Edson Eiji Matsura

Calibração da Reflectometria no Domínio do Tempo (TDR) para a estimativa da concentração da solução no solo

Time Domain Reflectometry (TDR) is a reliable method for in-situ measurements of the humidity and the solution concentration at the same soil volume. Accurate interpretation of electrical conductivity (and soil humidity) measurements may require a specific calibration curve. The primary goal of this work was to establish a calibration procedure for using TDR to estimate potassium nitrate concentrations (KNO3) in soil solution. An equation relating the electrical conductivity measured by TDR and KNO3 concentration was established enabling the use of TDR technique to estimate soil water content and nitrate concentration for efficient fertigation management.

Avaliação de sondas de TDR multi-haste segmentadas para estimativa da umidade do solo

The knowledge of soil water content is important for agriculture, mainly the determination of its changes in the soil profile in order to optimize irrigation management. The tendency to use the technique of TDR (Time Domain Reflectometry) to measure the soil water content is relatively new in Brazil. To help the diffusion of this technique, the objective of this work was to study the possibility of using multi-wire probes with electrical impedance discontinuities in TDR equipment. The experiment was divided in to two parts. In the first one, the laboratory performance of two multi-wire probe configurations was studied; and in the second one, the evaluation of the probe reliability to monitor water content changes in porous media. The viability of the use of multi-wire probes to estimate the water content in the porous media profile was confirmed. However, the use of a probe with 0.10 m segmentation was limited to the soil depth of 0.40 m, due to the difficulty to interpret the impedance peaks at the extremity.

Comparison of Methods to Quantify Organic Carbon in Soil Samples from São Paulo State, Brazil

Soil carbon (C) determinations are important for soil quality assessment. The standard method that is used in São Paulo state to determine soil organic C is a modified Walkely–Black method. This method has some disadvantages because of the time needed for implementation and the use of potassium dichromate. Therefore, the aims of this work were to test the efficiency and compare the following methods: (a) wet oxidation of organic C (OC-HO) followed by spectrophotometer determination, (b) dry incineration at 550 °C with a muffle furnace plus gravimetric determination (TC-I), and (c) dry combustion with a C–nitrogen (N)–sulfur (S) elemental analyzer (TC-EA). Sixty-one soil samples were collected at the 0- to 20-cm depth on agricultural soils of São Paulo state. Samples were dried at 65 °C, ground, and sieved through a 0.09-mm sieve. Carbon content was determined in triplicate. These sets of samples exhibited a wide range of C content: TC-EA was from 0.43 to 9.14 g 100 g−1. Mean C contents were 6.76 g 100 g−1, 2.31 g 100 g−1, and 2.52 g 100 g−1 for TC-I, OC-HO, and TC-EA, respectively. Moreover, in all the studied soil samples, the TC-I method overestimated the C content when compared with OC-HO and TC-EA methods. Losses of structural water and inorganic colloidal compounds, such as gibbsite, induced by high temperature during incineration probably were responsible for the greater C contents obtained by the TC-I method. Correlation coefficients between the three methods were rather similar: TC-I and TC-EA (r = 0.87), TC and OC-HO (r = 0.83), and TC-EA and OC-HO (r = 0.84). It was concluded that C extraction by the standard, routinely employed OC-HO method can be replaced by the TC-EA method, which has environmental advantages.

Multi-wire time domain reflectometry (TDR) probe with electrical impedance discontinuities for measuring water content distribution

