Graduation date: 1991

One must consider the effects of both soil N and fertilizer N, if rates of N-fertilizer application are to be optimized and NO$ sb3 sp-$ leaching into groundwater be controlled. Objectives were (1) to determine soil $ rm NO sb3 sp-$-N and NH$ sb4 sp+$-N, soil total N, and N fertilizer levels and corn and wheat yields; and, (2) to determine soil sampling times and depths for N analyses that correlated with yields and fertilizer N response. Soil samples taken at seeding and postseeding were analyzed for NH$ sb4 sp+$-N and NO$ sb3 sp-$-N, and for total N in 29 wheat sites and 44 corn sites fertilized with four rates of N. N-Trak (quick test) and laboratory methods were employed to measure soil NO$ sb3 sp-$-N. A significant correlation was found between N-Trak and laboratory methods (R$ sp2$ = 0.61$ sp{**}$ for corn and 0.89$ sp{**}$ for wheat). Compared to the laboratory method, N-Trak overestimated soil NO$ sb3 sp-$-N. Soil NO$ sb3 sp-$-N levels increased upon drying. In some cases soils showed an increase in soil NO$ sb3 sp-$-N from seeding to postseeding. Wheat yields and wheat grain N uptake were better correlated with soil NO$ sb3 sp-$-N at seeding than at postseeding. For corn, yields and grain uptake showed a higher correlation with soil NO$ sb3 sp-$-N at postseeding. Corn regression models predicted 180 to 240 kg ha$ sp{-1}$ of N fertilizer to obtain optimum economic yields and 0 to 40 kg ha$ sp{-1}$ N for wheat. Soil total N was not correlated with corn yields as highly as soil NO$ sb3 sp-$-N. Soil NO$ sb3 sp-$-N can be used as an indicator of fertilizer N requirements for corn and wheat in Quebec.

