M. S.

A field experiment was conducted in the Ridge and Valley region of Virginia near Blacksburg during the 1989 through 1991 corn-rye growing seasons. The treatments in this experiment consisted of varying amounts of ¹⁵N-depleted fertilizer N applied to corn (Zea mays L.) at planting followed by a winter rye (Secale cereale L.) cover crop treatment. The research was divided into four studies. The first study was conducted to evaluate an analytical procedure that could be used for the diffusion of low masses of ¹⁵N-labeled NH₄ in 2M KCI and subsequent analysis for N recovery and ¹⁵N concentrations in soil by direct combustion mass spectrometry. Diffusion was found to be a suitable technique for preparing low-mass N samples for automated ¹⁵N analysis by Automated Nitrogen-Carbon Analysis/Mass Spectrometry (ANCA/MS). Recoveries of low masses of added N were quantitative, and accurate ¹⁵N concentrations were obtained when the results were corrected for isotope dilution due to background or contaminant N. The second study was conducted to determine if ¹⁵N-depleted fertilizer N could be satisfactorily used as a tracer of residual fertilizer N in plant tissue and various soil N fractions through a corn-winter rye crop rotation. Fertilizer-derived N in the soil NO₃-N fraction following corn harvest was clearly detectable and distinguishable from natural abundance to a 90-cm depth. Detection of fertilizer N in the total N pool below the 30-cm depth was not reliable, particularly at the lower N rates. Clay-fixation of fertilizer N measured at corn harvest was not detected by ¹⁵N analysis. Inconclusive results indicate that further research is needed to determine the feasibility of using depleted material for measuring clay-fixation of fertilizer-derived NH₄⁺-N. Nitrogen uptake by a winter rye cover crop reduced soil NO₃-N levels below that required for accurate isotope-ratio analysis. Following winter fallow (approx. 1 yr after fertilizer application) residual ¹⁵N-depleted fertilizer N was still detectable in plant tissue and the soil NO₃-N fraction. The objectives of the third study were to measure plant uptake and soil distribution of fertilizer N applied to corn at varying N rates and to determine the relationships between economic optimum N rate, fertilizer-use efficiency, and potential leaching loss of residual fertilizer N to groundwater. Plant recovery of fertilizer N in 1989 ranged from 33 to 47% even though no grain yield and fertilizer N uptake response resulted from N fertilization. Greatest accumulation of residual fertilizer N was found in the surface 30-cm both years following corn harvest. The economic optimum N rate for 1990 corn planted into a rye mulch (218 kg N ha⁻¹) corresponded closely with the rate (224 kg N ha⁻¹) resulting in the highest fertilizer-use efficiency. Low levels of residual fertilizer-derived NO₃ in the 60-90-cm depth following the 1990 corn harvest provides evidence to support the use of the economic optimum N rate concept from both economic and environmental viewpoints. The fourth study was designed to measure the effectiveness of a winter rye cover crop for recovering residual fertilizer N from the previous application of varying N rates to corn. Recovery of fertilizer N by winter rye increased with increasing N rate applied to the previous corn crop and ranged from 3.5 to 35.9 kg N ha⁻¹ in 1990 and 2.3 to 25.7 kg N ha⁻¹ in 1991. Residual fertilizer N recovery in 1991 was higher in rye plots where the previous corn crop had been planted no-till into rye stubble as compared to corn planted no-till into rye mulch. Little or no fertilizer-derived mineral N was measured in the soil to a final depth of 90-cm following a winter rye cover crop. Amounts of fertilizer-derived mineral N increased with depth and previous fertilizer N rate applied to corn following winter fallow. These results provide evidence to support the use of a winter rye cover crop on a silt loam soil to recover residual fertilizer-derived mineral N that might otherwise be lost to groundwater. / Ph. D.

