Excessive Nitrogen Fertilization Research Articles

Effect of Nitrogen Fertilization and Seed Contamination on Epiphytic Populations of Xanthomonas axonopodis pv. allii and Development of Xanthomonas Leaf Blight of Onion

Xanthomonas leaf blight of onion, caused by Xanthomonas axonopodis pv. allii, is a yield-limiting disease in Colorado, for which few effective management strategies are available. The effects of rates of nitrogen fertilization and levels of seed contamination by X. axonopodis pv. allii on epiphytic populations of the pathogen and subsequent disease development were determined in field studies over two years. Epiphytic populations of a rifampicin-resistant mutant were quantified from bulked, asymptomatic leaf tissue using a leaf wash assay. There was no significant relationship between nitrogen fertilization treatment and epiphytic population development, but excessive nitrogen (> 200 kg/ha) fertilization increased disease severity 27 to 50% compared with non-fertilized and low (112 kg/ha) nitrogen fertilizer treatments in 2004. Seed inoculated with various levels of X. axonopodis pv. allii did not result in persistent epiphytic populations of the bacterium or development of symptoms, even at 107 CFU/g of seed. The results of these studies suggest moderate rates of nitrogen fertilization may reduce severity of Xanthomonas leaf blight compared to higher rates, and that seed contamination by X. axonopodis pv. allii may be of limited importance for disease development under the semi-arid conditions of furrow-irrigated onion production in Colorado. Accepted for publication 13 March 2005. Published 31 March 2005.

Optimal Rates of Nitrogen Fertilization for a Winter Wheat-Corn Cropping System in Northern China

The sequential growth of winter wheat and corn within one year is the main cropping rotation system in northern China, excess nitrogen (N) fertilizer application to this system is a common problem. Four field experiments with four or five N rates were conducted in Beijing City and Henan province to study the optimal N rate for this system. The results of this study clearly indicate that the high rates of fertilization recommended by the quadratic model were less profitable than the lower rates recommended by the LRP and QRP models. The amounts of N in above-ground plant tissue tended to increase with increase in rate of N application but the percentage recovery of N in each increment decreased with each additional increment of fertilizer applied, and higher percentage recoveries were observed in wheat than in corn. Soil nitrate concentrations increased with increasing rates of N application. Average of 30% of the soil mineral N deficit can be accounted for uptake of N by wheat, but linear regression analysis showed no significant relationship between soil mineral N deficit and uptake N by corn. The relationships between soil mineral N deficit and mineral N in the soil before planting indicated that soil mineral N deficits were directly proportional to the amounts of mineral N initially in the soil. Good relationships were observed between relative yields and amounts of mineral N in the soil before planting, and the r 2 values for the relationships with nitrate to 40 cm were similar to those observed with nitrate to 100 cm. The need to sample no deeper than 40 cm increases the practicality of soil testing and adjusting rates of N fertilization.

SPATIAL VARIABILITY OF NITRATE IN CABBAGE AND NITRATE-N IN SOIL

Long-term use of excessive nitrogen fertilizer contributes to the accumulation of nitrate-N in soil and, in turn, can lead to excessive accumulation of nitrate in vegetable crops. Better understanding of the spatial variability of soil nitrate-N and vegetable nitrate can provide a basis for site-specific soil nutrient management and for rational nitrogen fertilization rates combined with balanced fertilization for high quality, high yield vegetable production. This study was conducted to determine spatial variability characteristics of soil nitrate-N (NO 3 - -N) and nitrate (NO 3 - ) in cabbage and their interrelationship in a 55-ha vegetable production area using traditional statistics and geostatistics. The study area comprised 182 farm plots belonging to six production groups (recorded as 1st, 2nd, 3rd, 4th, 7th, and 8th groups). A total of 217 soil samples 0-20 cm in depth were collected on a 50 × 50-m grid in the study area before cabbage seeding. Prior to the cabbage harvest, 217 samples of edible cabbage parts were collected at sites corresponding to the soil sampling locations. The history of vegetable production at all of the soil sampling sites-including varieties, rotations, and fertilizer use-was surveyed, and soil nitrate-N and cabbage nitrate were measured. The spatial variability structure of nitrate content in cabbage and nitrate-N content in soil increased at first and then decreased with increasing separation distance. The spatial correlation ranges for cabbage nitrate contents and soil nitrate-N contents were 305.0 and 165.0 m, respectively, indicating the existence of significant spatial continuity in nitrate in cabbage and nitrate-N in soil. Notable spatial distribution comparability was observed in the contents of nitrate in cabbage and nitrate-N in soil. The contents of nitrate in edible cabbage parts and nitrate-N in soil were higher in most areas of Group 2 and Group 7 than in Group 1, Group 3, and Group 4; the contents were relatively lower in most areas of Group 8. Spatial variability of nitrate in cabbage was correlated positively with nitrate-N in soil (R 2 = 0.413**, n = 217), whereas soil nitrogen-N contents were closely correlated with vegetable production history and nitrogen fertilizer application rates.

