Land degradation and soil nutrient depletion have become serious threats to agricultural productivity in sub-Saharan Africa. Soil fertility depletion in smallholder areas has been cited as the fundamental biophysical cause of declining per-capita food production in Africa. Manure application is a well established and known practice, but not effectively used among South African smallholders. This study investigated the practice, constraints and perceptions of improving soil quality through manure application through a case study of three smallholder farmer groups. Three groups from rural areas of KwaZulu-Natal (Mkhambatini, Mooi River and Richmond) were selected to participate in the study. Participatory methodologies were used to identify and clarify the study problem. Three participatory focus group discussions, one per area, were conducted with farmers at the study sites to discuss farming methods, experience and perceptions of manure use, manure management practices and constraints farmers experience with manure use. Force Field Analysis was used for each group to explore for forces against and in support for manure use. Random soil and manure samples were collected for laboratory analysis to determine fertility levels. Some farmers indicated that soil fertility was low. However, half the sample perceived the land to be productive to some extent. The study showed that 40 per cent of farmers reported improved soil fertility following the application of manure. Due to the limited availability of livestock manure, farmers prefer to use both livestock manure and commercial fertilisers. Furthermore, the study found that except for young farmers (20 per cent of the sample), farmers had not received formal training and very limited extension advice on composting and manure use and management. The study participants were aware of the consequences of declining soil fertility and were attempting to improve soil quality. However, low livestock numbers and poor management led to inadequate amounts of manure, and, limited access to information on manure and compost use. Unless better knowledge of optimal soil nutrient management practice is acquired by the farmers, soil fertility levels will continue to decline, further reducing production potential and rural household food security. Government needs to revisit extension support to meet the needs of smallholders and offer training on sound soil management, sustainable production methods, composting and livestock management. A handbook with graphic detail should be accompanied to provide smallholders with information and advice on how to manage soil fertility. / Thesis (M.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

Diss. Umeå : Sveriges lantbruksuniv.

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

Made available in DSpace on 2016-06-02T19:29:23Z (GMT). No. of bitstreams: 1 3063.pdf: 3377110 bytes, checksum: fda162bf60bb5679d2f8f4cfb07989b1 (MD5) Previous issue date: 2010-05-06 / Considered as alternative management more appropriate for tropical conditions, the no-tillage system can follow the principles of organic agriculture and contribute to the evolution and sustainability of organic cotton production systems. In order to generate usage information about soil covering plants for white and colored cotton fibers production in the organic system with no-tillage, an experiment was conducted in the farming years 2006/07 and 2007/08 in Cáceres-MT, with randomized block design, treatments disposed in scheme of split plots and four replicates. In the plots, were evaluated soil coverage consisting of crop residues of Estilozobium aterrimum, Cajanus cajan, Canavalia ensiformes, Crotalaria juncea, Pennisetum glaucum cv ADR 300, Sorghum bicolor cv BRS 307, mixture of species used, spontaneous vegetation and exposed soil. In the sub plots were evaluated upland cotton cultivars BRS ITAUBA (white) and CNPA AMT 19 (brown) in no-tillage on the crop residues of the soil covering plants cultivated in pre-planting. The plant coverage produces phytomass in sufficient quantities for adequate soil coverage. The Estilozobium aterrimum, in a general manner, shows greater extraction capacity and accumulation of nutrients, high lighting the potential cycling of nitrogen and phosphorus, while Pennisetum glaucum and Crotalaria show, respectively, greater