Call number: LD2668 .T4 1985 J638 / Master of Science

Sustainable agriculture in China is highly threatened by rapid urbanization, land degradation and high population pressure. Yunnan Province, south-west China, is 94% mountainous and lacks flat land. Food shortages and inappropriate cultivation have led to intensive cultivation of steep, marginal and fragile land and have increased soil erosion. To curb this situation and assist with poverty alleviation, it is crucial to develop more productive and sustainable cropping systems. An experiment was conducted on sloping areas from 1999 to 2001 in Wang Jia Catchment, Yunnan Province. The project aim was to evaluate the effects of five selected cultivation practices on maize productivity and soil properties. The treatments were: (1) downslope cultivation without mulch, (2) contour cultivation without mulch, (3) contour cultivation with polythene mulch, (4) contour cultivation with polythene and wheat straw mulch (Integrated Contour with Plastic and Straw Mulch Treatment, INCOPLAST) and (5) contour cultivation with polythene mulch and intercropping, wide and narrow row spacing, with soybean in wide row spacing. Crop growth parameters and soil physical properties were measured throughout the cropping seasons. Considering three years data, contour cultivation with polythene mulch generally increased soil temperature by a mean of 1-2°C. The polythene retained considerably more soil moisture during dry weather. However, during wet weather, polythene prevented rainfall directly falling on the soil, which led to less soil moisture content. The soil temperature and moisture regimes under polythene mulch made plants grow faster and canopies develop well, leading to higher final yields. The benefit of polythene was 33-54% more yield than downslope cultivation without mulch treatment, over three seasons. Contour cultivation plus polythene and straw mulch retained significantly higher soil moisture levels. The yield of this treatment in 1999 was ranked second, but in 2000 it had the highest yield and in 2001 it was also more effective than contour cultivation with polythene mulch treatment. Contour cultivation with polythene mulch and intercropping improved maize yield. The soybean harvest also contributed to net income, the crop had a similar function to straw mulch and increased N availability. Contour cultivation increased yields over the range 7.2-11.2% over three seasons compared with downslope cultivation, equivalent to ~500-1000 kg per hectare more grain produced. There were few clear trends in soil properties over the 1999-2001 period. However, N concentrations increased in the contour cultivation with polythene mulch and intercropping treatment. Both contour cultivation with polythene and straw mulch and contour cultivation with polythene mulch and intercropping gave apparent increases in total K, probably resulting from both decayed straw and decomposed soybean leaves. In terms of simple cost-benefit evaluation, downslope cultivation had the lowest input and output, while contour cultivation had a similar input, but a higher output. Contour cultivation with polythene had the highest net return. Contour cultivation with polythene and straw had a high output but did not give a higher net return than contour cultivation with polythene. Contour cultivation with polythene mulch and intercropping generally had the highest input and output and could give a higher net return than contour cultivation with polythene when the soybean harvest was successful, but over three years this treatment had the greatest risk from crop failure. It is recommended that replacing downslope cultivation with contour cultivation can increase crop yields and this simple action could contribute to the development of more sustainable cropping systems in Yunnan. Polythene mulch achieved higher maize yields but its environmental impact requires further study. It is considered that contour cultivation with polythene and straw mulch or soybean intercropping could contribute towards more productive and sustainable cropping systems where soil conservation is high priority. The technique could assist with long-term soil, water and nutrient conservation and improved crop productivity.

Thesis (DTech (Faculty of Applied Sciences)--Cape Peninsula University of Technology, 2009 / A 3-factorial experiment involving two cowpea densities (83,000 and 167,000 plants.ha-1), two cropping systems (i.e. monoculture and mixed culture) and five cowpea genotypes (i.e. three farmer-selected cultivars, Bensogla, Sanzie and Omondaw and two improved varieties, ITH98-46 and TVu1509) was conducted in the field for two consecutive years in 2005 and 2006. The aim was to assess the effect of plant density, cropping system and cowpea genotypes on: (i) chlorophyll and gas-exchange, (ii) rhizosphere mineral concentration and tissue uptake of nutrients, (iii) acid and alkaline phosphatase activities in the rhizosphere, (iv) plant growth and symbiotic performance, and (v) concentration of flavonoids and anthocyanins in seed extracts and plant organs and their effect on pest infestation and diseases. The results showed that high plant density (167,000 plants.ha-1) and mixed culture significantly decreased gas-exchange parameters, leaf chlorophyll content, 13C and %C in both cowpea and sorghum plants compared with low plant density (83,000 plants.ha-1) and monoculture. The data also showed significantly higher 13C and lower %C in ITH98-46 and TVu1509 compared with Bensogla, Omondaw and Sanzie genotypes with a significant correlation between 13C and water-use efficiency. At harvest, grain yield of cowpea and sorghum was significantly decreased by high plant density and mixed culture compared with low plant density and monoculture. Sanzie genotype was generally superior in grain yield (2,550 kg.ha-1) followed by cvs. Omondaw and Bensogla (2,250 and 2,150 kg.ha-1, respectively) compared with the improved cultivars. Sorghum plants in mixture with cv. TVu1509 or cv. ITH98-46 performed better (1,570 and 1,550 kg.ha-1, respectively) compared with those in mixture with other cultivars. The results also showed greater land equivalent ratio (LER = 1.42 to 1.52), suggesting that mixed culture produced greater total yields per unit land area compared with monoculture.