Nitrogen fertilization, soil nitrate accumulation, and policy recommendations in several agricultural regions of China.

Excessive nitrogen (N) fertilization and decreasing N recovery rates by crops have caused dramatic increases in non-point source pollution from agriculture in China. The rate of N fertilization across the country varies widely among regions and crops, depending on the stage of economic development. For example, N application rates in the eastern regions and on cash crops are far higher than in western regions of the country and on cereal crops. Moreover, N application rates in wealthier regions are higher than recommended by the Chinese Academy of Sciences. To successfully achieve environmental protection as well as high crop yields, China must formulate relevant agricultural policies to encourage farmers in economically developed areas to reduce their N fertilization rate while also issuing conventional fertilization recommendations for small-scale farming systems and the expanding cultivation of cash crops.

Cultural Practices that Impact Stone Fruit Quality

Quality of stone fruit is defined by fruit size, color, firmness, flavor, shape, general appearance, adhesion and size of the stone and fruit surface characteristics (e.g. fuzz, abrasions, pest damage). Cultural practices, such as pruning, nutrition, irrigation, growth regulator usage and pesticide applications can influence these quality characteristics to a greater or lesser extent. Adequate potassium nutrition can improve soluble solids and fruit size in plums. Excess nitrogen fertilization can soften peaches. Well-timed calcium sprays are thought to improve the firmness of sweet cherries, as are applications of gibberellin. Ethylene synthesis inhibitor usage can alter the timing of ripening, reduce early fruit drop and improve storage. Irrigation scheduling is a tool that can be used to regulate final fruit size and firmness, as well as time of maturation. Selective pruning is used to structure a tree's architecture for improved light penetration to improve fruit size and color. These and other production practices will be discussed in relation to how they affect fruit quality in stone fruit.

Cucurbits under protected cultivation

Cucurbits under protected cultivation

The effect of irrigation and nitrogen on powdery scab and yield of potatoes

Powdery scab, caused by the fungusSpongospora subterranea, has developed in the Cappodocia region of Turkey because of changes in agronomic practices, such as excessive irrigation and nitrogen fertilizer use and growth of highly susceptible cultivars. The most suitable irrigation and nitrogen application levels were established to maintain powdery scab at minimum levels without affecting potato yield. Three irrigation levels were used in 1998 (673, 897, 1121 mm) and five in 1999 (329, 494, 658, 823, 987 mm). Nitrogen levels were applied 150, 300, 450, 600 kg N ha−1. In 1998, least powdery scab occurred with 673 mm irrigation, which yielded 41 t ha−1 potatoes. The lowest disease severity occurred in 1999 with 494 mm irrigation and 150 kg N ha−1. At these levels, tuber yield was 34 t ha−1 which was not significantly different from the highest yield measured. In 1999 and at two of the three irrigation levels inl998, nitrogen increased disease severity.

Nitrate leaching in temperate agroecosystems: sources, factors and mitigating strategies