Made available in DSpace on 2016-12-08T16:44:52Z (GMT). No. of bitstreams: 1 PGPV05MA001.pdf: 585348 bytes, checksum: d071c231c57e121ed066d664eba3e186 (MD5) Previous issue date: 2005-12-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The wheat cultivars differed substantially in terms of tiller emission, plant architecture and growing cycle duration. Such differences may interfere in the ideal period to side-dress N to optimize the crop agronomic performance. This experiment was carried out aiming to identify the effects of timing of N side-dress on the main stem and tiller dry mass accumulation, grain yield and yield components, and plant nitrogen accumulation and kernel protein content of three wheat cultivars. A field trial was conducted during the 2003 growing season, in the city of Lages, SC. Nitrogen was applied at four different times: 3,5, 5,5, 7,5 growth stages of the Haun s Scale and at booting. Three cultivars were evaluated: BRS 179, Fundacep and Rubi. The total nitrogen rate was 70 kg ha-1 with 20 kg ha-1 being applied at sowing and 50 kg side-dressed according to the treatment time. Six plant samples were taken to evaluate treatments effects on plant dry mass and tiller production. At each sampling, plants were collected in an area of 0.5 m per plot. The main stem and tillers were separated to determine total dry mass on each structure. Grain yield was determined in an area of 3,2m2. The treatment effects on yield components were assessed harvesting 0.5m of three rows inside each plot. Plants were collected using 0.5m per plot to determine shoot nitrogen uptake (main stem and tillers). A sample of 100g was used to determine kernel nitrogen content when grains were at the harvesting time. The treatment effects on plant and grain N accumulation were assessed harvesting 0.5m of three rows inside each plot. The data were assessed through a Variance Analysis. Means were compared by the Duncan s test at the 0.05 error probability level. The three evaluated cultivars presented different responses in relation to N conversion to dry mass accumulation in the main stem and tillers. Early N application (3,5 Haun s stage) promoted higher tiller production whereas N side-dressing at 5,5 Haun s stage enhanced main stem dry mass accumulation. Late applications performed at 7,5 Haun s stage reduced wheat dry mass partition to tillers. N application at 5,5 promoted the highest values of grain yield. The cultivar Fundacep 36 had the highest production of grains per area and the largest grain yield. Data reported herein indicate that, regardless of cultivar, it is important to side-dress early in the wheat growing cycle because this enhances tiller emission and survival, favoring even growth rates of tillers and the main stem. There was no significant effect of cultivar and time of N fertilization on nitrogen accumulation in the main stem. A negative correlation between kernel protein content and grain yield was detected. In conclusion, tillers were able to accumulate N differently, according to the time of nitrogen side-dress. Nonetheless, such differences were not transported to kernel protein content at harvesting / As cultivares de trigo diferem substancialmente quanto a capacidade de emissão de afilhos, arquitetura de planta e duração do ciclo. Estas diferenças podem interferir na determinação da época ideal de aplicação de nitrogênio em cobertura para otimizar a performance agronômica da cultura. O presente trabalho teve como objetivo identificar os efeitos de época de realização da adubação nitrogenada de cobertura sobre o acúmulo de massa seca no colmo principal e nos afilhos, o rendimento de grãos e componentes e o acúmulo de nitrogênio pelas plantas e o teor protéico dos grãos de três cultivares de trigo. O experimento foi conduzido a campo, durante o ano agrícola de 2003, no município de Lages, SC. Foram testadas quatro épocas de aplicação de nitrogênio em cobertura: estádio 3,5 da escala Haun, estádio 5,5, estádio 7,5 e emborrachamento; e três cultivares de trigo, BRS 179, Fundacep 36 e Rubi. Utilizou-se 20kg.ha-1 de nitrogênio na semeadura e 50kg.ha-1 em cobertura, na forma de uréia. Para avaliar o efeito dos tratamentos sobre o acúmulo de massa seca e a capacidade de afilhamento das cultivares foram realizadas seis coletas de plantas. Em cada época coletou-se plantas numa área de 0,5m lineares de cada parcela. As plantas foram separadas em colmo principal (CP) e afilhos (AF) para obtenção da massa seca (MS) total. O rendimento de grãos foi determinado numa área útil de 3,2m2. Para a determinação dos efeitos dos tratamentos sobre os componentes do rendimento das cultivares, colheu-se 0,5 metro linear de três linhas de cada parcela. Neste material determinou-se a massa de mil grãos, o número de espigas/m2, número de grãos por espiga e o número de grãos/m2. Realizou-se uma coleta de plantas utilizando 0,5m lineares de cada parcela para determinação do nitrogênio total absorvido pela parte aérea (colmo principal e afilhos). Para determinação do conteúdo de nitrogênio nos grãos, utilizou-se uma amostra de 100g de grãos da área útil, quando se encontravam em fase de maturação de colheita. Os dados obtidos foram submetidos à análise de variância. As médias de época de aplicação de N em cobertura e das cultivares foram comparadas pelo teste de Duncan, ao nível de 5% de probabilidade. As três cultivares estudadas responderam diferenciadamente quanto a conversão do nitrogênio em acúmulo de massa seca no CP e afilhos. A aplicação precoce de N (3,5 folhas) estimulou a maior produção de afilhos e a aplicação em 5,5 folhas estimulou mais o acúmulo de massa pelo CP. Aplicações tardias de nitrogênio, realizadas a partir do estádio 7,5, reduziram a alocação de massa seca nos afilhos da cultura do trigo. A aplicação de N em cobertura no estádio de 5,5 folhas propiciou o maior valor de rendimento de grãos. A cultivar Fundacep 36 foi a mais produtiva e também a que apresentou maior número de grãos por área. Independentemente do genótipo, a aplicação precoce (3,5 e 5,5) de nitrogênio foi importante para otimizar o rendimento de grãos da cultura do trigo, pois facilitou a emissão e sobrevivência dos afilhos, bem como promoveu uma taxa de crescimento deste similar a do colmo principal. O teor protéico dos grãos de trigo variou entre 15 e 23% e não foi afetado pela época de aplicação do N. Houve uma correlação negativa entre o teor de proteína nos grãos de trigo na colheita e o rendimento de grãos. Conclui-se, portanto, que há um efeito significativo da época de aplicação do adubo nitrogenado em cobertura sobre a emissão de afilhos e o acúmulo de N pela planta, o qual não se traduziu em diferenças no teor de proteína nos grãos