Cabbage is one of the most important and widely grown crops in KwaZulu-Natal (KZN). In cabbage production, no clear cropping methods exist (other than succession cropping) to allow the soil to recover its fertility status naturally after the harvested has crop absorbed nutrients from the soil. Succession cropping system is extensively practiced by cabbage farmers. Succession cropping is when a succeeding vegetable crop is planted immediately after harvesting the preceding crop. This does not allow soil fertility status to be balanced by soil microbes in an environmentally friendly approach. Instead, synthetic fertilizers are heavily used to rectify soil fertility status and these have negative impacts on the soil in the long term, followed by yield decline. However, the economic downturns and green environment awareness have caused researchers and some farmers to focus more on developing environmentally healthy crop production technologies. A priority in this study was to elucidate effects of cover crops-green manure as rotational crops in cabbage production. The experimental site is located at Cedara Research Station. In 2009, soil samples were taken from the top 30 cm of the soil profile, in a zigzag pattern in 5 m x 5 m grids for fertility analysis. Results were used to determine nutrient deficiencies, and blanket application of phosphorus and potassium followed according to each grid’s deficiency. The study was divided into two cycles, with each cycle consisting of season one and season two. The study was conducted over a two year period. Cycle one, season one, 2009/2010 (Dec-Mar): four treatments (sunn hemp: planted at 50 kg/ha seeding rate; forage sorghum: planted at 50 kg/ha seeding rate; mixture of sunn hemp-forage sorghum: each planted at 25 kg/ha seeding rate and control: cabbage planted at 30 cm within rows x 60 cm between rows) were used. The statistical design of the study was a 4x4 Latin Square experiment repeated twice in adjacent fields (347 m2 each) 6 m apart, with a total of 32 plots. Each experimental plot was 8.5 m x 9 m. Genstat Package, 9th Edition was used for data analysis. Standard cabbage production recommendations were followed in control treatments. Cabbage yield was determined in all control plots. Weed coverage percentages were determined in all four treatments. Cycle one, season two, 2010, (Apr-Aug): all 32 plots from season one were each split into four, in a Split Plot design, resulting in a total of 128 plots in both fields. Nitrogen was applied at four different levels: 0, 80, 160 and 240 kg N/ha. Standard cabbage production methods were followed again as in the control treatment in season one. Cover crops were replaced by planting cabbage. Cabbage was repeated in the control plots. Cabbage yield, cabbage leaf nutrients, soil nitrate and ammonium nitrate and soil carbon to nitrogen (C:N) ratio were measured. Cycle two, season one, 2010 (Sep-Dec): The same method in cycle one, season one was repeated. Cycle two, season two, 2010/2011, (Dec-Apr): The same method in cycle one, season two was repeated. Although in this study there was visibly a large amount of residues left over after the trial was harvested, the use of a tractor-drawn slasher was not very effective. The slashed material was not chopped into smaller pieces, as it would if a roll-chopper had been used. A tractor-drawn slasher was used because it is a tool available to many farmers. As a result, it was not a simple process to transplant seedlings mechanically, due to the amount of organic matter that was in the soil after it had been incorporated. The mechanical planter pulled off, removed and became blocked by the residues, and as a result it