Urea-treated Plants Research Articles

Peat-Based Organo-Mineral Fertilizer Improves Nitrogen Use Efficiency, Soil Quality, and Yield of Baby Corn (Zea mays L.)

The application of organo-mineral fertilizers (OMFs) is gaining popularity day by day because of their potential effect on crop productivity and soil fertility enhancement. Therefore, this research was conducted to observe the effect of a peat soil–urea (PSU) fertilizer on baby corn yield, quality, nitrogen (N) use efficiency, and soil quality compared with commercial urea. A completely randomized design (CRD) with four replicates was used to set up the experiment. In this trial, N was applied from three sources, viz., urea, PSU-L (low N = 15%), and PSU-H (high N = 25%) at a rate of 50, 75, and 100% of the recommended N application dose. The growth, yield, quality, and N use efficiency of baby corn were significantly impacted by the application of PSU fertilizer to the soil. Substantially higher leaf chlorophyll, cob vitamin C, and protein content were found in PSU-treated plants compared with commercial urea. The application of PSU produced about 21% higher cob and a 14% fodder yield over commercial urea. On average, the N uptake by baby corn was 22% higher in PSU-treated plants than urea-treated plants, resulting in 24 and 33% higher N use efficiency and fertilizer N use efficiency, respectively, in PSU than commercial urea. Therefore, the N application rate could be reduced by around 30% using PSU as an alternate N source compared with using commercial urea. In addition, the application of PSU to soil substantially increased the soil organic carbon (SOC) content, whereas SOC decreased in urea-treated soil.

N-Fertilizer (Urea) Enhances the Phytoextraction of Cadmium through Solanum nigrum L.

Heavy metal contamination is currently a major environmental concern, as most agricultural land is being polluted from municipal discharge. Among various other pollutants, cadmium (Cd), one of the most harmful heavy metals, enters into the food chain through the irrigation of crops with an industrial effluent. In the present study, a pot experiment was designed to assess the effect of different nitrogen (N)-fertilizer forms in the phytoremediation of Cd through Solanum nigrum L. Two types of N fertilizers (NH4NO3 and urea) were applied to the soil in different ratios (0:0, 100:0, 0:100, and 50:50 of NH4NO3 and urea, individually) along with different Cd levels (0, 25, and 50 mg kg−1). The plants were harvested 70 days after sowing the seeds in pots. Cadmium contamination significantly inhibited the growth of leaves and roots of S. nigrum plants. Cadmium contamination also induced oxidative stress; however, the application of N-fertilizers increased the plant biomass by inhibiting oxidative stress and enhancing antioxidants’ enzymatic activities. The greatest plant growth was observed in the urea-treated plants compared with the NH4NO3-treated plants. In addition, urea-fed plants also accumulated higher Cd concentrations than NH4NO3-fed plants. It is concluded that urea is helpful for better growth of S. nigrum under Cd stress. Thus, an optimum concentration of N-fertilizers might be effective in the phytoremediation of heavy metals through S. nigrum.

Application of Landfill Leachate Improves Wheat Nutrition and Yield but Has Minor Effects on Soil Properties.