Fertilized croplands unintentionally export large amounts of reactive nitrogen (N), which degrades water and air quality and contributes to climate change. In this dissertation, I focus on how these reactive N losses are likely to change in the near future as agriculture intensifies in the tropics, and ecological intensification strategies to mitigate N losses are more widely adopted. I use a combination of empirical field measurements in Mato Grosso, Brazil and Skåne, Sweden, literature review, and statistical models to quantify trends. In chapter one, I quantified emissions of nitric oxide (N₂O) and nitrous oxide (N₂O) in forest, single cropped soybean, and N-fertilized double-cropped soybean-maize at three nitrogen fertilizer levels within the largest area of recent cropland expansion on earth, in the Amazon and Cerrado biomes in Mato Grosso, Brazil. I found that NO emissions do not increase when forests are converted to croplands under current fertilization levels, and that NO will respond more strongly than N₂O fluxes to increases in fertilizer applications. In chapter two, I investigated anion exchange capacity and soil nitrate (NO₃¯) pools in deep soils in Mato Grosso, Brazil in the southern Amazon. I found that soil NO₃¯ pools in the top 8 m increased from 143 kg N ha¯¹ in forest to 1,052 and 1,161 kg N ha¯¹ in soybean and soybean-maize croplands. This NO₃¯ accumulation in croplands compared with forest soils matched the estimated amount of surplus N from the croplands, and could be explained by the soil’s positive charge through its anion exchange capacity. In chapter three, I conducted a meta-analysis of the effects of fertilization amount on of NO₃¯ leaching, N₂O emissions, NO emissions, and ammonia (NH₃) volatilization, totaling over 1,000 observations. I found that the relationship between N inputs and losses differed little between temperate and tropical croplands, although total NO losses were higher in the tropics. Among the potential drivers I studied, the N input rate controlled all N losses, but soil texture and water inputs also controlled NO₃¯ leaching losses. In chapter four, I explored the differences in NO₃¯ leaching, fertilizer N use efficiency, and soil N cycling in perennial wheat, which is being domesticated as a more sustainable alternative to annual crops, and annual wheat at a long-term experimental site in Skåne, Sweden. I found that NO₃ leaching was more than two orders of magnitude lower in perennial wheat, overall ecosystem recovery of fertilizer was quite high and not significantly different between perennial and annual wheat after the first growing season, and that measures of soil N cycling were largely the same between both crops. Together, these chapters highlight that reactive N losses will remain a critical global challenge in the coming decades, but that there are also key opportunities to reduce N losses by increasing the use of perennial crops and focusing tropical agricultural intensification on Oxisol soils which buffer against NO₃¯ leaching.

No description available.

Under the conditions of the Rotation Experiment with Fertilizers, the following results were obtained with corn: The phosphorous plat, complete fertilizer plat and the manure plats produced a much higher yield of corn than the check plat. Also, these plats produced a higher percentage of marketable grain than the other plats. There was not much difference in the shelling percentage from the various plats but it was somewhat lower on the nitrogen and the floats plats. The nitrogen-phosphorous plat produced the greatest number pounds of shelled corn per pound of stover. The complete fertilizer plat also produced a high percentage of grain to stover. The percentage of matured ears was greatly increased on the nitrogen-phosphorous plat and the three manure plats. The corn plants on the manure plat developed sooner than those on the other plats while those of the check plat developed later. Also, the plants were larger in circumference and in height on the manured plat. The means of the corn characters were greater on the fertilized plats than on the check plat, and the means increased as the productivity increased. On the whole, the constants of variation were greater on the fertilized plats than on the check plat. The differences were sufficiently great to indicate that they were significant. On the whole, the coefficients of correlation of the corn characters were greater on the fertilized plats than on the check plat but the odds do not show that they are significant. Opposite results were obtained with wheat which is shown in Table 9. Also, in the case of wheat, the odds on the whole are not significant . In summing up all of the data in this experiment, it may be said that manure and acid phosphate were the chief limiting factors affecting yield. High yield of corn is usually accompanied by a high percentage of marketable grain, high shelling percentage, high ratio of grain to stover, high percentage of matured ears, and early maturity of plants. / Master of Science