was not able to operate as it would in normal soils. The residues removed soil from the furrows and that caused seedlings to fall over as all the soil for the root system support had been moved by the planter and stuck residues. The planter had to be assisted by hand planting seedlings that were not properly planted mechanically. Hence, from the operational perspective, the choice of tools for chopping were not effective in this study and this is something to be considered in future studies, where it will be necessary to compare different tools for planting and cover crop incorporation into the soil. During the present study, soil N content in different plots had significant differences (P=0.05). The control showed high levels of total N content, but this was not related to the low yields exhibited by cabbage after cabbage at all levels of N. Since, where there were cover crops, the N content was low, this could mean that N was immobilized, compared to the cabbage treatments where plenty of N was available. Immobilized N is thus not available for leaching, polluting the environment. The yield of cabbage was significantly lowest in controls. The study showed that cover crop-green manure use has a positive effect in terms of yield improvement. The cabbage yields from the sunn hemp plots at a 0 kgN/ha were significantly different from the yield of cabbage planted following cabbage at 240 kgN/ha N. The study also showed that N is not the only yield determinant in cabbage production. Too much N has a tendency to suppress cabbage yields. The cover crop-green manures selected for this study were shown to be ineffective in suppressing weeds. This was true even though the weed coverage percentage in each of the cover crop-green manure plots was above 65%, except for the cabbage crop. This study did not separate different weeds, but the most dominant weeds were Amaranthus hybridus (pigweed), Galinsoga parviflora (gallant soldier), Bidens pilosa (common blackjack) and Cyperus esculentus (yellow nutsedge). These weeds were effectively controlled in the cabbage sole crop by the use of herbicides and mechanical weeding. The result of cover crop-green manures not suppressing weeds was significantly associated with the cover crop-green manure seeding rate. This study has been a starting point in the development of cover crops-green manure as rotational crops in cabbage production. It is concluded that cover crop-green manure (sunn hemp and forage sorghum) used in this study for vegetable (cabbage) production has proven to be successful in improving yields. Yields obtained from cover crop-green manure treatments were better than yields obtained from - conventional tillage methods for cabbage production (control). However, in cabbage, weed suppression and soil N content, failed to improve significantly in response to the cover crop green manures used. The high plant population density under a cover crop, combined with weed population, may lead to high uptake of soil N for plant growth, leaving less N in the soil and in the plant. In the sole cabbage crop, because of low competition, there was adequate uptake of N for plant growth and yet the crop was not exhaustive of soil N. Further research is required in the following areas: comparison of cabbage with other vegetable crops in response to the effect of the selected cover crops; comparison of mechanical weeding and herbicide use as means of controlling weeds during cover crop-green manure growth; identification of dominant weeds in the presence and absence of cover crops, and monitoring of soil water relations and other fertiliser effects. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 4 uppsatser.