Landfill leachates, which are potential pollutants, may also carry significant amounts of nutrients that can be recycled by plants. We assessed the nutritional status and yield of wheat ( L.) and properties of a Rhodic Kandiudult soil (depths of 0-10, 10-20, 20-40, and 40-60 cm) after 11 applications of landfill leachate over 4 yr. In the last application, wheat received 0, 32.7, 65.4, 98.1, or 130.8 m ha (875 mg L of nitrogen, N) of leachate and a positive control (90 kg ha of N as urea) 15 d after sowing. Urea increased nitrate (>160 mg kg) in the topsoil (down to 40 cm), whereas landfill leachate increased nitrate (>60 mg kg) only at 40 to 60 cm with the highest dose, suggesting leaching. Urea-treated soil had less negative ΔpH, which might have led to greater retention of nitrate in the topsoil. Sodium (0.02-0.26 cmol Na kg), potassium (0.18-0.82 cmol K kg), and electrical conductivity (0.05-0.14 dS m) all increased with leachate dosage. Treatments did not affect resistance to penetration and clay dispersion. Basal respiration increased with leachate dosage, whereas dehydrogenase activity decreased, suggesting effects on soil microbial metabolism. Microbial biomass and soil enzyme activities were not affected by addition of leachate. Nitrogen nutrition (15.1-22.7 g N kg in flag leaves) and grain yield (1381-2378 kg grain ha) increased with leachate dosage so that the highest dose gave results similar to those for urea-treated plants (2563 kg grain ha). Landfill leachate showed strong potential as source of N for wheat but caused none, or transient, effects on soil properties. However, nitrate from leachate was more leachable than nitrate from urea.

Maize Response to a Synthetic Organic Nitrogen Fertilizer, Poultry Manure and Time of Application in the Guinea Savannah of Nigeria

Two field experiments were conducted at the Teaching and Research Farm of the University of Ilorin, located in the Guinea savannah agro-ecological zone of Nigeria, to study the effects of a synthetic organic nitrogen fertilizer (Urea) and poultry manure (Pm-a natural organic nitrogen source) and their time of application on growth and yield of maize (Zea mays L.). The response of maize to the two sources of nitrogen varied significantly with time of application. Urea applied at 4 and 6 weeks after planting (wap) gave the best crop performance while poultry manure applied between planting and 4 wap recorded better crop performance than the other times of application. Maize growth and grain yield were consistently better in poultry manure and urea-treated plants than in the no-fertilizer control treatment at p

Effects of Controlled Release Urea on the Yield and Nitrogen Nutrition of Flooded Rice

Nitrogen (N) loss is one of the key problems faced by rice farmers, and Nitrogen-use efficiency in rice is often poor as a result of high N loss through volatilization, leaching, and denitrification. One of the ways to improve N efficiency is by using controlled-release urea (CRU). The CRU generally outperformed granular urea fertilizer in reducing N losses, stimulating plant growth, and increasing N concentrations. A field experiment with the flooded rice variety MR220 was conducted to compare the effect of six different types of CRU fertilizers on yield and N nutrition of a flooded rice cultivar. Bakau series soil (Typic Tropaquept) was used in this study. Rice plants were grown in a cylindrical culvert measuring 90 cm in diameter by 60 cm in height, and all culverts were filled with soil (approx. 210 kg). The soil was flooded and preincubated for 3 weeks to stabilize physiochemical properties before sowing. The experiment was carried out over two planting seasons on the same plot using a completely randomized design (CRD) and was replicated three times. The CRUs evaluated were CDU Uber-10, Meister-20, Meister-27, humate-coated urea, Duration type V, and sulfur-coated urea (gold–N). Fertilizer was applied once throughout the study. For both seasons, CRU-treated plants had significantly greater rice yields [6 t ha−1 (first planting harvest) and 6.2 t ha−1 (second planting harvest)] than urea-treated plants [3.7 t ha−1 (first planting harvest) and 2.2 t ha−1 (second planting harvest)], respectively. The N accumulations in rice straw and rice grains of the CRU-treated plot were significantly greater than in the control. It can be inferred that CRU performs significantly better than granular urea. This finding is important, considering the usually high N losses in rice-growing areas.

