and zinc (Zn) was investigated. Ten different treatments (0, 150, 300, and 500 kg N ha^‐1) as mineral fertilizer, and 400, 800, and 1,200 kg N ha^‐1 of aerobically and anaerobically‐digested sewage sludges were applied annually to a sandy‐loam soil since 1984. Seven years after the start of the treatments, higher levels of heavy metals were detected in the soil, depending on the type of metal, depth of sampling, type of sludge used, and, especially, rate of application. Following a sequential extraction procedure incorporating 0.1M CaCl₂, 0.5M NaOH, and 0.05M Na₂EDTA, most of the heavy metals in soil were detected in the Na₂EDTA solution and the residual fractions. Large amounts of Cd appeared to be extracted by CaCl₂, whereas substantial amounts of Cu and Ni were isolated by NaOH. The effect of treatments on the percentages of the metals found in each fraction depended on the type of metal, sampling depth, sludge used, and application rate. No significant increases were found in the heavy metal contents of chard and lettuce leaves, but some of the treatments resulted in a significant decrease of Cd and Cr levels in lettuce leaves.     

Iron nutrition of sunflower(Helianthus annuus L.) as affected by various levels of p and ZN

The effects of various P and Zn levels on iron nutrition of sunflower (Helianthus annuus L.c.v. Record) were studied in two separate experiments in nutrient solution under greenhouse conditions.

In the first experiment, sunflower was grown in nutrient solutions containing four levels of P(1.5, 2.5, 3.5 and 4.5 mM/l) and three levels of Fe(0.25, 0.75, and 1.5 ppm) as FeCl₃ or FeEDDHA. In the second experiment (following the first experiment), the treatments were three P levels (0.75, 1.50 and 3.00 mM/l), three Fe levels (0.25, 0.75 and 1.5 ppm) as FeEDDHA and three Zn levels (0.1, 0.2 and 0.4 ppm).

The plants receiving Fe‐chelate, except for 0.25 ppm Fe, showed no symptoms of iron chlorosis. With inorganic Fe treatments, iron chlorosis appeared after 7–10 days depending on P level, but except for 0.25 ppm Fe which remained chlorotic, plants recovered completely within 3–4 days thereafter due to pH regulating mechanism of sunflower under iron stress condition. With both sources of Fe, chlorosis was associated with high P:Fe ratio.

Increased P and Fe levels in nutrient solution resulted in general increases in the dry weights of roots and shoots. The Fe concentration of shoots, except in few instances, was not affected by P levels, indicating that the sunflower cultivar used in this experiment could utilize inorganic Fe as well as Fe‐chelate under our experimental conditions.

Increasing P levels caused significant increases in Mn content of the shoots as 0.25 and 0.75 ppm inorganic Fe³⁺. Increased Fe levels increased shoot Mn content with inorganic Fe and decreased it with Fe‐chelate. The effects of P, Fe and Zn on sunflower indicated an antagonistic effect of Zn on 1.5 ppm Fe for all P levels. Increased Zn levels in nutrient solution generally increased Zn content of the shoots without having any marked effect on their Mn content.     

Significance of organic nitrogen uptake from plant residues by soil microorganisms as affected by carbon and nitrogen availability

Soil microorganisms can use a wide range of nitrogen (N) compounds. When organic N sources are degraded, microorganisms can either take up simple organic molecules directly (direct route), or organic N may be mineralized first and taken up in the form of mineral N (mineralization-immobilization-turnover [MIT] route). To determine the importance of the direct route, a microcosm experiment was carried out. Two types of wheat residue were added to soil samples, including younger residue with a carbon (C) to N ratio of 12 and older residue with a C to N ratio of 29. Between days 1 and 4, the gross N mineralization rate reached 8.4 and 4.0 mg N kg⁻¹ dry soil day⁻¹ in the treatment with younger and older residue, respectively. During the same period, there was no difference in protease activity between the two residue amended treatments. The fact that protease activity was not related to gross N mineralization, even though the products of protease activity are the substrates for N mineralization, suggests that not all organic molecules released from residue or soil N passed through the soil mineral N pool. In fact, when leucine and glycine were added, only 10 and 53% of the amino acid-N, respectively, was mineralized. The fraction of N taken up via the direct route was estimated to be 55 and 62% for the young and older residue, respectively. After 28 days of incubation, the proportion of amino acid-N mineralized had increased especially in the soil amended with older residue, suggesting that the MIT route became increasingly important. This result is supported by an increase in the activities of enzymes responsible for the intracellular assimilation of ammonium (NH₄⁺). Our results suggest that in contrast to what is proposed by many models of soil N cycling, both the direct and MIT routes were operative, with the direct route being the preferred route of residue N uptake. The direct route became less important over time and was more important in soil amended with older residue, suggesting that the direct route is favored by lower mineral N availabilities. An important implication of these findings is that when the direct route is dominant, gross N mineralization underestimates the amount of N made available from the residue.     

