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Total Potassium Concentration of Major Paddy Growing Soils in Sri Lanka

Fri, 01 Jan 2021 00:00:00 GMT

Title: Total Potassium Concentration of Major Paddy Growing Soils in Sri Lanka Authors: Madushan, N.D.R.; Neththasinghe, N.A.S.A.; Ekanayake, E.M.S.; Rathnayake, W.M.U.K.; Sirisena, D.N.; Dissanayaka, D.M.S.B.; Ariyaratne, M.; Suriyagoda, L.D.B. Abstract: Total potassium (K) concentration represents the K pool in a soil, and that provides the required K for plant uptake after making K available through biochemical changes. Knowledge on K pool in different soil types is important for sustainable management of crops and soils. Therefore, this research was conducted to estimate the total K concentration in different rice growing soil types from agro-climatic zones (ACZs) of Sri Lanka. Total of 200 soil samples representing six ACZs (except for Upcountry Wet zone) in Sri Lanka were collected though a stratified random sampling approach. Soil total K concentration was determined through X-ray florescence (XRF) analyser. Soil total K concentration had a wide range of values i.e. 316-31,153 mg kg−1. The Reddish Brown Earths & Immature Brown Loams (RBE IBL) had the highest soil total K concentration (20,127 mg kg−1) followed by Rock Knob Plain (RKP), Reddish Brown Earths with high amount of gravel in subsoil & Low Humic Gley (RBE-LHG), Noncalcic Brown soils & Low Humic Gley soils (NB LHG), Reddish Brown Earths, Noncalcic Brown soils & Low Humic Gley (RBE-NB LHG) and Noncalcic Brown soils, soils on old alluvium & Solonetz (NB-S) soils. All these soils had total K concentration greater than 13,000 mg kg-1. Soils of Bog and Half-Bog soils (BHB) and Red-Yellow Podzolic soils with soft or hard laterite (RYP) reported the lowest total K, i.e. <5,000 mg kg-1. Soil total K concentration was high in Intermediate Zone Upcountry followed by Dry Zone Low Country, Intermediate Zone Low Country and Intermediate Zone Mid Country and the lowest in Wet Zone Low Country. The results confirm that, soil total K concentration in Sri Lankan paddy growing soils had a clear spatial variability associated with soil type and ACZ. This information would be important for sustainable K-nutrient management in Sri Lankan rice fields.

Total and Available Phosphorus Concentrations in Major Rice Growing Soils and Their Relationships with Rice Grain Phosphorus Concentration

Fri, 01 Jan 2021 00:00:00 GMT

Title: Total and Available Phosphorus Concentrations in Major Rice Growing Soils and Their Relationships with Rice Grain Phosphorus Concentration Authors: Neththasinghe, N.A.S.A.; Madushan, N.D.R.; Ekanayake, E.M.S.; Rathnayake, W.M.U.K.; Sirisena, D.N.; Suriyagoda, L.D.B. Abstract: Phosphorus (P) is an essential macro nutrient for plant growth and development. Soil P exists in organic and inorganic forms. However, only a fraction of soil P is readily available to plant. Plant available and total P concentrations in soils vary among soil types due to the differences in soil mineralogy, structure, physical & chemical properties, and fertilizer application. Therefore, this research was conducted to estimate the concentrations of plant available and total P in major rice growing soils (i.e. 18 soil types) in Sri Lanka, and to study their relationships with grain P concentration. Total of 200 soil samples and grain samples were collected representing paddy lands across the country using a stratified random sampling approach. Available P (Olsen-P) and total P in soils, and grain P concentrations were measured. Available P concentration in paddy soil samples ranged from 5.4-76.9 mg kg−1. The highest available P concentration was recorded in Reddish Brown Earths & Immature Brown Loams soil (RBE_IBL) (34 mg kg−1) and the lowest in Red-Yellow Latosols soil (RYL) (12 mg kg−1). Soil total P concentration had a wide range of values i.e., 142-5685 mg kg−1. The Red-Yellow Podzolic soils with soft or hard laterite (RYP) had the highest soil total P concentration (2525 mg kg−1). Grumusol soil and RYL soil reported the lowest total P, i.e., < 1000 mg kg-1. Grain P concentration varied among soil types and it ranged between 0.6-1.8 mg g-1. However, there was no correlation between the grain and soil P concentrations. This information would be important for sustainable P-nutrient management in Sri Lankan rice soils.

