Development and Evaluation of Pedotransfer Functions to Estimate Soil Moisture Content at Field Capacity and Permanent Wilting Point for South African Soils

This study was undertaken to develop new pedotransfer functions (PTFs) for the estimation of soil moisture content at field capacity (FC, at −33 kPa) and permanent wilting point (PWP, at −1500 kPa) for South African soils based on easily measurable soil physico-chemical properties. The new PTFs were developed using stepwise multiple linear regressions with the dependent variable (either FC or PWP) against clay, silt, sand and soil organic carbon (SOC) content from a total of 3171 soil horizons as the explanatory variables. These new PTFs were evaluated and compared with five well-established PTFs using a total of 3136 soil horizons as an independent dataset. The coefficient of determination (r2) values for the existing PTFs ranged from 0.65–0.72 for FC and 0.72–0.81 for PWP, whilst those developed in this study were 0.77 and 0.82 for FC and PWP, respectively. The root mean square error (RMSE) values for the well-established PTFs ranged from 0.052–0.058 kg kg−1 for FC and 0.030–0.036 kg kg−1 for PWP, whilst those developed in this study were 0.047 and 0.029 kg kg−1 for FC and PWP, respectively. These findings suggest that PTFs derived locally using a large number of soil horizons acquired from different agro-climatic locations improved the estimation of soil moisture at FC and PWP. Due to the range of conditions and large soil datasets used in this study, it is concluded that these new PTFs can be applied with caution in other regions facing data scarcity but with similar soil types and climatic conditions.

Comparison of the physical properties of soils belonging to different reference soil groups

Soil properties can be influenced by long-term agricultural management practices as described in pedological literature. In this study, selected physical properties (particle density and bulk density, total porosity, maximum capillary water capacity, minimum air capacity, field capacity, permanent wilting point and available water capacity) of topsoils from different reference soil groups (Cambisols, Luvisols, Fluvisols, Chernozems and Phaeozems, Leptosols, Stagnosols and Gleysols) were sampled and analysed in the years 2016–2017. The topsoil samples were taken from points of so-called S (specific) soil pits to be sampled from the General Soil Survey of Agricultural Soils (GSSAS) which was accomplished in the years 1961–1970. In addition, some of the properties were also compared with those measured during the GSSAS. Recognising the properties, only the particle density, the maximum capillary water capacity, the permanent wilting point and the available water capacity of the topsoil of the individual soil groups were statistically significantly (P < 0.05) different. A comparison of the physical properties with those analysed after more than 40 years was performed, the bulk density increased and the total porosity decreased in the topsoil of the major part of the studied soil groups.

Effects of Soil Conditions on Root Rot of Soybean Caused by Fusarium graminearum

Fusarium graminearum is an important soybean pathogen that causes seedling disease, root rot, and pre- and postemergence damping-off. However, effects of soil conditions on the disease are not well understood. The objective of this greenhouse study was to determine the impacts of soil texture, pH, and soil moisture on seedling root rot symptoms and detrimental effects on seedling development caused by F. graminearum. F. graminearum-infested millet was added (10%, vol/vol) to soil with four different textures (sand, loamy sand, sandy loam, and loam). Soil moisture was maintained at saturation, field capacity or permanent wilting point at soil pH levels of 6 or 8. Seedlings were evaluated 4 weeks after planting for root rot, root length, root and shoot dry weights, leaf area, and F. graminearum colonization (by qPCR). There was a significant interaction between soil moisture and soil texture for root rot assessed visually (P < 0.0001). Highest severity (67%) and amount of F. graminearum DNA were observed at pH 6 and permanent wilting point in sandy loam soils. Pot saturation resulted in the lowest levels of disease in sandy loam and loam soils (11.6 and 10.8%, respectively). Reductions in seedling growth parameters, including root length, foliar area, shoot and root dry weights, and root tips, relative to the noninfested control, were significantly greater in sandy loam soils. In contrast, there were no significant growth reductions in sand. This study showed that levels of root rot increased under moisture-limiting conditions, producing detrimental effects on plant development.