Submitted by MATHEUS SARAIVA BIANCO null (matbianco2004@yahoo.com.br) on 2016-01-15T20:04:26Z No. of bitstreams: 1 TESE DOUTORADO MATHEUS BIANCO.pdf: 1015406 bytes, checksum: a764665f12062dbcf01f07c520fbf038 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-01-18T16:13:35Z (GMT) No. of bitstreams: 1 bianco_ms_dr_jabo.pdf: 1015406 bytes, checksum: a764665f12062dbcf01f07c520fbf038 (MD5) / Made available in DSpace on 2016-01-18T16:13:35Z (GMT). No. of bitstreams: 1 bianco_ms_dr_jabo.pdf: 1015406 bytes, checksum: a764665f12062dbcf01f07c520fbf038 (MD5) Previous issue date: 2015-12-21 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O cultivo consorciado de hortaliças é um sistema de produção alternativo à monocultura, e quando manejado adequadamente pode incrementar o lucro da atividade agrícola e diminuir impactos ambientais. Foi realizado um experimento com o objetivo de avaliar o efeito de épocas de transplante do espinafre em consórcio com a couve, sobre a produtividade das culturas e o índice de eficiência do uso da área (EUA). O delineamento utilizado foi de blocos casualizados, com 17 tratamentos e quatro repetições. Os tratamentos constaram da combinação dos fatores: sistema de cultivo (consórcio e monocultura) e épocas de transplante do espinafre (0, 14, 28, 42, 56, 70, 84 e 98 dias após o transplante (DAT)) em relação à couve. Foram utilizadas as cultivares ‘Top Bunch’ (couve) e ‘Nova Zelândia’ (espinafre). As produtividades totais (PT) e por colheita (PC) da couve em monocultura não diferiram das obtidas em consórcio, independente da época de transplante do espinafre. A PT do espinafre foi influenciada pela época de transplante, sendo maior quanto mais cedo foi o transplante. A PC do espinafre somente foi influenciada pelo sistema de cultivo, sendo que em cultivo solteiro a PC foi cerca de 27% maior do que em cultivo consorciado. O índice de eficiência do uso da área não foi influenciado pela época de transplante, e teve valor médio de 1,71, indicando a viabilidade do consórcio. Os índices Coeficiente de Competitividade, Agressividade, Perda de Produtividade e Vantagem do Consórcio mostraram que, independente da época em que o espinafre for transplantado, a couve é a espécie dominadora e espinafre a dominada. O custo operacional total de um hectare do consórcio de couve e espinafre ‘Nova Zelândia’ é de R$ 13.049,23, enquanto um hectare de couve e do espinafre ‘Nova Zelândia’, em monoculturas, são de R$ 12.797,22 e R$ 10.418,90, respectivamente. / The intercropping of vegetables is an alternative production system to monoculture, and when handled properly can increase the income of agricultural activity and reduce environmental impacts. An experiment was conducted in order to evaluate the effect of spinach transplant times in consortium with kale on crop productivity and the area use efficiency index (USA). The design was a randomized block with 17 treatments and four replications. Treatments consisted of a combination of factors: cropping system (intercropping and monoculture) and Spinach transplant times (0, 14, 28, 42, 56, 70, 84 and 98 days after transplanting (DAT)) relative to kale. The cultivars 'Top Bunch' (kale) and 'New Zealand' (spinach) were used. The total productivity (TP) and productivity per harvest (PH) of kale in monoculture did not differ from those obtained in consortium, regardless of spinach transplant time. The spinach PT was influenced by the time of transplant, the higher the transplante. The Spinach PH was only influenced by the cropping system, and PH was about 27% higher monoculture than in intercropping. The area use efficiency index was not affected by the time of transplant, and had average value of 1.71, indicating the consortium’s viability. The Coefficient Competitiveness, Aggressiveness, Productivity Loss and Consortium Advantage showed that, regardless of the time when the spinach is transplanted, kale is the dominant species and the spinach dominated. The total operating cost of one hectare of kale and 'New Zealand' spinach consortium is R$ 13,049.23, while one hectare of kale and 'New Zealand' spinach in monoculture cost R$ 12,797.22 and R$ 10,418.90, respectively. / CNPq: 140617/2012-4

Orientadores: Carlos Roberto Espindola, Marlene Cristina Alves / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-07T05:40:21Z (GMT). No. of bitstreams: 1 Carvalho_JoseaneCarinaBorgesde_M.pdf: 4092551 bytes, checksum: 7db0785f360c7cf4341ce58b1534c898 (MD5) Previous issue date: 2006 / Resumo: Este estudo trata do processo de degradação da estrutura do solo sob diferentes condições de uso, a partir da análise da estabilidade dos agregados e análise microbiológica, aliados a análises de rotina, como a distribuição granulométrica e complexo sortivo, carbono e pH, além da densidade e porosidade do solo. Os diferentes usos dos solos estudados foram: substrato degradado, substrato degradado com aplicação de lodo, solo com pastagem, substrato