Tahei Yamamoto

Assessment of evapotranspiration estimation models for use in semi-arid environments

Abstract Limited information exists on reliable estimates of evapotranspiration (ETo), to be used as forecasts, to achieve high irrigation water use efficiency in semi-arid environment, particularly under microirrigation (MI) system. The objectives of this study were to: (i) assess the estimates of ETo obtained using six models against experimentally determined values in a semi-arid environment, Karaj in Iran; (ii) assess the usefulness of short-term weather data in the computation of ETo estimates for forecasting purposes; and (iii) compare ETo computed for a semi-arid environment with that of a humid temperate environment, Tottori in Japan. In-field lysimeter experiments were conducted in 1993 and 1994 in Karaj to compute daily ETo from water-balance data and a similar experiment was conducted in 1972 and 1973 in Tottori. The ETo estimates were obtained using the Penman (PE), Penman–Monteith (PM), Wright–Penman (WP), Blaney–Criddle (BC), Radiation balance (RB), and Hargreaves (HG) models. The ETo forecasts for Karaj and Tottori were obtained using 5- or 8-year weather data and 1- and 2-year return period approach. Compared with the lysimeter values, over- and underestimations of ETo, by all six models, were a norm in Karaj. Nevertheless, the PM model produced the best ETo estimates as assessed by root mean square, mean bias error, and t-test statistics for the semi-arid Karaj, whereas the PE model performed best for the temperate Tottori. In general, the ETo forecasts obtained using 8-year weather data were better than 5-year weather data. The 2-year return period ETo forecasts were better than 1-year return period, regardless of the duration of weather data duration. The results show that: (i) PM model produced best ETo estimates for semi-arid environment whereas the PE model produced the best ETo estimates for humid temperate environment; and (ii) 8-year weather data and 2-year return period approach produced most reliable ETo estimates for forecasting purposes.

Effects of Zeolite on Soil Nutrients and Growth of Barley Following Irrigation with Saline Water

ABSTRACT Soil salinity is a major abiotic factor limiting crop production but an amendment with synthetic zeolite may mitigate effects of salinity stress on plants. The objective of the study was to determine the effects of zeolite on soil properties and growth of barley irrigated with diluted seawater. Barley was raised on a sand dune soil treated with calcium type zeolite at the rate of 1 and 5% and irrigated every alternate day with seawater diluted to electrical conductivity (EC) levels of 3 and 16 dS m−1. Irrigation with 16 dS m−1 saline water significantly suppressed plant height by 25%, leaf area by 44% and dry weight by 60%. However, a substantial increase in plant biomass of salt stressed barley was observed in zeolite-amended treatments. The application of zeolite also enhanced water and salt holding capacity of soil. Post-harvest soil analysis showed high concentrations of calcium (Ca2 +), magnesium (Mg2 +), sodium (Na+), and potassium (K+) due to saline water especially in the upper soil layer but concentrations were lower in soils treated with zeolite. Zeolite application at 5% increased Ca2 + concentration in salt stressed plants; concentrations of trace elements were also increased by 19% for iron (Fe2 +) and 10% for manganese (Mn2 +). The overall results indicated that soil amendment with zeolite could effectively ameliorate salinity stress and improve nutrient balance in a sandy soil.

Nitrogen recovery of coated fertilizers and influence on peanut seed, quality for peanut plants grown in sandy soil

ABSTRACT Warm and high precipitation climates in most area of Japan are suitable for growing crops. However, the arable lands are limited. A small scale field experiment was conducted on a sandy soil in the Tottori sand dune to test nitrogen (N)-use efficiency from a regular N fertilizer {ammonium sulfate [(NH4)2SO4]} and a mixture of resin-coated N fertilizers for peanut (Arachis hypogaea L. cv. Hanritusei) production. Nitrogen was applied at 30, 60, 90, and 120 kg N ha−1 for the regular N, and at 60, 90, and 120 kg N ha−1 for the mixture of coated N-phosphorous (P)-potassium (K) 80 days, NPK 140 days and ammonium nitride (NH4NO3) + limestone 120 days, each providing 35, 35, and 30% of N supplied. Sufficient P and K and a micronutrient fertilizer were included. Water was applied through drip irrigation. The seed yields were 81 to 137% higher with the coated N than with the equivalent amounts of regular fertilizer N. Nitrogen recovery rates were 10% to32% for the regular N and 79–94% (average 86%) for the coated N. The high recoveries obtained with the coated N were due to the fact that N release matched crop N uptake and the fertilizer placement (beneath the seeds) allowed for immediate uptake. A highly effective N fertilization management program for crop production on this sandy soil is possible. A carbon (C):N ratio of 16.9 and 13.4 in the seeds was found with the regular N and the high rates of coated N treatments, respectively, indicating the seed quality was significantly affected by N application from the different sources.