Cotton growth and boron distribution in the plant as affected by a temporary deficiency of boron

The knowledge of nutrient mobility is an important tool to define the best fertilizer management and diagnosis techniques. Patterns of boron (B) mobility in plants have been reviewed, but there is very little information on B distribution and mobility in cotton. An experiment was conducted to study plant growth and B distribution in cotton when the nutrient was applied in the nutrient solution or to the leaves, and when a temporary deficiency was imposed. Cotton (Gossypium hirsutum, Latifolia, cv. IAC 22) was grown in nutrient solutions where B was omitted or not for 15 days. Boron was applied to young or mature cotton leaves in some of the minus B treatments. Root growth decreased when the plants were transferred to B solutions, but there was a full recovery when B was replaced in the nutrient medium. Boron deficiency, even when temporary, reduced cotton shoot dry matter yields, plant height and flower and fruit set, and these could not be prevented by foliar application of B. Because of decreased dry matter production, leaves of deficient cotton plants actually showed higher B concentrations than non deficient leaves. This would be misleading when a mature leaf is sampled for diagnosis. If there is any B mobility in cotton phloem, it is very low.     

植物促生菌接种对中国芥蓝根际固有微生物群落结构的影响

Plant growth-promoting rhizobacteria (PGPR) have been widely recognized as an important agent,especially as a biofertilizer,in agricultural systems.The objectives of this study were to select efective PGPR for Chinese kale (Brassica oleracea var.alboglabra) cultivation and to investigate the efect of their inoculation on indigenous microbial community structure.The Bacillus sp.SUT1 and Pseudomonas sp.SUT19 were selected for determining the efficiency in promoting Chinese kale growth in both pot and field experiments.In the field experiment,PGPR amended with compost gave the highest yields among all treatments.The Chinese kale growth promotion may be directly afected by PGPR inoculation.The changes of microbial community structure in the rhizosphere of Chinese kale following PGPR inoculation were examined by denaturing gradient gel electrophoresis (DGGE) and principal coordinate analysis.The DGGE fingerprints of 16S rDNA amplified from total community DNA in the rhizosphere confirmed that our isolates were established in the rhizosphere throughout this study.The microbial community structures were slightly diferent among all the treatments,and the major changes depended on stages of plant growth.DNA sequencing of excised DGGE bands showed that the dominant species in microbial community structure in the rhizosphere were not mainly interfered by PGPR,but strongly influenced by plant development.The microbial diversity as revealed by diversity indices was not diferent between the PGPR-inoculated and uninoculated treatments.In addition,the rhizosphere soil had more influence on eubacterial diversity,whereas it did not afect archaebacterial and fungal diversities.     

Mineralization of plant residues and native soil carbon as affected by soil fertility and residue type

Journal of Soils and Sediments - Crop residue return is an effective and low-cost agricultural approach for soil organic carbon (SOC) sequestration. Yet, it is largely unknown to what extent the...     

Foliar sensitivity of pinto bean and soybean to ozone as affected by temperature,potassium nutrition and ozone dose

Pinto bean (Phaseolus vulgaris L.) and soybean [Glycine max (L.) Merv.] were exposed to O₃ to determine the interactions of growth temperature, exposure temperature, K nutrition and doses of O₃ on their foliar sensitivity. Pinto bean developed more foliar injury than soybean. Pinto bean were most sensitive when grown and exposed at 28°C. Growth and exposure temperature interacted in the development of foliar injury on pinto bean, but only growth temperature influenced the amount of foliar injury on soybean. Both species developed more foliar injury when grown with low K nutrition. There was no relationship between foliar injury and reducing sugars or sucrose content of the leaves.     

Soil movement by tillage as affected by slope

Exposure of subsoil material on ridge tops and adjacent sideslopes indicates soil movement away from these positions, i.e. soil erosion. A study was conducted on the University of Minnesota Southwestern Experiments Station to determine if soil movement by tillage could be a contributing factors to the apparent soil erosion present on many ridge tops. Numbered soil movement detection units (11-mm steel hexagonal nuts) were buried 10-cm deep in a grid network in 16 individual plots, on a sideslope with slopes ranging from 1 to 8%. Plots were moldboard plowed and disked in June, and again in August. The direction of tillage was either across the sideslope or up- and downslope. The soil movement detection units were then located with a metal detector, excavated and identified, and distance moved was measured in relation to movement perpendicular and parallel to the direction of tillage. Soil movement was directly related to slope. Movement perpendicular off the moldboard on the direction of tillage was greater than movement perpendicular off the moldboard. Calculations on the angle of movement in relation to tillage direction showed movement toward the downslope position. Results from this study suggest that soil movement by tillage can contribute to soil movement off ridge tops and adjacent sideslopes.