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

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 Nare ndra: 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 oils eed rape genotypes. Oilseed rape plants were harvested at maturity and whea t (variety Songlen) was grown to evaluate the residual effects of subsoil Z n and oilseed rape genotypes. Subsoil residual Zn significantly improved th e root growth, yield attributes, grain and straw yield of wheat. Wheat grai n Zn concentration was 4 times higher in +Zn subsoil residual than under -Z n subsoil residual. Oilseed rape genotypes did not vary in their residual e ffect on grain and straw yield of wheat, but reflected a differential effec t 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 subs oil residual than -Zn subsoil residual. Out of total Zn uptake per plant, 7 7%, 15% and 8% of Zn was loaded in wheat grains, shoots and roots respectiv ely in +Zn subsoil residual. However in -Zn subsoil residual, distribution of Zn in grains, shoots and roots was 55%, 29% and 16% respectively. Zinc l oading in grains of wheat was significantly higher in wheat grown after Nar endra and Xinza 2 compared with wheat grown after Zhongyou 821 (Zn-ineffici ent genotype). These results indicate that subsoil residual Zn and Zn-effic ient genotypes of oilseed rape have the potential to increase the Zn loadin g in wheat grains.