Residual effects of subsoil zinc and oilseed rape genotype on the grain yield and distribution of zinc in wheat

Abstract

The residual effects of Zn supplied (+Zn: 1 mg kg−1 soil, -Zn: no Zn added) in subsoil to four oilseed rape genotypes (Zhongyou 821, Xinza 2 and Narendra: Brassica napus type, and CSIRO-1: Brassica juncea type) were studied on the following wheat in a glasshouse experiment in pots (100 cm long, 10.5 cm diameter). The topsoil (upper 20 cm soil in pots) was supplied with Zn (0.5 mg kg−1 soil) in all treatments whereas Zn (1 mg Zn kg−1 dry soil) was either supplied or omitted from the subsoil at time of sowing of oilseed rape genotypes. Oilseed rape plants were harvested at maturity and wheat (variety Songlen) was grown to evaluate the residual effects of subsoil Zn and oilseed rape genotypes. Subsoil residual Zn significantly improved the root growth, yield attributes, grain and straw yield of wheat. Wheat grain Zn concentration was 4 times higher in +Zn subsoil residual than under -Zn subsoil residual. Oilseed rape genotypes did not vary in their residual effect on grain and straw yield of wheat, but reflected a differential effect on Zn concentration and Zn content of wheat grain. Zinc uptake per wheat plant (grain + shoot + root Zn uptake) was about 4 times higher in +Zn subsoil residual than -Zn subsoil residual. Out of total Zn uptake per plant, 77%, 15% and 8% of Zn was loaded in wheat grains, shoots and roots respectively in +Zn subsoil residual. However in -Zn subsoil residual, distribution of Zn in grains, shoots and roots was 55%, 29% and 16% respectively. Zinc loading in grains of wheat was significantly higher in wheat grown after Narendra and Xinza 2 compared with wheat grown after Zhongyou 821 (Zn-inefficient genotype). These results indicate that subsoil residual Zn and Zn-efficient genotypes of oilseed rape have the potential to increase the Zn loading in wheat grains.