Effects of Arbuscular Mycorrhiza Fungi and Coffee Pulp Compost in Improving Soil Water Uptake by Chilli Around the Permanent Wilting Point Conditions

Soil water availability to the plants is a range of water content between the field capacity and the permanent wilting point (PWP) conditions. The PWP is defined as the lower limit of soil water content that the plant can extract water from the soil as indicated by the symptoms of wilting plants. This is because plant roots are unable to penetrate the soil micropores that contain the water. The study aims to analyze the effects of arbuscular mycorrhizal fungi (AMF) and compost in enhancing soil water absorption by the plant when the water content is close to the permanent wilting point. Four doses of AMF (0, 5, 10 and 15 g.plant-1) and three doses of coffee pulp-made compost (0, 5 and 10 ton.ha-1) were arranged according to a randomized complete block design with three replicates. Results showed that the application of AMF significantly enabled the plant to improve water uptake when the soil water content was about at the permanent wilting point conditions. The AMF addition of 15 g.plant-1 significantly prolonged the growing period of chili to wither and the plant showed the wilting symptoms at the soil water content of 5 to 7% lower than the no-AMF plants. Improved water uptake under water stress conditions was attributed to increases in the root colonization by AMF.

ATRIBUTOS FÍSICO-HÍDRICOS DO SOLO VIA FUNÇÕES DE PEDOTRANSFERÊNCIA EM SOLOS DOS TABULEIROS COSTEIROS DE PERNAMBUCO

ATRIBUTOS FÍSICO-HÍDRICOS DO SOLO VIA FUNÇÕES DE PEDOTRANSFERÊNCIA EM SOLOS DOS TABULEIROS COSTEIROS DE PERNAMBUCO FERNANDA HELENA NASCIMENTO DE ANDRADE1; CERES DUARTE GUEDES CABRAL DE ALMEIDA2; BRIVALDO GOMES DE ALMEIDA3; JOSÉ AUDIFAX CÉZAR DE ALBUQUERQUE FILHO1; BRUNO CAMPOS MANTOVANELLI4 E JOSÉ COELHO DE ARAÚJO FILHO5 1 Departamento de Engenharia Agrícola, Programa de Pós-Graduação em Engenharia Agrícola da Universidade Federal Rural de Pernambuco - UFRPE, Rua Dom Manuel de Medeiros, S/N, Dois Irmãos, CEP: 52171-900, Recife, PE, Brasil, [email protected], [email protected] 2 Colégio Agrícola Dom Agostinho Ikas, Programa de Pós-Graduação em Engenharia Agrícola da Universidade Federal Rural de Pernambuco - UFRPE, Rua Dom Manuel de Medeiros, S/N, Dois Irmãos, CEP: 52171-900, Recife, PE, Brasil, [email protected]. 3 Departamento de Agronomia, Programa de Pós-Graduação em Ciência do Solo da Universidade Federal Rural de Pernambuco - UFRPE, Rua Dom Manuel de Medeiros, S/N, Dois Irmãos, CEP: 52171-900, Recife, PE, Brasil, [email protected]. 4 Departamento de Ciências Rurais, Programa de Pós-Graduação em Ciência do Solo da Universidade Federal de Santa Maria - UFSM, Avenida Roraima, n° 1000, Camobi, CEP: 97105-900, Santa Maria, RS, Brasil, [email protected]. 5 Empresa Brasileira de Pesquisa Agropecuária, EMBRAPA Solos - UEP Recife, Rua Antônio Falcão, n° 402, Boa Viagem, CEP: 51020-240, Recife, PE, Brasil, [email protected]. 1 RESUMO Objetivou-se gerar funções de pedotransferência (FPT) com base em dados das frações granulométricas, distribuição do tamanho de poros, densidade do solo e de partículas para estimar a umidade do solo equivalente à capacidade de campo (CC), ponto de murcha permanente (PMP) e a capacidade de armazenamento de água disponível (CAD) em Argissolos Amarelos representativos dos tabuleiros costeiros na zona da mata norte de Pernambuco. Para isso, foram coletadas amostras deformadas e indeformadas na camada 0,00 - 0,20 m de profundidade. As FPTs foram geradas a partir do método de regressão linear múltipla aplicando a técnica de stepwise backward. Este método eliminou alguns atributos físico-hídricos do solo baseado nos valores de R2 e no Teste t. Os coeficientes de regressão do modelo proposto para predição de CAD, CC e o PMP apresentaram significância de 1% de probabilidade para as variáveis independentes selecionadas para cada modelo, indicando que esses parâmetros podem ser preditos, com ótima precisão, a partir do conteúdo de areia, argila, mesoporosidade, microporosidade e densidade do solo, as quais são fáceis de serem determinadas e obtidas, pré-requisito básico para construção das FPTs. Palavras-chave: manejo de irrigação, stepwise backward, índices estatísticos. ANDRADE, F. H. N.; ALMEIDA, C. D. G. C.; ALMEIDA, B. G.; ALBUQUERQUE FILHO, J. A. C.; MANTOVANELLI, B. C.; ARAÚJO FILHO, J. C. SOIL PHYSICAL-HYDRIC PROPERTIES BY PEDOTRANSFER FUNCTION IN SOILS OF COASTAL PLAINS OF PERNAMBUCO 2 ABSTRACT Aimed to generate pedotransfer functions (PTF) based on particle size, pore size distribution, soil and particle density to estimate the field capacity (CC), permanent wilting point (PMP) and available water capacity (CAD) in Ultisol Typic Fragiaquults in coastal plains of Pernambuco. Thus, deformed and undeformed samples were collected at 0.00 - 0.20m depth. PTFs were generated from multiple linear regression method by stepwise backward technique. This method eliminated some hydro-physical soil attributes, based on the values of R2 and t test. CAD, CC and PMP estimated values showed a significant correlation of 1% probability for independent variables selected for each model. Thus, available water capacity, field capacity and permanent wilting point can be predicted with great precision by sand, clay content, mesoporosity, microporosity and soil density, which are easy to determine and obtain, basic prerequisite for construction of PTFs. Keywords: irrigation management, stepwise backward, statistical indexes.

