Spatial and temporal variability of Eh and pH over a rice field as related to lime addition

Abstract

The aim of this study was to describe the effect of lime additions on the spatial variability of pH and Eh in a typic Plintacualf cultivated with rice, in Corrientes, Argentina. The 5.1 ha field was divided in three sub plots at which dolomitic lime additions were made at the rates zero, 625 kg ha -1 and 1250 kg ha -1 . The soil was sampled at three stages: before sowing thus in aerobic conditions, and then two more times in anaerobiosis. Ninety-six samples per sub plot were taken on each of the three sampling stages on a grid of 11.9 x 20 m. Soil pH and Eh were measured by routine methods. The pH values increased, whereas Eh values decreased, following flooding. The coefficients of variation for pH was rather low during all the three studied periods. Conversely, the CV values for Eh were initially low but with a sharp increased in the second sampling date. The spatial variability of the studied soil properties was assessed using semivariogram analysis and examination of the maps constructed with values interpolated with kriging. Soil pH exhibited a rather strong spatial dependence, whereas soil Eh had a strong to moderate spatial dependence all over the three studied periods and for the three lime rates. Spherical models reaching a stable sill with low to moderate nugget effect were fitted to the experimental semivariograms for the 18 data sets (3 subplots, 3 liming rates and 2 properties) studied. Spatial variability of pH and Eh on rice fields was far from negligible both on aerobic and on anaerobic conditions. In general pH exhibited a stronger spatial dependence than Eh and also showed a tendency to present smaller ranges of spatial dependence. Contour maps clearly showed the presence of small scale variability for pH and Eh within each liming treatment and during each of the three sampling dates. Neither pH or Eh had temporal stability of the pattern of spatial distribution on field studied.Key Words: semivariogram, flooded field, liming, kriging. RESUMO VARIABILIDADE ESPACIAL E TEMPORAL DO PH E EH DO SOLO SOB CULTIVO DE ARROZ EM RELAÇÃO À ADIÇÃO DE CALCÁRIOO objetivo deste trabalho foi descrever o efeito da adição do calcário na variabilidade espacial de pH e Eh, em um Typic Plintacualf cultivado com arroz, em Corrientes, Argentina. O campo de 5.1 ha foi dividido em três subparcelas onde foram efetuadas aplicações de calcário dolomitico nos níveis zero, 625 kg ha -1 e 1250 kg ha -1 . Amostras de solo foram coletadas em três estágios: antes da semeadura (condição anaeróbica), e duas outras amostragens em condições anaeróbicas. Noventa e seis amostras por sub parcela foram coletadas em cada um dos três estágios em grade de 11.9 x 20 m. O pH e o Eh do solo foram determinados nas amostras de solo pelos métodos de rotina. Os valores de pH aumentaram enquanto os de Eh diminuiram após a inundação. Os coeficientes de variação para pH foram muito baixos durante todos os três períodos estudados. Por outro lado, os CV para Eh foram inicialmente baixos mas tiveram aumento drástico a partir da segunda amostrag...

Evaluation of Factors Influencing the Groundwater Chemistry in a Small Tropical Island of Malaysia

“…On the other hand, pH shows negative loading, which is likely influenced by the increase in DOC from runoff and leached from sewage, making the Eh reaction in the area dependent on the pH. A similar relationship between redox and pH was also reported by Morales et al [47]. PC2 indicates a weak loading of turbidity, which can be explained by the fact that turbid water contains organic matter that would eventually attract microorganisms.…”

Spatial Distribution and Temporal Variability of Ammonium-Nitrogen, Phosphorus, and Potassium in a Rice Field in Corrientes, Argentina

“…Three successive sampling campaigns were carried out to assess the stability of the spatial distribution along the growing season of the studied soil properties. Results reported on previous work for pH and Eh [ 17 ] and for extractable Fe, Mn, and Zn [ 12 ] showed a rather strong seasonality in the spatial distribution of these variables with changing patterns between sampling dates. Seasonal stability of nutrient maps has been considered as a prerequisite for efficient precision agriculture management [ 20 ].…”

“…The study was conducted on a paddy field located near Corrientes, Argentina, cropped to rice ( Oryza sativa , L.). The experimental site and the sampling procedure have been described before [ 12 , 17 ] and therefore this information will be briefly summarized here. The climate is warm, subtropical with mean temperature of 20.1°C and mean yearly rainfall of about 1200 mm.…”

“…More recently, the value of spatial measurements of soil properties coupled with geostatistical techniques to develop site specific management practices also has been widely acknowledged [ 2 , 9 , 10 ]. Indeed, geostatistical analysis has been carried out to assess heterogeneity in paddy soils, focussing either on soil properties and/or crop yield [ 5 , 11 ] or on soil properties and/or nutrients [ 12 – 17 ].…”

“…Seasonal stability of nutrient maps has been considered as a prerequisite for efficient precision agriculture management [ 20 ]. On the other hand, several soil properties and nutrient in paddy soils previously have been shown to vary along the rice growing period [ 12 , 17 , 22 , 24 , 25 ]. Therefore, the first objective of this study was to conduct a field-scale analysis of the spatial variability of ammonium-N and available phosphorus and potassium, using the unpublished data sets of the above mentioned trial.…”