The adequate estimation of water content distribution in wetted volume is fundamental in determining the number of drippers per plant and their location below the plant canopy in drip irrigation. Measurements of water content distribution are usually made by opening trenches, which is a time-consuming method and sometimes imprecise. Recent scientific developments have created the possibility of monitoring the soil moisture content using electronic sensors. The objective of this research was to develop and test two multi-wire time domain reflectometry (TDR) probes with electrical impedance discontinuities (referred to as the multi-wire probe) for sensing soil profile water content distribution. The experiment was divided in two parts. In part one, the laboratory performance of two multi-wire probe designs was studied and their reliability to monitor the water content variation in a porous media profile was evaluated. The second part was conducted in a 250 l bucket and the soil water content distribution, for an application depth of 15 mm, was evaluated by monitoring over 6 days at discharge rates of 2 and 4 l h-1. The results demonstrated the viability of using multi-wire probes to estimate soil water content distribution with different probe designs and to consistently obtain water content measurement in water dynamic processes. The following conclusion may drawn from the main results: (1) The measured characteristic impedance of the multi-wire probe for different designs was not the same as that geometrically calculated. This was due to the non-ideal probe geometry which provoked signal loss, thus, hindering peak impedance interpretation, mainly for probe 1 design. (2) The use of multi-wire probes in the TDR equipment showed a speedy determination of soil profile water content distribution using a single measurement. Author Keywords: Time-domain reflectometry; Probe design; Wetted volume; Drip irrigation

Consumo de água e produção de grãos do feijoeiro irrigado em sistemas plantio direto e convencional

The inappropriate use of water resources in agriculture, to get higher yields, has caused negative impacts on soil water storage, reducing the efficiency of irrigated productive systems. The aim of this research was to study water use through crop coefficients for sprinkler-irrigated beans at different development stages, in addition to the production of grains and their components, in no tillage and tillage crop systems. Irrigation management was monitored with tensiometers to maintain the soil water content level between 28% (at the moment of irrigation) and 31% (field capacity). The crop evapotranspiration level (ETc) was obtained from the soil water balance and the reference evapotranspiration (ETo) using the Penman-Monteith method. The results indicate that bean crop coefficients show lower values in the no tillage system than in the conventional tillage system, during flowering and pod formation stages. The bean plants in no tillage system are more efficient in relation to water use than the conventional tillage system, because in this system, the bean crop shows higher grain yield with lower water consumption.

Teores de nutrientes na alface irrigada com água residuária aplicada por sistemas de irrigação

Desenvolveu-se este trabalho para avaliar a composicao quimica da parte aerea da alface, cv. Elisa, irrigada com agua residuaria tratada com leitos cultivados com macrofitas e agua de um deposito de fonte hidrica superficial, cultivada em Latossolo Vermelho Distroferrico, utilizando-se dos sistemas de irrigacao por aspersao convencional, gotejamento subterrâneo e superficial. O experimento compreendeu o periodo de 17-8 a 3-10-2001, e as analises quimicas da alface foram realizadas aos 47 dias apos o transplantio das mudas em campo. A parte aerea da alface foi analisada quanto ao teor de nitrogenio total, nitrato, fosforo, potassio, calcio, magnesio, enxofre, ferro, manganes, cobre, zinco, sodio, boro, cobalto e molibdenio. O sodio e o enxofre apresentaram teores maiores que o maximo adequado na parte aerea da alface e o magnesio menor, enquanto para os demais elementos quimicos foram normais e adequados, considerando os padroes para plantas bem nutridas, nao sendo influenciados pelo tipo de agua. O sodio foi o elemento quimico que apresentou a maior elevacao na parte aerea nos tratamentos irrigados com agua residuaria, apresentando diferenca significativa em relacao a agua do deposito superficial nos tres sistemas de irrigacao. A utilizacao dos diferentes sistemas de irrigacao para aplicacao de agua residuaria tratada com leitos cultivados com macrofitas nao interferiu no teor de nutrientes na parte aerea.

Distribuição da água no solo para o dimensionamento da irrigação por gotejamento

The principal objective of a drip irrigation system design is to choose the appropriate layout and components to obtain adequate distribution of water (and fertilizer) throughout the field. Based on this the contributions which are capable of furmishing the basic elements for the design of drip irrigation were evaluated using the TDR probes. The experiment was divided into two parts. In the first part, the effect of successive irrigations on the wetted volume (horizontal and vertical dimensions) were analyzed under laboratory conditions; and in the second one, the water infiltration and distribution processes were evaluated with respect to formation of the wetted volume in the field. It was concluded that: initial soil water content, applied volume, discharge rate, saturated disk and hydraulic conductivity are important elements and these must be known for an appropriate irrigation design and management.