Plant growth, metabolism and adaptation in relation to stress conditions: Further studies supporting nullification of harmful effects of salinity in lettuce plants by urea treatment

Foliar application of urea to lettuce plants induced pronounced changes in the total amount and in the relative composition of the nitrogen pool. As compared with untreated lettuce plants, urease (UR), nitrate reductase (NR), asparaginase (AS) and glutamine synthetase (GS) activities were, in general, increased with an increase in the concentration of urea. On the other hand, salinization of lettuce plants with NaCl induced a significant decrease in the activities of UR, NR, AS and GS, at vegetative and adult growth stages. In general, treatment of lettuce plants with increasing concentrations of urea fertilizer in combination with each of the levels of salinity resulted in significant increases in all enzyme activities. Treatment with increasing concentrations of urea fertilizer induced significant decreases both in glycine and proline contents below control levels. On the other hand, salinization of lettuce plants with NaCl induced significant pronounced increases in the contents of the two amino acids. Further increments in glycine and proline contents were observed in differently salinized lettuce plants foliary sprayed with increasing concentrations of urea at vegetative and adult growth stages. Salinity solely enhanced the occurrence of novel proteins that were detected neither in the water control nor in the urea-treated plants. Protein banding patterns of lettuce plants treated with urea either alone or in combination with NaCl showed different <I>de novo </I>protein bands with different molecular weights, induced by urea and/or NaCl at vegetative and adult growth stages.

Chaotropic effects on 2,4,6-trinitrotoluene uptake by wheat (Triticum aestivum)

Previous research in our laboratory investigated the effectiveness of a common agrochemical, urea used as a chaotropic agent to facilitate 2,4,6-trinitrotoluene (TNT) removal by vetiver grass (Vetiveria zizanioides L.). Chaotropic agents disrupt water structure, increasing solubilization of hydrophobic compounds (TNT), and enhancing plant TNT uptake. Our findings showed that urea significantly enhanced TNT uptake kinetics by vetiver. We hypothesized that the beneficial effect of urea on the overall TNT uptake by vetiver grass was not plant-specific. We explored this hypothesis by testing the ability of wheat (Triticum aestivum L.) in removing TNT from aqueous media in the presence of urea. Results showed that untreated (no urea) wheat exhibited a slow, kinetically limited TNT uptake that was nearly half of the urea-treated wheat TNT capacity (250 mg kg−1). Chaotropic effects of urea were illustrated by the significant (P < 0.001) increase in the TNT second-order reaction rate constants over those of the untreated (no urea) controls. Plant TNT speciation showed that TNT and several of its metabolites were detected in both root and shoot compartments of the plant, allowing for 110 and 36% recovery for the untreated and 0.1% urea treated plants. The lower % recovery of the urea-treated plants was attributed to a number of unknown polar TNT metabolites.

EFFECT OF WATER MANAGEMENT AND POLYOLEFIN-COATED UREA ON GROWTH AND NITROGEN UPTAKE OF INDICA RICE

ABSTRACT Poor water management and high nitrogen (N) losses are the key problems faced by rice farmers under rainfed inland valley systems. There is a need to evaluate different N fertilizers so as to identify one that could withstand these problems. The performance of polyolefin-coated urea (POCU) was therefore compared with conventional urea in a pot experiment with indica rice (Oryza sativa L. cv. IR36), using two water management systems: 1) Submerged condition referred to as good water management (GWM), and 2) excessive irrigation (over 4000 mm in 120 days) referred to as poor water management (PWM). The study was carried out during 1997 and 1998 cropping seasons under glasshouse conditions. For PWM in 1997, the pots were subjected to leaching only whereas in 1998, they were subjected to both surface runoff and leaching. For both cropping seasons, POCU-treated plants under PWM had a significantly higher grain yield (377.5 and 343.0 g m−2) than urea-treated plants (316.5 and 260.5 g m−2). In addition, POCU-treated plants had a significantly higher number of grains per panicle than urea-treated plants. In 1998, both the partial factor productivity of applied N and the agronomic nitrogen-use efficiency of POCU-treated plants under GWM and PWM were significantly higher than those of urea-treated plants. It can be inferred that (using sandy soils and under PWM), POCU could perform significantly better than conventional urea. This finding is important, considering the usually high nitrogen losses in rice-growing inland valley swamps.

