Synthetic Polymers on Water Retention and Pore Distribuition in a Clayey Latosol

Abstract

Abstract:The use of polymers is increasing at the agricultural area, however their effects on soil porosity have been little studied. The objective of this article is to analyze the effects of applied synthetic polymers on soil porosity and water retention of a Dystroferric Red Latosol. This study was conducted on undisturbed samples collected at a depth of 0.05 m in a Latosol beneath native forest. The samples were saturated with distilled water and polymers HyC, HyA, HyB diluted in water according to use recommendations for coffee plantations. These samples were then submitted to matric potentials of -2, -4, -6 and -10 kPa in the suction units and -33, -100, -500 and -1500 kPa in a Richards extractor. The models were fitted and pore size distribution estimates calculated. The data were subjected to variance analysis and the averages were compared using the Scott-knott test to a level of 5 %. Decreasing of large pores volume than 145 µm, was detected with the application of polymers HyA and B. However the HyB polymer promoted a reduction in the pore volume in the intermediate classes (2.9-0.6; 0.6-0.2 µm), that are responsible for water availability to plants. On the other hand the HyC polymer promoted an increase in the soil water retention.Keywords: soil porosity; synthetic polymers; soil water availability.RESUMO: O uso de polímeros é crescente no meio agrícola, porém seus efeitos na porosidade do solo são pouco estudados. O presente trabalho teve como objetivo analisar os efeitos da aplicação de polímeros sintéticos na porosidade e retenção de água de um Latossolo Vermelho Distroférrico muito argiloso. O estudo foi realizado em amostras indeformadas coletadas na profundidade de 0,05 m, em um Latossolo sob mata nativa. Amostras foram saturadas com água destilada e com os polímeros HyC, HyA, HyB diluídos em água conforme recomendações de uso para cultura do cafeeiro. Em seguida estas amostras de solos foram submetidas a potenciais matriciais de -2, -4, -6 e -10 kPa nas unidades de sucção e -33, -100, -500 e -1500 kPa nas câmaras de Richards. Foi realizada a modelagem de curvas de retenção de água e calculada a distribuição de poros por tamanho. Os dados foram submetidos a análises de variância e as médias comparadas pelo teste de Scott-knott ao nível de 5 %. Houve uma redução do volume de poros da classe de tamanho > 145 µm quando o solo foi saturado com os polímeros HyA e HyB. O polímero HyB promoveu uma redução do volume de poros das classes intermediárias (2,9-0,6; 0,6-0,2 µm), responsáveis pela disponibilidade de água para as plantas. Já o polímero HyC promoveu o aumento da retenção de água no solo.Palavras-chave: porosidade do solo; polímeros sintéticos; disponibilidade de água no solo.

Crop coefficients of tropical forage crops, single cropped and overseeded with black oat and ryegrass

“…Since the soil water balance was cumulative, in the start of spring, there may have been a soil water deficit, soon met by irrigation. Furthermore, Benevenute et al (2016) claim attention is necessary to avoid errors when managing the soil moisture.…”

“…The irrigation water depth (LI) applied was determined by the ETc measured by the lysimeters. Volumetric soil moisture at field capacity (q fc ) considered corresponded to the soil water matric poten-tial Ψ m = 10 kPa, according to Benevenute et al (2016). Current soil moisture (q c ) as a function of Ψ mc (current soil water matric potential) was calculated by mean values of the soil water retention curve, obtained from a tension table and by a Richards extractor, in a laboratory of soil and water quality analyses adjusted by the van Genuchten equation (van Genuchten, 1980):…”

Autonomous Soil Water Content Sensors Based on Bipolar Transistors Encapsulated in Porous Ceramic Blocks

“…Next, the sensor was inserted in a clayey red latosol with the following composition: 0.65 kg kg −1 clay, 0.21 kg kg −1 silt, and 0.14 kg kg −1 sand; and a second test was carried out to measure its output as a function of small differences in matric potentials. When the water retention curve of this soil was measured for small matric potentials between 1 kPa and 35 kPa, a practically linear behavior was observed [23].…”

Yield parameters and water productivity of tropical and overseeded winter forages

“…The previously established irrigation interval was based on a 70% limit of the water availability factor. The moisture at field capacity (θfc) was considered to be the moisture corresponding to the value of the matrix potential, Ψm = 0.1 bar (Benevenute et al 2016). The values of current moisture (θc) were estimated by means of the soil water retention curve, which was obtained with the aid of a tensor…”