Uniformidade de distribuição de água em pivô central, com a utilização da técnica TDR na superfície e no interior do solo

A avaliacao da uniformidade de distribuicao de agua de um sistema de irrigacao e feita acima da superficie do solo. Tendo em vista a importância da uniformidade no interior do solo quando submetido a uma irrigacao, desenvolveu-se o presente trabalho com o objetivo de se avaliar a uniformidade de distribuicao de agua, tanto acima como no interior do solo, atraves dos coeficientes CUD e CUC, com um pivo central operando em condicoes de campo. Acima da superficie, a uniformidade foi obtida seguindo-se a metodologia da Associacao Brasileira de Normas Tecnicas (ABNT) e se alocando duas linhas de coletores com abertura de 3o, a partir do ponto inicial do pivo. Propos-se, para obtencao da uniformidade no interior do solo, a utilizacao da umidade determinada pelo TDR (Reflectometria no Dominio do Tempo) visto que e uma tecnica simples e produz resultados imediatos. Os resultados encontrados demonstraram que a uniformidade no interior do solo foi maior que na superficie, ficando acima da faixa recomendada, mostrando que a redistribuicao da agua no interior do solo promove maior uniformidade de umidade no perfil do solo que a encontrada na lâmina aplicada; portanto, no dimensionamento economico de sistemas de irrigacao, os coeficientes de uniformidade obtidos no interior do solo devem ser considerados.

Altura da lâmina, tempo e volume de enchimento de um equipamento de irrigação por pavio e determinação da uniformidade de distribuição de água em substratos

The aims of this study were to evaluate the water depth, filling time and volume in a wick irrigation equipment using auto compensating gutters and to determine the water distribution uniformity (WDU) in these equipments filled with organic com mercial substrates (pine bark/PB and coconut coir/CC). We assembled two experimental modules in a completely randomized design with five replications. There was variation in water depth measurements (1.6 to 4.0 cm), even with the equipment lev eled. Average filling time was 6h22min for Module 1 with PB and 3h45min for Module 2 with CC. The filling volume was vari able, showing that gutters in the extremities (No. 1 and 5) had lower volumes in Module 1 and in the beginning (No. 1 and 2) in Module 2. Volumetric soil moisture (Ɵ) ranged from 42 to 94% in Module 1 and from 24 to 72% in Module 2, with isolated points of desiccation and/or flooding. Water depth, filling time and volume were disuniform in all experimental modules and auto compensating gutters, indicating equipment imperfections. Water distribution was variable in both substrates due to their hydro-physical characteristics and also water depth in the gutters, with higher humidity and water distribution uniformity in pine bark than in coconut coir.

Root system distribution of sugarcane irrigated with domestic sewage effluent aplication by subsurface drip system

Irrigation with domestic sewage effluent (DSE) has been recommended by subsurface dripping, as it can obtain a high rate of irrigation efficiency and faster use of salts in comparison with other irrigation methods. The study aimed at evaluating the area, the length and the effective depth of the root system of sugarcane irrigated with DSE by subsurface drip system and with different irrigation rates at depths of 0.00-0.20, 0.20-0.40, 0.40-0.60 and 0.60-0.80m. The experiment was carried out in the municipality of Piracicaba, in the state of Sao Paulo (SP), Brazil, in a sugarcane area irrigated with DSE in a completely randomized blocks set up in furrows, with three replications and four treatments, which are: one area without irrigation (AWI) and three irrigated areas meeting 50% (T50%), 100% (T100%) and 200% (T200%) of the crops water need between each round of irrigation. T100% and T200% provided smaller areas and lengths of roots in the two deepest layers, as compared to AWI and T50%, which stimulated the development of deeper roots due to the water stress. TWI, T100% and T200% presented 80% of the roots up to a depth of 0.40m and T50% treatment presented 76.43% of roots total.