Optimum Olsen Phosphorus/Zinc DTPA ratio for the initial growth of maize in agricultural soils of the Mediterranean region.

Background: Zinc (Zn) deficiency in crops is commonly aggravated by high levels of phosphorus (P) in soil. In this work, the initial performance of pot-growing maize in response to the available P and Zn in soils with low available Zn and to the application of P and Zn fertilizers was investigated.
Results: The soils (six non-calcareous and 14 calcareous) ranged widely in available P (Olsen P: 5.5-37.9 mg kg ^-1 ), were poor in available Zn [diethylenetriaminepentaacetic acid-extractable Zn (Zn _DTPA ): 0.20-0.84 mg kg ^-1 ] and had an Olsen P/Zn _DTPA ratio of 13 to 111 mg mg ^-1 . Soil P application generally increased aerial dry matter (ADM) yield; Zn increased ADM yield mostly when applied in combination with P; and the sole application of Zn increased yield only in a soil with a high (28 mg kg ^-1 ) Olsen P and a low (0.36 mg kg ^-1 ) Zn _DTPA . The increase in ADM yield resulting from optimal application of P and/or Zn to the soil was modest in soils where the Olsen P/Zn _DTPA ratio was 30-60 and Olsen P was >14 mg kg ^-1 . Zinc uptake by the control plants was correlated with the Zn _DTPA of the soil. For a certain Zn _DTPA value, the level of plant available Zn was higher in non-calcareous than in calcareous soils.
Conclusion: Soil application of fertilizer P and Zn, in soils with low levels of available Zn, should not only aim at increasing the available P and Zn levels but also balancing them at the appropriate Olsen P/Zn _DTPA ratio, which was found to lie in the 30-60 range in the present study. © 2020 Society of Chemical Industry.
(© 2020 Society of Chemical Industry.)