Enhance Soil Quality and Cowpea Productivity using Different Types of Soil Improvement Materials includes compost, Biochar, and potassium feldspar under Sandy Soil Conditions

Abstract

Purpose: Cowpea (Vigna unguiculata) is a vital legume crop in Egyptian agriculture, contributing to food security and soil fertility enhancement. Egypt is forced to import potassium fertilizers due to the lack of natural raw materials needed to manufacture K fertilizers, which is necessary to improve the quality of grain crops and helps with stand abiotic and biotic stresses. The present study investigates effects of three different soil improvement materials includes compost (Comp), Biochar (Bioch), and potassium feldspar (KFd) on cowpea productivity and enhances sandy soil quality properties. Methods: A field experiment was conducted over two summer growing seasons of 2020 and 2021 at Isma3elia agricultural research station farm using cowpea cultivar Dokki 126 in a randomized complete block (RCB) statistical design. Eight treatments were tested, including control, individual amendments, and combined applications of KFd, Bioch and Comp, Soil physical and chemical properties, plant growth parameters, and NPK nutrient content were determined. Results: The combined trio application of Comp, Bioch and KFd significantly improved soil structure by reducing bulk density (from 1.62 g/cm³ in control to 1.28 g/cm³) and increased total porosity (from 47.5% to 39.3%). Soil organic matter content (SOMC) was the highest in the trio combined treatment (0.71%) compared to control (0.50%). Additionally, mineral nitrogen (MN) 49.10 mg kg-1), available phosphorus (AP) (6.62 mg kg-1), and exchangeable potassium (EK) (187 mg kg-1) were maximized under the same treatment. Cowpea plant growth parameters showed remarkable improvement, with extra growth reaching 305 cm in height compared to 144.3 cm in the control. Pod characteristics, including pod length (24.23 cm vs. 17.45 cm in control) and fresh weight (12.33 g vs. 7.29 g), were also significantly enhanced. Photosynthetic pigments and carbohydrate content in seeds increased, further supporting higher productivity. Conclusion: The combination of Comp, Bioch and KFd proved to be the most effective soil
improvement combination, enhancing soil fertility, plant growth, and cowpea yield. These findings suggest that integrating organic and primary materials as soil amendments can improve productivity while reducing dependency on synthetic fertilizers in Egyptian agriculture.