Foliar urea pretreatment tempers inefficient N recovery resulting from copper chelate (CuEDTA) defoliation of apple nursery plants

SummaryCopper chelate (CuEDTA) defoliation of deciduous fruit nursery plants, although effective in leaf removal, causes inefficient N recovery from leaves, which results in reduced reserve N levels in woody perennial tissues, compared with natural defoliation. To correct this problem, we sprayed spring bench-grafted Fuji/M.26 apple (Malus domestica Borkh.) nursery plants with 3% urea twice, at 5 d intervals, 13.d prior to 1% CuEDTA spray treatment on 31 October, 1997. The effects of urea and CuEDTA on defoliation, reserve N, and later regrowth were determined, as compared with those of hand- or natural-defoliation. CuEDTA resulted in >80% defoliation within 6 d of application. The abscission induced by the CuEDTA treatment, however, did cause significantly less N to be withdrawn from leaves compared with those plants undergoing natural defoliation. This inefficient N recovery was tempered by the foliar-urea pretreatment. The application of urea substantially increased the reserve-N level (total-N or soluble-protein concentrations) in all components of the tree without affecting the efficacy of CuEDTA on defoliation. The extent of regrowth in N-deficient medium was proportional to the reserve-N level. The urea-treated plants, whether hand- or CuEDTA-defoliated, showed better growth performance than the no-urea controls. Therefore, CuEDTA, in combination with pretreatments of foliar urea, proved effective for defoliating apple nursery plants, increasing reserve-N levels, and improving regrowth performance during tree establishment.

244 Effects of Fall Urea and Copper Chelate (CuEDTA) Application on Defoliation, Reserve Nitrogen, and Spring Regrowth of `Fuji' Apple Nursery Trees

Bench-grafted `Fuji'/M.26 trees were sprayed with 1% CuEDTA on 31 Oct., defoliated manually on 12 Nov., or allowed to defoliate naturally. Foliar urea at 3% was applied at 14 days and 9 days before CuEDTA treatment. Plants were harvested after natural leaf fall and stored at 2 °C. One set of the plants were destructively sampled for reserve N (expressed as total Kjeldahl N or soluble protein concentration) analysis, and the remaining plants were transplanted into a N-free medium in the spring without any N supply for 40 days after budbreak. CuEDTA resulted in &gt;80% defoliation within 5 days of application. Trees defoliated with CuEDTA had lower reserve N content than naturally defoliated controls, but had higher N than hand-defoliated controls. Foliar urea application before the CuEDTA treatment significantly increased reserve N level in all tree parts, without affecting the efficacy of CuEDTA on defoliation. The extent of spring regrowth was proportional to the reserve N level of the tree. Urea-treated plants, whether hand- or CuEDTA defoliated, had more growth in the spring than hand- or naturally defoliated controls. It is concluded that CuEDTA, as combined with foliar urea, can be used to effectively defoliate apple nursery trees, and increase reserve N level and improve regrowth performance during establishment.

Absorption and Assimilation of Foliarly Applied Urea in Tomato

In short-term experiments (10 days), urea applied foliarly as the sole N source promoted growth of `T-5' tomato (Lycopersicon esculentum Mill.) seedlings. The optimum urea concentration in the spray solution was 0.2% (w/w), and the best application frequency was once a day. Higher urea concentrations suppressed growth, producing severe leaf damage. The growth observed with foliar urea was less than that observed when inorganic N was supplied to the nutrient solution. Tomato seedlings absorbed 75% of the foliar applied urea within 12 hours and 99% within 24 hours after application. Urea concentrations in the plant tissues increased rapidly after foliar application. The maximum concentration was obtained in shoots at 12 hours and in roots at 24 hours after application. After that, concentration in the tissue declined to its original value within 48 hours. Tissue ammonium concentrations also increased after foliar application of urea. Shoot and root ammonium concentrations reached a maximum after 12 hours and stayed constant for the remainder of the 48-hour observation period. In the long-term experiment (5 weeks), the growth obtained with daily foliar applications of urea as the sole N source was only 10% of that when mineral N was available in the nutrient solution. Ammonium concentrations in the tissues of urea-treated plants were higher than those of plants treated with mineral N in the nutrient solution. Although urea concentrations were initially higher in plants treated with mineral N, after 2 weeks urea concentrations declined in these plants and increased in the shoots of plants receiving foliar applications of urea. These results indicate 1) that urea applied foliarly can supply at least part of the N required to sustain growth; 2) that urea is absorbed and assimilated fast enough to alleviate N deprivation; and 3) that failure to promote rapid growth with foliar urea is probably due to phytotoxicity and not to N deprivation.