Nitrate (NO3 −) leaching from agriculturalproduction systems is blamed for the rising concentrations ofNO3 − in ground- and surface-waters around the world.This paper reviews the evidence of NO3 − leachinglosses from various land use systems, including cut grassland, grazed pastures,arable cropping, mixed cropping with pasture leys, organic farming,horticultural systems, and forest ecosystems. Soil, climatic and managementfactors which affect NO3 − leaching are discussed.Nitrate leaching occurs when there is an accumulation ofNO3 − in the soil profile that coincides with or isfollowed by a period of high drainage. Therefore, excessive nitrogen (N)fertilizer or waste effluent application rates or N applications at the wrongtime (e.g. late autumn) of the year, ploughing pasture leys early in the autumn,or long periods of fallow ground, can all potentially lead to highNO3 − leaching losses. N returns in animal urine havea major impact on NO3 − leaching in grazed pastures.Of the land use systems considered in this paper, the potential for causingNO3 − leaching typically follow the order: forest< cut grassland < grazed pastures, arable cropping < ploughing ofpasture < market gardens. A range ofmanagement options to mitigate NO3 − leaching isdescribed, including reducing N application rates, synchronizing N supply toplant demand, use of cover crops, better timing of ploughing pasture leys,improved stock management, precision farming, and regulatory measures. This isfollowed by a discussion of future research needs to improve our ability topredict and mitigate NO3 − leaching.

Need for determining ecofriendly optimum fertilizer nitrogen level for better environment and for alleviating hunger and malnutrition

Asia accounts for about two-thirds of hungry and malnourished people in the world and within Asia, South Asia, which includes India, Pakistan and Bangladesh accounts for about 34.3%, which in absolute numbers are 276.4 million people. Cereals are the staple food in Asia and alleviation of hunger aims at increasing the availability of cereals (rice, wheat, maize etc.) in these countries. It is estimated that without fertilizer nitrogen about half of the world population would have remained hungry and malnourished. However, excess fertilizer nitrogen is detrimen- tal to the environment. Ammonia volatilized from surface applied fertilizer nitrogen reduces air quality, while ni- trous oxide is a powerful greenhouse gas contributing to global warming and is also responsible for depletion of atmospheric ozone. Excessive nitrogen fertilizer is reported to increase nitrate concentration in drinking water leading to blue baby syndrome or methaemoglobinemia, while eutrophication of surface water is responsible to mortality of fish and other sea creatures. Therefore, efforts are underway to increase the efficiency of fertilizer ni- trogen by using 4Rs, namely, right source applied at the right rate, time and depth. A number of studies have indi- cated that it is possible to obtain the desired production of cereals with much lesser nitrogen rates and it is sug- gested to shift from economic optimum rate (Econ ) to ecological optimum rate (Ecol ) rate of nitrogen applica- opt opt tion to cereals in making out fertilizer recommendations. This exercise has not yet been done by the agronomists in India and is strongly recommended.

Effect of Nitrogen Fertilization on Growth, Canopy Density, and Yield ofVitis viniferaL. cv. Cabernet Sauvignon

The effect of nitrogen supply on the vegetative and reproductive capacity of vines of low nitrogen status was investigated in a field trial conducted in Western Australia. Five rates of nitrogen fertilizer (0, 50, 100, 200, and 400 g N/vine) were applied to irrigated, 12-year-old Cabernet Sauvignon vines over three seasons. Two-thirds of the nitrogen was applied late budbreak and the rest at two weeks after flowering. Moderate rates of nitrogen fertilization stimulated vine growth and vigor (shoot extension rate) resulting in an increase in canopy density. Prior to flowering, maximum vine vigor was observed upon addition of 100 g N/vine. This effect was no longer evident after flowering. Those vines supplemented with 100 g of nitrogen also achieved maximum petiole nitrate concentrations at flowering, growth (shoot length, pruning weight, and leaf area), and canopy density (leaf layer number). Vines receiving 400 g N/vine had shorter shoots and less pruning weight than vines receiving 100 g N/vine, as vigor did not respond to nitrogen fertilizer prior to flowering. However, the petiole nitrate concentration, total leaf area, and canopy density of vines supplied with 200 to 400 g N/vine were no different to those vines supplemented with 100 g N/vine. Nitrogen had no effect on the total vine yield in the first and last season. However, the highest yield came from vines receiving 100 g N/vine in the second season. Additional applications of 200 g and 400 g N/vine increased the yield no further. Higher berry numbers per bunch were associated with the increase in total vine yield. It appeared that moderate rates of nitrogen fertilization can have a beneficial effect on vine productivity in situations where vine nitrogen status is low. In contrast, excessive nitrogen fertilization was an unprofitable exercise as it provided no further benefits in terms of vine productivity.

Excess nitrogen raises nectarine susceptibility to disease and insects

This multidisciplinary study examined the effects of nitrogen fertilization on nectarine yield, fruit quality, brown rot and moth pests. Results indicate that excess nitrogen fertilization did not increase fruit yield or improve fruit quality; however, fruit on overfertilized trees were more susceptible to attack from brown rot, peach twig borer and oriental fruit moth.