potential cycling of potassium and magnesium. The crop residues of Canavalia ensiformes, spontaneous vegetation and Crotalaria provide low persistence coverage, while Pennisetum glaucum residues and Cajanus cajan provide more persistent coverage. During the process of residues decomposition, the nutrients following this descending order of release: K > P > N = S > Mg > Ca, being the potassium the nutrient with faster release and subject to losses. The Estilozobium aterrimum shows greater weed suppression capacity, showing potential for use in production system without application of herbicides, in contrast with the low suppression capacity of Pennisetum glaucum plants and spontaneous vegetation. The contribution of plant coverage residues promote on the surface layer of soil increases in values of attributes pH, MOS, P, K, Ca, Mg, V e CTC. The coverage does not influence the characteristics of fibers, but exerts significant effects on agronomic characteristics and productivity of cotton. The highest yield occurs in straws of Crotalaria juncea, Canavalia ensiformes, Estilozobium aterrimum and mixture of species. The cotton cultivars of brown fiber (CNPA AMT 19) shows productivity and quality of fiber lower than the cultivars of white fiber (BRS ITAÚBA), however has fibers with characteristics that meet the standards required by the textile industry. / Considerado como alternativa de manejo mais adequada para as condições tropicais, o sistema plantio direto pode seguir os princípios da agricultura orgânica e contribuir para a evolução e sustentabilidade dos sistemas de produção orgânica de algodão. Com o objetivo de gerar informações sobre o uso de plantas de cobertura de solo para a produção de algodão de fibras brancas e coloridas no sistema orgânico com plantio direto, foi conduzido um experimento nos anos agrícolas 2006/07 e 2007/08 em Cáceres-MT, com delineamento de blocos casualizados, tratamentos dispostos em esquema de parcelas subdivididas e quatro repetições. Nas parcelas avaliaram-se coberturas de solo constituídas por resíduos culturais de mucuna preta (Estilozobium aterrimum), feijão guandu anão (Cajanus cajan), feijão de porco (Canavalia ensiformes), crotalária juncea (Crotalaria juncea), milheto (Pennisetum glaucum cv ADR 300), sorgo granífero (Sorghum bicolor cv BRS 307), coquetel das espécies utilizadas, vegetação espontânea e solo exposto. Nas subparcelas avaliaram-se as cultivares de algodoeiro herbáceo BRS ITAÚBA (branco) e CNPA AMT 19 (marrom) em plantio direto sobre os resíduos culturais das plantas de cobertura de solo cultivadas em pré-plantio. As plantas de cobertura produzem fitomassa em quantidades suficientes para uma adequada cobertura de solo. A mucuna preta, de modo geral, apresenta maior capacidade de extração e acúmulo de nutrientes, destacando-se quanto ao potencial de ciclagem de nitrogênio e fósforo, enquanto o milheto e a crotalária apresentam, respectivamente, maior potencial de ciclagem de potássio e magnésio. Os resíduos culturais do feijão de porco, vegetação espontânea e crotalária proporcionam coberturas de baixa persistência, enquanto os resíduos de milheto e guandu anão proporcionam coberturas mais persistentes. Durante o processo de decomposição dos resíduos, os nutrientes seguem a seguinte ordem decrescente de liberação: K > P > N = S > Mg > Ca, sendo o potássio o nutriente de liberação mais rápida e sujeito a perdas. A mucuna preta apresenta maior capacidade de supressão de plantas invasoras, evidenciando potencial para uso em sistemas de produção sem aplicação de herbicidas, contrastando com a baixa capacidade de supressão do milheto e da vegetação espontânea. O aporte de resíduos de plantas de cobertura promove na camada superficial do solo aumento nos valores dos atributos pH, MOS, P, K, Ca, Mg, V e CTC. As coberturas não influenciam nas características de fibras, mas exercem efeitos significativos nas características agronômicas e na produtividade de algodão. As maiores produtividades ocorrem nas palhadas da crotalária juncea, feijão de porco, mucuna preta e coquetel de espécies. A cultivar de algodão de fibras marrom (CNPA AMT 19) apresenta produtividade e qualidade de fibra inferior à da cultivar de fibra branca (BRS ITAÚBA), porém suas fibras possuem características que atendem os padrões requeridos pela indústria têxtil.

