Anew optimum value for zinc in the main maize producing sandy soils of South Africa

Abstract

South African farmers commenced applying zinc (Zn) during the 1960s at a rate of approximately 2 kg Zn ha⁻¹. Although good yields were produced and Zn levels increased in South African maize fields, a recent survey revealed that maize meal contained subnormal levels of Zn, and therefore needed to be fortified with Zn for human consumption. An existing, valid, historic dataset was revisited to throw light on this subject that has lately become topical. Those experiments were conducted during 1997–2001 at seven localities in the main maize producing area of South Africa to establish a new optimum value for Zn in maize producing sandy soils. Treatments included a reference when all nutrients were applied and another when zinc was omitted. A Zn optimum value of 3.8 mg Zn kg⁻¹ in the topsoil, extracted with 0.1 M HCI-solution was established as obtained with linear-linear and quadratic regression methods.

Keywords:

• Threshold value
• critical value
• soil extraction
• maize
• zinc