Excess nitrogen fertilization and the structure of Scots‐pine needles

SummaryThe effects of excess nitrogen fertilization on the structure of Scots‐pine needles (Pinus sylvestris) were examined in Finnish Lapland. The trees were fertilized with calcium ammonium‐nitrate, and the levels of nitrogen applied were 0, 75, 150, 250, 500 and 1000 kg N/ha, respectively. The thickness and width of the needle and thicknesses of the tissues were measured, and the conditions of various celltypes were classified at the light‐microscopy level. In addition, the areas of the cell organelles were measured and the conditions of the chlomplasts and other cell compartments observed at the ultrastructural level. Larger needles and a thicker adaxial mesophyll were observed following excess N application (250–1000 kg N/ha). The natural xeromorphic structure of the conifer needles became more mesomorphic, possibly influencing the protection afforded against environmental stresses. A high level of nitrogen fertilization caused changes in the central cylinder, especially in the vascular bundle and the sclerenchyma. The needle nitrogen concentration was high in the highly fertilized trees and the boron concentration was simultaneously extremely low. As a consequence of the changes in the central cylinder, photoassimilate transport from the mesophyll to the phloem may be disturbed at high fertilization levels. The changes at the ultrastructural level, i.e. injuries to the chloroplast thylakoids and the plasma membrane, and the formation of lipid accumulations, were indicators of the adverse effects of excess nitrogen. With an increasing atmospheric‐nitrogen load, lower nitrogen fertilization levels in pine forests naturally adapted to low soil N should be considered in forest management.

The effect of farming practices on reducing excess nitrogen fertilizer use

A nitrogen balance model is used to investigate the adoption of a crop rotation and the limitation on the application of nitrogen fertilizer to reduce excess nitrogen. For a farmer initially planting corn continuously, the adoption of a soybeans-corn rotation will have a smaller compliance cost but it will not eliminate the excess application of nitrogen fertilizer under a relatively low nitrogen fertilizer to corn price ratio. An explicit limitation on nitrogen fertilizer use would be needed to achieve this objective. Limiting nitrogen fertilizer use on cropland susceptible to a high potential for leaching will have a smaller compliance cost than on cropland with a moderate potential for leaching.

The effect of crop rotation on reducing excess nitrogen fertilizer use

Among the various policy options available to reduce the excess application of nitrogen, including restricting the nitrogen fertilizer application rate and taxing nitrogen fertilizer, adoption of a soy-bean–corn rotation, while coincidentally limiting the nitrogen fertilizer application rate, will have the lowest compliance cost for a farmer. This rotation also will be the most efficient option, by maintaining a profitable level of crop production irrespective of the ratio of the nitrogen fertilizer price and the corn price. Using rotation on cropland with a high potential for leaching will have a smaller compliance cost relative to that found when the cropland has moderate leaching potential.

An Assessment of Planting Flexibility Policy Options

This study estimates the marginal value of a base acre under alternative policy options designed to encourage planting flexibility. Also computed are the rate of nitrogen fertilizer use, the corn yield and the excess nitrogen fertilizer application rate. Moving toward the elimination of base acreage is the most effective way to reduce the value of a base acre thereby encouraging greater planting flexibility. An increase in the price of soybeans and a decrease in the price of corn would also serve to encourage switching from continuously planting corn to a corn-soybeans rotation.

A Comparison of Farmers' Compliance Costs to Reduce Excess Nitrogen Fertilizer Use under Alternative Policy Options

Farmers' compliance associated with using different crop rotation patterns under alternative farm policy options are estimated. The policy options considered include the Current Farm Program, a No Farm Program Option, a Nitrogen Fertilizer Tax Option, a Corn Sales Tax Option, and a Limiting Nitrogen Fertilizer Use Option. To achieve an objective of zero excess nitrogen fertilizer available for potential leaching into ground-water, crop rotation patterns associated with the Limiting Nitrogen Fertilizer Use Option have the lowest cost to the farmer. If some excess nitrogen is allowed, crop rotation compliance under the Farm Program has the lowest cost.