Relationships between Total Mineral Element Concentrations of Major Paddy Growing Soils in Sri Lanka

Fri, 01 Jan 2021 00:00:00 GMT

Title: Relationships between Total Mineral Element Concentrations of Major Paddy Growing Soils in Sri Lanka Authors: Madushan, N.D.R.; Ekanayake, E.M.S.; Neththasinghe, N.A.S.A.; Samarasinghe, D.A.T.; Rathnayake, W.M.U.K.; Sirisena, D.N.; Suriyagoda, L.D.B. Abstract: The knowledge on the accumulation of essential and toxic trace elements in rice growing soils is crucial for sustainable soil nutrient management and rice crop production. The aim of the present study was to investigate the total concentration of essential and toxic trace elements and their relationships in Sri Lankan paddy soils. Two hundred soil samples were collected representing three climatic zones and seventeen soil types using stratified random sampling approach. The total elements concentrations were measured using X-ray florescence (XRF) analyzer. The minimum and maximum total element concentrations were determined using descriptive statistics. Relationships among total element concentrations were tested using correlation and principle component (PC) analyses, and the concentrations of elements among climatic zones and soil types were compared using ANOVA. The highest mean total element concentration in soil samples was recoded in Fe which ranged from 220 to 71,994 mg kg-1 followed by K (316-31, 153 mg kg-1) and Ca (44-19, 436 mg kg-1). The lowest mean total concentrations were observed in As and Mo (<3 mg kg-1). Soil Fe concentration was positively correlated with Mn, Cu, Zn, As and Pb (r > 0.5, p<0.05). Among the climatic zones, Wet Zone soils (WZ) contained higher concentrations of Fe, Zn, As and Pb whereas Dry Zone and Intermediate Zone soils had higher concentrations of Ca and K compared to WZ soils. When compare different soils categories, Bog and Half-Bog soils and Red Yellow Podzolic soils had higher Fe, Zn, As and Pb concentrations whereas lower concentration of Ca and K were observed. The highest Mn concentration was in Grumusols while Cu concentration was relatively uniform in all soil types tested. Elements concentrations and their relationships studied in this research would be important in sustainable nutrient management in Sri Lankan rice fields.

Quality Rice Flour Production for Extruded Products through Wet-Milling

Fri, 01 Jan 2021 00:00:00 GMT

Title: Quality Rice Flour Production for Extruded Products through Wet-Milling Authors: Farwin, M.H.I.; Prabhaharan, M. Abstract: Rice (Oryza sativa L.) is one of the leading cereal crops in the developing world. Rice grain is a major source of carbohydrates, protein and other essential nutrients. The Degree of Milling (DOM) is a term used to describe the milling process. With an increase in DOM, the preservation of bran decreases. This, in turn, has an influence on the level of head rice yield and the related economics. Sri Lanka has two types of raw rice varieties based on pericarp color. Those were white rice and red rice which contained polished red rice and unpolished red rice. This study was aimed to investigate the quality of extruder processed rice flour from raw rice at different intervals of soaking as it is a significant factor in determining the quality of rice products. The weight of 100 grains, length, width and whiteness value of raw rice samples were tested. Rice grinding has been used to minimize particle size and to obtain rice flour. Rice flour yield of white rice, polished rice and unpolished rice with 256 microns sieved were 96%, 92% and 90% respectively. Based on this outcome of extruded products, it can be concluded that soaking for two hours is needed for white rice and polished rice to get optimum yield through wet-milling and unpolished red rice requires 4 hours of soaking to give optimum yield. The quality of the flour products depends on the soaking time and the type of milling. All the raw rice can be used for the wet-milling after 2 to 4 hours of cold water soaking to yield more than 90% of 256-micron particle size granules.