Improved Alfalfa Phosphate Utilization Using Zeolite Amendments in Low pH Soil

Abstract

Soil amendments are used to increase the solubility of phosphate rocks (PRs) such that they can supply phosphorus (P) to high P-demanding crops. Zeolites are naturally occurring aluminosilicate minerals that can solubilize PRs and increase P nutrient supply. This study sought to evaluate the effects of zeolite addition in PR mixtures in dry matter yield (DMY), nutrient accumulation, and alfalfa’s agronomic efficiency. The experiment was conducted in a greenhouse where treatments comprised of two zeolites types (clinoptilolite and stilbite), three P sources (triple superphosphate-TSP, Morocco PR, and Cajati PR), five P levels (0, 22, 44, 87, and 131 mg kg−1), and five zeolites ratios (w/w) based on P2O5 levels (0, 25, 50, 100, and 200%). Eleven cuts of alfalfa were taken to quantify DMY and P accumulation. Alfalfa dry matter yield and P accumulation increased due to P fertilization. Reactive PR (Morocco) was more effective than TSP to increase alfalfa DMY and P accumulation. Phosphorus levels in soil did not increase with reactive PR (Morocco) fertilization and zeolite amendment. Zeolite stilbite just increased P solubilization and accumulation by alfalfa plants in a 150–200% ratio (zeolite/PR) with the low-reactive PR (Cajati). Under this experiment’s conditions, zeolite was not an efficient amendment combined with P soluble and reactive PR sources to increase alfalfa DM yield and P accumulation. Large amounts of zeolite were necessary to provide the low-efficiency PR source solubilization to satiate alfalfa P demand.