The effect of farming practices on reducing excess nitrogen fertilizer use

This paper studies the effects of crop rotation and a limitation on the application of nitrogen fertilizer on the reduction of excess nitrogen available for potential leaching into the ground water. For a farmer initially planting corn continuously, the adoption of a soybean-corn rotation will have a smaller compliance cost, but it will not eliminate the excess application of nitrogen fertilizer under a relatively low nitrogen fertilizer to corn price ratio. An explicit limitation on nitrogen fertilizer use would be needed to achieve this objective. Limiting nitrogen fertilizer use on cropland susceptible to a high potential for leaching will have a smaller compliance cost than on cropland with a moderate potential for leaching.

Nitrate pollution of groundwater in the alsatian plain (France)—A multidisciplinary study of an agricultural area: The Central Ried of the ill river

The area studied is part of the “Ried Central” of the Ill river (Middle Alsatian plain in northeastern France). This area is located mainly in the present floodplain of the Ill. The closeness of the water table to the surface results in quasi general soil hydromorphism. The economic constraints of the last two decades led to deep changes in agricultural activities in the study area. These have essentially involved a marked extension of intensive cultivation of grain corn at the expense of grasslands. The study of the influence of this change on the parallel increase in the concentration of nitrate in groundwater is only feasible when a multidisciplinary approach is adopted. The analyses carried out in the field and in the laboratory show that nitrate reduction occurs in gleyed or peaty horizons of hydromorphic soils. The aptitude and efficiency of the permanent ambient vegetation (alluvial forests and grasslands) in retaining nitrate must be emphasized. The amount of nitrate eliminated from the aquifer by rivers fed by this aquifer is considerable. This evacuation of nitrate into the Ill is a fine example of waste and illustrates the absurdity of the economic situation responsible for excessive nitrogen fertilization of farmlands. In determining hazard zones, this study also proposes practical solutions to the problem of nitrate pollution: diminution of land area under cultivation, reintroduction of grasslands, and a more judicious use of nitrogen manure.

An Assessment of Planting Flexibility Options to Reduce the Excessive Application of Nitrogen Fertilizer in the United States of America

The analysis in this paper is directed at estimating the marginal value of a base acre, the nitrogen rate of fertilizer use, the corn yield, and the excess nitrogen fertilizer application rate under alternative policy options designed to encourage planting flexibility in response to changing relative agricultural commodity prices. Encouragement of planting flexibility via an option of detaching deficiency payments from the base acreage is an effective way to reduce the excessive application rate and use of nitrogen fertilizer. Encouragement of planting flexibility via an option of reducing the base acreage is effective only if the availability of cropland is a limiting factor. However, movement toward the complete elimination of the notion of base acreage (that is, movement toward a completely free market unencumbered by government programs) would be the most effective option to reduce the value of a base acre thereby encouraging greater planting flexibility. An increase in the price of soybeans and a decrease in the price of corn would also serve to encourage switching from continuous planting of corn to a corn — soybeans rotation. However, as more soybeans and less corn are produced, the price of soybeans would fall while the price of corn would rise. As a consequence, the effectiveness of the policy options considered here in promoting planting flexibility would be reduced.

An analysis of the marginal value of cropland and nitrogen fertilizer use under alternative farm programs

The analysis in this paper is directed at estimating the impact on the marginal value of a crop base acre and on nitrogen fertilizer use of alternative farm programs designed to encourage planting flexibility in response to changing relative agricultural commodity prices. Four policy alternatives are considered: the current farm program, the Normal Crop Acreage option, the triple-base option, and the Lugar-Leahy (USDA) option. Encouraging planting flexibility via the Lugar-Leahy (USDA) option can be an affective way to reduce the excessive application of nitrogen fertilizer. Additionally, an effective farm policy designed to encourage growing crops beside those used to calculate the base acreage should detach any program deficiency payments from the number of program base acres. For example, the triple-base option would lower the marginal value of a base acre and therefore would increase the likelihood of a farmer adopting some sort of crop rotation scheme (as opposed to continuously planting the same program crop). The accompanying reduction in the excessive nitrogen fertilizer application rate, however, might not be substanial because the triple-base option links deficiency payments to the number of base acres. The Lugar-Leahy (USDA) option, on the other hand, is an effective way to reduce the excessive nitrogen fertilizer application rate while at the same time inducing farmers to consider the production of alternative crops.