Development and Evaluation of a Drip Irrigation System in Southeastern Nigeria

Extreme climatic factors (temperature, precipitation etc) which at times lead to drought and flooding affect crop yield negatively. In this study, a PVC drip irrigation was developed and the irrigation parameters were evaluated in a farmland with three tillage methods (conventional tillage, conservative tillage and no tillage). The irrigation treatments comprised of three levels of irrigation (50% Management allowable depletion, 30% management allowable depletion and 10% management allowable depletion). Different irrigation parameters were evaluated for different crop growth stages, different soil treatments and different soil depths (0-25 cm, 25-50, 50-75 and 75-100 cm depths). The field capacity was determined at -0.01MPa, from the result, the field capacity was minimum at no tillage (0.07 cm3/cm3, 0.11 cm3/cm3, 0.12 cm3/cm3, and 0.14 cm3/cm3) for soil depths 0-25 cm, 25-50 cm, 50-75 cm and 75-100 cm respectively, for conservative tillage (0.11 cm3/cm3, 0.11 cm3/cm3, 0.11 cm3/cm3, 0.14 cm3/cm3) for 0-25 cm, 25-50 cm, 50-75 cm and 75-100 cm soil depths respectively and conventional tillage (0.09 cm3/cm3, 0.13 cm3/cm3, 0.15 cm3/cm3, 0.17 cm3/cm3) for 0-25 cm, 25-50 cm, 50-75 cm and 75-100 cm soil depths respectively. The permanent wilting point was determined at -1.5MPa, from the result, permanent wilting point increased with increase in soil depth in conventional tillage and no tillage with PWP of 0.01 cm3/cm3, 0.05 cm3/cm3, 0.09 cm3/cm3 and 0.11 cm3/cm3 at 0-25 cm, 25-50 cm, 50-75 cm and 75-100 cm soil depths respectively for conventional tillage and PWP of 0.02 cm3/cm3, 0.05 cm3cm3, 0.05 cm3/cm3 and 0.08 cm3/cm3 at 0-25 cm, 25-50 cm, 50-75 cm and 75-100 cm soil depths respectively for no tillage. The average net irrigation was found to be 1.2 cm, 1.56 cm and 1.95 cm for conventional tillage, conservative tillage and no tillage respectively, while the average gross irrigation was found to be 1.7 cm, 1.7 cm and 2.1 cm for conventional tillage, conservative tillage and no tillage respectively. Statistical analysis of net and gross irrigation gave a coefficient of determination of 0.99 and p-value at 0.05 was significant with a value of 0.00007.