A model of oxidation of an elemental sulfur fertilizer in soils

Elemental sulfur (S) fertilizer (S0) has to be oxidized by microorganisms to produce plant available SO4−2-S. This biological reaction is affected by many factors that influence the soil microbial population and activity and is difficult to describe mathematically. In simulating a S0 fertilizer application in the field, we discovered that by adding an exponent (n) to the incubation time (t) of the traditionally accepted first-order equation, the SO4−2-S production could be predicted. The equation that describes this relationship is St = S0 · [1-exp(-kt n)], where St is cumulative SO4−2-S produced from applied S0 at time t, S0 is S0 applied when t = 0, k is the oxidation rate constant, and n is a time function modification factor. The equation was tested in two cultivated chernozemic soils receiving fertilizer-size granule S0 (2.00–3.36 mm diameter) and fine-particle S0 (<44 μm diameter) incubated at 5, 10, and 20 °C at a moisture content of 60% of field water holding capacity. Between 88 and 99% of the variation between predicted and measured SO4−2-S (P < 0.001) was explained, and the predicted values were at a range of 99 to 102% of the measured values with limited variation (SE ≤ 4% of the mean). The modified equation offers a promising tool to predict the available S provided over time based on the amount of S0 fertilizer applied and may have the potential for use in industry and in environmental studies.

Effectiveness of hydrated lime and artificial zeolite amendments and sedum (Sedum sediforme) plant cover in controlling soil erosion from an acid soil

There are over 350 different species of sedum (Sedum spp.) and most of them can tolerate harsh conditions including very cold to hot temperatures, drought, and poor and stony soil. Sedum plants are used in rock gardens and edging flower beds, and for greening the tops of buildings, cottages, and thatched roofs. However, little is known about the effectiveness of sedum as vegetation cover in protecting soil erosion from a road embankment made of acid soil. Acid soil is believed to be vulnerable to soil erosion and is not suitable for plant growth. Liming treatment is required first before revegetation to alleviate the soil acidity; however, lime incorporation may affect the soil physical properties and, consequently, runoff and sediment generation. A rainfall simulation study was conducted to test the effectiveness of hydrated lime and artificial zeolite as amendments and Sedum sediforme (Rupestria group) as vegetation cover in controlling soil erosion from an acid soil taken from mountain cuts in Yamaguchi prefecture, Japan, where it is used for road embankment. The soil was treated with 0.5% lime and 10% zeolite. Two rainfall intensities of 30 and 60 mm/h were tested for 2 and 1 h, respectively, on sedum-growing soil plots measuring 0.50 by 0.30 by 0.05 m. Three levels of vegetation cover (bare soil, 25%, 75%) of sedum plant of 5-month growth under 2-day irrigation intervals were tested. The incorporation of hydrated lime and artificial zeolite amendments improved wet aggregate stability, which contributed to significant decrease in surface runoff, sediment concentration, and total soil loss by rain splash from the bare soil. Zeolite was more effective in promoting plant growth than the lime treatment; as a result the decrease in sediment generation and soil loss by rain splash, compared with the control, was larger with zeolite than with lime. Under both intensities of simulated rain, the sediment concentration and total soil loss by rain splash decreased significantly (P < 0.05) with increasing surface cover. The correlation between cumulative soil loss (CSL) and cumulative surface runoff was linear and significant (P < 0.001) and the slope coefficient decreased with increasing surface cover. This suggests that the sediment carrying capacity or the erosivity of the surface runoff was constant and it decreased with increasing surface cover. The sedum cover reduced the CSL up to 72 and 79% under 30 and 60 mm/h rainfall intensities, respectively. The mean weight diameter of the soil sediment transported by runoff and soil loss by rain splash were significantly increased, and therefore, the silt and clay proportion of the crust material formed on the soil surface decreased up to 6 and 16% under 25 and 75% vegetation cover, respectively. These results demonstrate that hydrated lime and artificial zeolite could be used as amendments and sedum plant as vegetation covers in controlling soil erosion from an acid soil.

Methods of pH determination in calcareous soils: use of electrolytes and suspension effect

Determination of pH assists in understanding many reactions that occur in soil. However, measured values of soil pH can be affected by the procedure used for determination and by a range of soil properties. In this study, pH was measured in different electrolytes [distilled water (pHw), 0.01 m CaCl2 (pHca), 1 m KCl (pHk), and 0.01 m BaCl2 (pHba)] with different soil : solution ratios (i.e. 1 : 1, 1 : 2.5, 1 : 5), the main objective being to study the influence of different electrolytes on the suspension effect of pH in calcareous soils. Soil pH measured in water showed significant differences between different dilution ratios and was highly influenced by the ‘suspension effect’. Other electrolytes (CaCl2, KCl, BaCl2) were little affected by the suspension effect, giving approximately stable values when pH was measured with and without stirring. High soil salinity appeared to suppress any suspension effect in a manner similar to electrolytes when added to non-saline soils.