Rotating wheat with other crops is a common practice in the Willamette Valley of western Oregon. Depending upon previous crop and soil type, current N fertilizer recommendations for wheat in the Willamette Valley vary widely. Excessive fertilizer poses environmental risk, whereas lower N inputs than required by the crop represent economic losses to growers. Growers and their advisors face the challenge to minimize the environmental risk, and at the same time to maintain or increase economic returns. Questions are often raised concerning the efficient use of N fertilizer and accurately predicting the amount of N needed by wheat following different crops. The first study measured growth, N uptake and N use efficiency (NUE) of winter wheat grown after either a legume or oat for three years. In all three growing seasons, winter wheat showed higher biomass, N uptake and NUE when grown after a legume than after oat. The contribution of legume was evident before the wheat was fertilized in spring, indicating that legume N had mineralized in fall or winter. Contribution of soil N to wheat suggested that fertilizer N can be reduced by 44 kg N ha����� if a legume is grown previously. Nitrogen use efficiency estimated 50 to 70 days after N application by isotopic method (24 to 94%) was comparable with that estimated simply by difference (21 to 94%) at the same time. The second study predicted gross mineralization rates using analytical models. Comparable N mineralization was predicted by a model assuming remineralization and a model assuming no remineralization, suggesting that remineralization was negligible. In the spring, mineralization-immobilization turnover was at a lower pace than expected in both rotations. In two growing seasons, gross mineralization rates were higher where the previous crop was legume (0.37 to 0.74 kg����� ha����� day�����) as compared to where oat was grown previously (0.14 to 0.6 kg����� ha����� day). Negative net mineralization indicated that fertilizer N was immobilized in the oat-wheat rotation. The third study evaluated calibration and digestion techniques used to determine elemental concentration in grasses. Use of a dry ashed standard to calibrate the ICP spectrometer generated highly variable calibration curves and was not a viable calibration method. Good agreement was found between chemical and microwave digested standards. Dry ashing resulted in considerable S and Mn losses, whereas, perchloric acid digestion and microwave digestion showed similar results. Our study suggests that if routine analysis are to be performed for macro nutrients or involve trace level work, the best method is microwave digestion with chemical standard calibration of ICP spectrometer. / Graduation date: 1999

No description available.

Recent advances in computer technology have made possible the development of expert systems. Expert systems are computer programs that perform at the level of a human expert. Expert systems can help integrate and apply diverse sources of information and expertise to problems of integrated crop management. A prototype Crop Management eXpert (CMX) system has been developed. The primary goal of CMX is to provide recommendations on optimal irrigation and fertilization scheduling for wheat production in the Pacific Northwest. This system can be used by farmers and/or extension agents. OUS II Shell has been used as a implementation tool. To build this rule - based expert system, a development strategy, commonly used in the construction of expert systems, consisting of 1 ) identification; 2) conceptualization; 3) formalization; 4) implementation; and 5) testing was applied. CMX is composed of modules for irrigation and fertilization management. For irrigation management, CMX is mainly involved in the irrigation scheduling which is the major part of irrigation management. Irrigation strategies have been applied in irrigation decision making. For each strategy, timing criteria which generally consist of management allowed depletion, soil water potential, leaf water potential, and water stress indices have been used. The system provides farmers with irrigation scenarios which determine when and how much water to apply. CMX represents an integration of conventional computing and expert systems technology designed to provide expert recommendations enabling farmers to obtain the best return on their water and fertilizer investment. For fertilization management, a variety of variables have been taken into considered. Crop growth stages, soil moisture, nutrient analysis, protein requirement, and application methods are important factors for the fertilizer decision making. Several constraints have been used in optimal fertilizer advice. CMX can focus only on relevant information, thus reducing the problem space to a manageable size and significantly, improving the efficiency of the system. The facility of the expert system to explain the decision-making process enables users to better understand the underlying assumptions, facts, and reasoning used to generate recommendations. The CMX prototype demonstrates the feasibility of employing expert systems technology in agricultural applications. CMX has been validated and evaluated. The survey results showed that this prototype was successful in capturing domain experts' knowledge as rules and providing advice on the irrigation and fertilization management for wheat. / Graduation date: 1993

Many producers in North America are finding it profitable to make the transition from conventional farming to organic agriculture. Organic fertilisers may affect crop production and soil quality differently than inorganic fertilisers. The objectives of this study conducted in Ste.-Anne-de-Bellevue. Quebec were to examine crop yield, grain quality, soil fertility and microbial community parameters in wheat and corn agroecosystems receiving poultry manure or inorganic fertiliser. Wheat grain yield declined and corn grain yield did not increase with higher N rates, suggesting that increased N supply did not encourage grain production. Soil analyses demonstrated high inherent soil fertility at the study site, and fertilisation led to an environmentally undesirable increase in residual soil NO3 concentrations. Microbial biomass and respiration in corn agroecosystems were greater with poultry manure amendments than inorganic fertiliser, but not in wheat agroecosystems due to significant variation among field replicates. Phospholipid fatty acid analysis revealed significant differences between wheat and corn soil microbial community composition, but differences due to fertilisation were less evident. Further work is needed to uncover the relationships among N fertilisation, crop nutrition and soil microbiology in organic agroecosystems.