Uptake and partitioning of selected mineral elements in sunflower (Helianthus annuus L.) during growth

The accumulation, distribution and redistribution of selected mineral elements in Helianthus annuus L. cv Hysun 21 are described. Plants were grown under glass to avoid damage by pests and leaching losses by rain. Uptake of P, K, S, Mg, Ca and Cl occurred well into seed filling. Patterns of distribution of the elements within the plant differed markedly. Seeds accumulated 79% of the mature plant's P, 18–31% of its Mg, K and S, but only 5–7% of its Ca and Cl. Roots had less than 11% and stems less than 20% of the amount of each element found in mature plants. Leaves had the highest proportion of the total plant P, S, K, Mg and Ca at three-row anthesis, but values for P, K and Cl decreased markedly during seed filling. Mature leaves had most of the plant's Ca, Mg and S, and the capitulum had most of the plant's K and Cl. Redistribution of P and K from senescing organs was considerable but low or negligible for other elements. Above-ground parts of the plant could have provided 31% and 13% of the P and S accumulated by seeds. K was redistributed from the stem and leaves but moved to the capitulum rather than to the seeds. Evidence is presented that the transport of nutrients, either in whole plants or plant parts, was not coupled directly to movement of assimilates. Only P showed a net transfer (85%) from cotyledons of parent seeds to seedlings. The kernel had most of a harvested seed's P, S, Mg and K; the pericarp had a high proportion of the seed's Cl, Na and Ca. There were differences in the mineral compositions of plants when either urea or nitrate was the N source. Nitrate-treated plants had significantly higher concentrations of cations but lower concentrations of chloride than urea-treated plants.

Studies on Aspergilli

The effect of foliar sprays of urea on the Aspergilli of the rhizosphere ofTriticum vulgare L was studied in detail. In all 16 species ofAspergillus were isolated from the rhizosphere region of wheat. The urea-treated plants (five sprayings) registered largest number ofAspergillus species. Out of 16 species the percentage occurrence of the following species,A. nidulans, A. rugulosus, A. sydowi A. fumigatus, A. niger andA. flavus, increased with the sprayings of urea. There was a general increase in the concentration of amino acids in urea-treated plants. But fourfold increase in the concentration was noted in the case of γ-aminobutyric acid and glutamine. In contrast to this the concentration of organic acids decreased as the sprayings increased.

The Influence of Foliar Applications of Urea on the Nodulation Pattern of Certain Leguminous Species

In greenhouse experiments with seven species of legumes, the spraying of urea on to the leaves was shown to affect nodulation adversely, without impairing the growth of the plants. In Phaseolus vulgaris , Vicia sativa , and Pisum sativum threetimes-weekly sprays of i per cent, aqueous urea either prevented or markedly reduced nodule development during the 8-week experimental period. In Medi cago sativa and Trifolium pratense the urea treatment resulted in a delay in nodulation so that numbers of nodules at the first sampling (4 weeks) were reduced, while numbers at later samplings were higher since nodulation had been delayed until the root system was larger and provided a greater number of potential nodule sites. In Trifolium hybridům and T. repens the urea-treated plants showed reduced nodulation throughout the 6-week experimental period. In these experiments the adverse effects on nodulation cannot be due to high concentration of combined nitrogen in the rooting medium, but it is suggested they derive from a high level of nitrogen within the plant.