In the last decade, the adoption of technologies in corn crop provided a significant productivity and yield increase in Sergipe State, Brazil. In this state, soils classified as Inceptisols are very adequate for corn cropping. The only limitation presented by those soils is the low levels of available P for plants. Fertilization to increase soil P level through rock phosphates should be considered in order to increase P response to annual P fertilization in the row, which is related to the crop requirement. On the other hand, direct application of rock phosphates in soils which have pH (H2O) above 5,5 and a high calcium content, like those above mentioned, has not been recommended because they could slow down the dissolution of rock phosphates. A strip split plot in a complete randomized blocks design with four replications experiment, was set up in order to study the agronomic effectiveness of Bayóvar and Itafós rock phosphates applied for soil P correction in an Inceptisol with pH 6,0 and high calcium content. Rock phosphates and triple superphosphate, used as a reference source, were broadcasted in the main plots and incorporated by disk plowing. A main plot without soil P correction also was included in the study. In the subplots annual P application at rates of 0, 60 e 120 kg.ha-1 as triple superphosphate were accomplished in the planting rows. Corn was grown in the raining seasons of 2011 and 2012. Yield and P leaf content indicated that less P from annual application was needed in treatments corrected by those sources with higher P solubility. Mehlich-1 and mixed resin method removed more soil P from rock phosphates plots than the reference TSP plot. The relative agronomic effectiveness (RAE) of Bayóvar and Itafós rock phosphates were 77,19% and 45,66%, respectively, calculated based on two years. / Na última década, a modernização da tecnologia de cultivo do milho no Estado de Sergipe proporcionou significativos aumentos de produção e produtividade. Neste sentido, as áreas de Cambissolos vêm se destacando por serem muito adequadas a esta cultura, apresentando limitações somente quanto aos níveis de P. Uma das formas para contornar a baixa disponibilidade deste nutriente no solo pode ser a realização de uma adubação corretiva através de fontes fosfatadas alternativas de baixo custo e/ou solubilidade. Esta prática visa elevar o teor de P disponível no solo com a finalidade de propiciar uma melhor resposta da cultura às doses de P aplicadas no sulco de plantio. Desta forma, foi conduzido um experimento de dois anos para avaliar a eficiência agronômica dos fosfatos de Bayovar e Itafós, como fontes corretivas de P, em um Cambissolo Háplico Ta Eutrófico vertissólico, de elevado teor de cálcio trocável e pH em torno de 6. O delineamento experimental utilizado foi em blocos ao acaso, com parcelas subdivididas em faixas, e quatro repetições. As parcelas consistiam das adubações corretivas realizadas no primeiro ano com as fontes Fosfato Natural Reativo de Bayóvar, Fosfato de Rocha Itafós e superfosfato triplo (fonte de referência), na dose de 200 kg ha-1 de P2O5, e um tratamento sem correção. As subparcelas foram compostas pelos três níveis de adubação de manutenção, no sulco de plantio, aplicados anualmente através de superfosfato triplo, nas doses de 0, 60 e 120 kg.ha-1 de P2O5. No período avaliado, a produtividade de grãos e o teor de P na folha do milho indicaram menores necessidades de reposição de P para as plantas, conforme maior era a solubilidade da fonte corretiva aplicada ao solo. Com relação à determinação de P disponível no solo, tanto Mehlich-1 quanto a Resina de Troca Iônica removeram mais P do solo dos tratamentos em que os fosfatos naturais foram aplicados. O índice de eficiência agronômica médio dos fosfatos para os dois anos foi de 77,19 % e 45,66 % para o Bayóvar e Itafós, respectivamente.

