Soil Characterization, Investigating Phosphorus Sorption Capacity and Response of Crops to Liming and Phosphorus on Acid Soils of Bako Tibe and Omo Nada Districts of Oromia Region, Ethiopia

No Thumbnail Available

Date

2024-06

Journal Title

Journal ISSN

Volume Title

Publisher

Addis Ababa University

Abstract

Soil characterization is essential for understanding the properties, causes, and effects of acidic soils and devising appropriate management options. Soil acidity and phosphorus fixation are major causes of soil fertility decline and crop yield reduction in Ethiopian highlands. The high P-fixing property of soils makes available P below crop demand. A study was conducted to characterize and classify agriculturally potential acid soils, assess phosphorus sorption capacity, determine the external P and lime requirement of different soils, and evaluate the response of wheat to phosphorus application rates in the study area. Four soil types were considered, and twelve representative Pedons were opened and described. A total of 97 (52 disturbed and 45 core ring, undisturbed) soil samples were collected from identified horizons and examined in the field and laboratory for soil characterization. The soils were categorized into different reference soil groups (RSG). Phosphorus-sorption data were obtained by equilibrating 1 g of the 12 soil samples with 25 ml of KH2PO4 in 0.01 M CaCl2, having 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, and 330 mg P L-1 for 24 hours. The relationship between phosphorus sorption and soil characteristics was established by correlation analysis. The magnitude of the soil's phosphorus sorption capacity and external P requirement were affected by clay content, exchangeable acidity, organic matter, Al2O3, and Fe2O3. Alisols had the highest Kf value (413 mg P kg-1), followed by Luvisols (336 mg P kg-1), Andosols (280 mg P kg-1), and Nitisols (280 mg P kg-1). Nitisols, Luvisols, Alisols, and Andosols, had an external phosphorus requirement of 25, 30, 32, and 26 mg P kg-1 soil sequentially. After assessing the degree of acidity of the soils, 2.28 t ha-1, 3.60 t ha-1, and 4.22 t ha-1 lime was determined (based on the exchangeable acidity method) for Nitisols, Luvisols, and Alisols respectively. The integrated effects of lime and P fertilizer on maize yield parameters and selected soil chemical properties were examined on Nitisols, Luvisols, and Alisols for two years (2017/18-2018/19) under field conditions. The experiment consisted of eight treatments: (T1) control, (T2) 50% RL + 30 kg P ha-1 + 92 kg N ha-1, (T3) 100% RL +30 kg P ha-1 + 92 kg N ha-1, (T4) twice RL + 30 kg P ha-1 + 92 kg N ha-1, (T5) 50% RL + 15 kg P ha-1 + 92 kg N ha-1, (T6) 100% RL alone, (T7) farmers Practice (200 kg NPSB +92 kg N ha-1), and (T8) 30 kg P ha-1 + 92 kg N ha-1. Soil analysis results after harvesting showed that the addition of lime increased the soil pH and exchangeable Ca2+ but decreased the levels of soil exchangeable acidity for all soil types. The Olsen available P content of plots treated with recommended lime plus critical P rate increased from 6.69 to 15.42 mg kg-1 in Nitisols, 6.71 to 22.27 mg kg-1 in Luvisols, and 5.27 to 40.92 mg kg-1 in Alisols. The application of recommended lime + critical P rates increased maize grain yield by 89.88%, 81.49%, and 84.38% over the control treatments and by 28.35%, 26.53%, and 26.73% over farmers' practices for Nitisols, Luvisols, and Alisols, respectively. Therefore, the use of twice the critical P level (60 kg P ha-1) alone or the use of critical P level combined with the recommended lime rates by soil types can be used for optimum maize production in the study area. The study also found that the use of 40 kg P ha-1 which produced the maximum wheat grain yield of all treatments can be recommended for wheat production.

Description

Keywords

Lime Rates, Pedon, Phosphorus Fixation, Soil Characterization, Yield Parameters

Citation