Ameliorative Effect of K-type and Ca-Type Artificial Zeolites on the Growth of Beets in Saline and Sodic Soils

Abstract Beets were grown on soils with various exchangeable sodium percentages (ESP). A saline non-sodic soil (SA, ESP = 3.2), a saline sodic soil (SO, ESP = 23), and a saline high sodic soil (HSO, ESP = 78) were prepared from Tottori sand dune soil (CO). K-type and Ca-type artificial zeolites (50 g kg−1) were applied to these soils in order to evaluate their effects on the chemical properties of saturation extracts of the soils, water deficit, cation uptake and transport, and cation balance of beet plants. In the zeolite-free treatments, beet growth was accelerated in SA and SO, but was suppressed in HSO compared with CO. The addition of both types of zeolites ameliorated plant growth in all the soils studied, especially HSO. The relative dry weight of the soils treated by the K-type zeolite to the zeolitefree soil was 189% for CO, 125% for SA, 130% for SO, and 222% for HSO. For the soils treated with the Ca-type zeolite, the values were 169, 116, 132, and 341%, respectively. In SA, SO, and HSO, the addition of the K-type zeolite increased the K uptake due to the increase of the K concentration of saturation extracts of soils. The addition of the Ca-type zeolite increased the Ca uptake due to the increase in the Ca concentration of the saturation extracts of soils which was accompanied by an increase in the K uptake. The increase in the uptake of K or Ca and decreased in the transport of Na by the addition of both types of zeolites improved the cation balance of the plants. The Ca-type zeolite did not increase the water deficit even though it increased the electric conductivity in all the soils. The results indicated that both types of artificial zeolites were able to improve the growth performance of beets in saline and sodic soils and that the K-type zeolite could be used as a K-fertilizer as well.

Effect of Gypsum and Polyacrylamide Application on Erodibility of an Acid Kunigami Mahji Soil

Calcium carbonates and gypsum are often used to improve the chemical status of acid soils. This study discusses the effects of gypsum and polyacrylamide (PAM) application on infiltration and erodibility of a Japanese acid soil. Acid Kunigami mahji soil (sedimentary rock derived, Typic Hapludult) from Okinawa was packed into an acrylic plastic box, and simulated rainfall of 40 mm h−1 was applied. Prior to the rainfall, 2.5 t ha−1 of gypsum and/or 15 kg ha−1 of non-ionic or anionic PAM were applied onto soil surface. During a rainfall, surface runoff was collected periodically, and sediment concentration, pH, and electric conductivity of the runoff were measured. Gypsum application enhanced surface runoff. During the rainfall, EC of the runoff was greater than the critical coagulation concentration of the clays of the mahji soil, however the soil became dispersive with gypsum application. PAM application could improve infiltration of gypsum amended mahji soil and reduce sediment loss.

Control of Clogging in Microirrigation Using Wastewater in Tohaku, Japan

To identify/assess the causes of emitter clogging and its relationship with microirrigation system management using wastewater, a drip irrigation experimental system was installed in a field located in central part of agricultural zone of Tohaku, Japan. The water quality analyses shown except of pH others chemical and composition factors of irrigation water are ranked slight. The pH of irrigation water was moderate in minimum values and ranked severe during the irrigation season. Total number of planktons in irrigation water was classified moderate in maximum concentration. The main planktons genera in irrigation water were Synedra and Asterionella with 40-350 µm length, which suggestion that the planktons even in low concentration are the main factor causes of emitter clogging in Tohaku area. The uniformity indices, Vpf, Uc, and Dra have been used to evaluate performance and to rank the emitters with respect to clogging. The values of uniformity index (Uc) indicated all emitters belong to high classification (>89%). The value of Dra indicated the emitters type 1, 2 and 7 were in the mean classification for a while during the irrigation season. The values of Vpf in most of emitter type were ranked in mean classification. The uniformity indexes and emitter’s specification shown that (i) the emitters type No. 1, 2, 3, 7, and 10 are more sensitive to kind of biological clogging for Tohaku area (ii) the filtration area in emitter’s structure is an affective factor to prevention of clogging (iii) water flow cross section and working pressure are not an affective factor to prevention of clogging in emitters solely.

Using digital photogrammetry to monitor soil erosion under conditions of simulated rainfall and wind

We investigated a method to measure sheet erosion by characterising the soil erosion of an upland field in a dryland environment. Digital photogrammetry was used to measure the erosion rates of soil surfaces packed to different densities under simulated rainfall or wind conditions. The photogrammetry system consisted of 2 digital cameras, a rainfall simulator, a wind tunnel, and a computer program for 3-dimensional algorithm analysis. First, we assessed the accuracy of our method by comparing conventionally measured data to photogrammetric data under conditions of either no rainfall or no wind application. Two statistical parameters were used to evaluate the soil surface evolution: the mean absolute error (MAE) and the mean relative error (MRE). Their values were 0.21 mm and 15.8%, respectively. We then assessed the precision of our system under simulated rainfall conditions using 3 different dry bulk densities for the packed saturated soil surface. At densities of 0.91, 0.98, and 1.09 g/cm3, the MAE (MRE) values were 2.21 mm (392.5%), 1.07 mm (126.4%), and 0.59 mm (57.6%), respectively. It was possible to monitor and evaluate both the amount of eroded soil and the erosion mechanism in a specific area. Moreover, this system could be applied to measuring wind erosion with an MAE accuracy as high as 0.21 mm. The digital elevation models (DEMs) allowed for detailed analyses of soil surface evolution, and it was also possible to monitor sheet erosion with high spatial and temporal resolutions.