MSCAGR (Soil Science) / Department of Soil Science / The application of organic manures as alternatives to reduce the use of mineral fertilizers is considered a good agricultural practice for smallholder farmers. However, the effect of organic manure on soil properties and crop yield depends upon its application rate and chemical composition. Climatic seasonal variability within the study area could adversely affect crop production. The amount of rainfall and temperature are among the most important factors that determines crop production. This field experiment was carried out during the 2013/2014 and 2014/2015 cropping seasons at the University of Venda experimental farm which is located about 2 km west of Thohoyandou town in the Vhembe District, Limpopo Province. The main objective of this study was to determine the effect of three types of organic manure (cattle, poultry and their combination (1:1)) on yield and water use efficiency of sunflower (Helianthus annuus L.) and selected soil physical and chemical properties under rainfed conditions. The experiment was a randomized complete block design (RCBD) with four treatments and four replications (control (C0), cattle manure (CM), poultry manure (PM) and their combination (CM + PM)). All organic manures were applied 21 days before planting at a rate equivalent to 20 t ha-1. The manures were incorporated in the soil using a hoe to an approximate depth of 10 cm. Crop water use (WU) and water use efficiency (WUE) were determined using the water balance equation. Rainfall was measured using three standard rain gauges installed on the experimental site. Change in soil moisture storage was determined by monitoring soil moisture content weekly using a neutron water meter (NWM), calibrated on the experimental site. Data on sunflower dry matter and leaf area index (LAI) was collected at flower bud stage, flowering stage and at grain maturity stage. Plant height and stem girth were also determined at the same developmental stages. Grain yield was measured at physiological maturity. xv Analysis of variance (ANOVA) was carried out using SPSS software. Due to seasonal variability encountered during the two cropping seasons, particularly in terms of rainfall, further analysis of two factors (viz. cropping season and organic manure) and their interaction were performed. The differences between treatment means were separated using the least significant differences (LSD) procedure. The results showed that organic manure application had no significant effect on soil physical properties. Poultry manure application resulted in lowest bulk density (BD) with a decrease of 32% in the top layer (0 – 20 cm) compared to control. Cattle manure + PM and CM application decreased BD in the top layer by 14% and 9% compared to control, respectively. Poultry manure and CM recorded almost the highest similar stable aggregate fractions at all soil depths. Poultry manure recorded the highest final infiltration rate and cumulative infiltration followed by CM and CM + PM. The control treatment retained the highest mean water content compared to other treatments at both field capacity (FC) and wilting point (WP). Cattle manure + PM and PM recorded the least mean water content among others at FC and WP respectively. This could be as a result of increased micropores by organic manure application on a clayey soil which allowed an ease movement of water that control treatment which had no manure application. Total N, Ca, and Zn were significantly different between treatments in the first cropping season while K, Na, CEC and Zn were significantly different in second cropping season. pH recorded no significant difference in all treatments in both cropping seasons. CM + PM recorded the highest OC at top layer (0 – 20 cm) in both cropping seasons compared to other treatments. Dry matter yield and LAI at flower bud, flowering and maturity stages increased with the application of different manures compared to the C0. Organic manure application showed a significant (p<0.05) effect on dry matter at all growth stages in the second cropping season. Organic manure had a significant effect on LAI only at flower bud stage of the first cropping season, with PM and CM + PM recording the highest similar value of 1.31. The manure xvi application also showed a significant (P<0.05) effect on plant height and stem girth at all growing stages in the second cropping season, whereas in the first cropping season the significant effect was only in the flower bud stage for both parameters. Grain yield was significantly affected by the manure application in the second cropping season. Manure application in the second cropping season resulted in an increase in the grain yield compared to the first cropping season, except for PM where the grain yield decreased significantly by 167.92% from the first cropping season. Then high grain yield in the second cropping season could be as a result of high WUE reported. The manure application had a significant effect (p<0.05) on water use efficiency (WUE) in the second cropping season. The WUE recorded the highest values under CM and CM + PM treatments in second cropping season than in first cropping season, while PM recorded the highest WUE value in the first cropping season. Generally, organic manures used obtained higher grain yield and WUE compared to control. Keywords: Organic manure, smallholder farmers, sunflower and water use efficiency