com vegetação regenerada (capoeira) e solo sob cerrado. Os tratamentos que sofreram degradação estão inseridos em uma grande ¿área de empréstimo¿, no município de Selvíria (MS), onde está instalada a Fazenda de Ensino e Pesquisa da UNESP do Campus de Ilha Solteira/SP, ao lado da Usina Hidrelétrica de Ilha Solteira. Todos os tratamentos sem lodo revelaram baixa fertilidade dos solos, em função dos teores de bases, matéria orgânica e CTC, além de processos de compactação mecânica, com altos valores de densidade associados. O emprego do lodo de esgoto no substrato degradado imprimiu mudanças consideráveis nos solos. A análise de agregados mostrou altos percentuais de componentes estruturais nas classes de menores tamanhos, muito adensados, em consonância com a porosidade e a densidade. A aplicação de lodo de esgoto provocou melhora no substrato degradado, com aumento do percentual de agregados nas classes de tamanho maiores, aliado à diminuição da densidade. Os solos com pastagem e cerrado, em ambientes menos impactados, apresentaram maior estabilidade dos agregados nas classes de tamanhos maiores, em decorrência da ação de suas vegetações, promovendo constantes aportes de material orgânico. A biomassa microbiana e a contagem de bactérias atestaram que os tratamentos foram fortemente influenciados pela quantia e qualidade de material orgânico fornecido, constituindo exemplo sensível a melhoria das condições do substrato degradado, por exemplo, a biomassa microbiana, dentre os solos degradados, ou com lodo aplicado, ultrapassando, nesse quesito, a qualidade do solo degradado que já regenerou uma capoeira. Outro exemplo dessa eficiência foi observado na pastagem, em que as gramíneas proporcionaram valores mais pronunciados na contagem das bactérias do que no solo sob cerrado, confirmado também na estabilidade dos seus agregados, ressaltando a importância da rizosfera das gramíneas para o fornecimento de exsudatos como fonte de energia e nutrientes para a comunidade bacteriana. Assim, a condição dos agregados associada à constituição microbiológica mostraram-se nitidamente dependentes das práticas de manejo dos solos envolvidos, com resultados muito benéficos trazidos pela aplicação de material orgânico, no caso, o lodo de esgoto / Abstract: The aim of this study was the evaluation of the degradation processes of soil structure under different cropping systems, with aggregate stability analysis and microbial biomass activities allied to soil routine analysis, like granulometric evaluation and sorption complexes, carbon, pH, density and soil porosity. Different cropping systems evaluated in study area were: degraded substrate, sludge added in degraded substrate, pasture soil, regenerated plants soils (underbrush) and scrubland. Treatments that suffered degradation are inserted in a wide-range ¿lending area¿, in Selvíria municipality, Mato Grosso do Sul state, where is established Unesp's Fazenda de Ensino e Pesquisa - Ilha Solteira Campus, besides Ilha Solteira powerplan. In different studied cropping systems, all treatments without the use of sewage sludge showed low fertility, characterized by low base supplies, organic matter and CEC. The use of sewage sludge in the degraded substrate showed considerable changes in soils. Aggregated stability analysis were efficient in changing detection by cropping systems in soil structures. High aggregate percentages were detected in degraded treatment in small size classes, very thick, as seen on porosity and density analysis, with substantial improvements in degradated substrate with sludge, which shows high aggregated percentage in large size classes, allied to lower densities. Pasture and scrubland soils in less impacted environments, showed more aggregated stability on the large size classes, due to its vegetation action, promoting constant furnishing of organic material. Microbial biomass activities showed, by microbial determination and bacterial counts, that treatments were strongly dependent by quality and quantities of available organic matter, this is an sensible example of an upgrade of a degraded substrate. For example, microbial biomass in the substrate degradated, soil with sludge was better, in this point, on the quality of degradated soil and underbrush soil. Other efficiency example was observed by grass species, which proportionate more acceptable values compared to stunted vegetation soils regarding bacterial counting, that reflects in soil aggregate stabilities in this treatment, confirmed the grass rizosphere importance in supplying the energy and nutrient sources to microbial biomass. Therefore, the aggregated condition associated to the microbiological constitution showed up clearly dependent on the cropping systems of the involved soils, with results very positives brought by the application of organic material, sewage sludge, in this case / Mestrado / Análise Ambiental e Dinâmica Territorial / Mestre em Geografia