Dry matter production and uptake of zinc and phosphorus in two oilseed rape genotypes under differential rates of zinc and phosphorus supply

The effects of varied supply of zinc (Zn) (0, 0.1, 0.2, 1.0, and 10 mg Zn kg⁻¹ soil) and phosphorus (P) (low P: 50 mg P kg⁻¹ soil and high P: 150 mg P kg⁻¹ soil) on vegetative growth, plant tissue Zn and P concentration and their uptake were studied in six weeks old plants of two oilseed rape (Brassica napus) genotypes (92–13, a traditional genotype from China high in both erucic acid and glucosinolate, and Xinza‐2, a hybrid from China low in erucic acid and glucosinolate) grown in Laffer sand (low in Zn and P) under controlled environmental conditions. Two oilseed rape genotypes had a differential response to Zn application. Xinxa 2 responded significantly for shoot and root dry matter only up to 0.1 mg applied Zn kg⁻¹ soil, while 92–13 responded up to 0.2 mg Zn kg⁻¹ soil. Zinc at 10 mg kg⁻¹ soil slightly reduced shoot dry matter and drastically reduced root dry matter of both the genotypes. Shoot and root dry matter production at 0, 0.1, 0.2, and 1 mg Zn kg⁻¹ soil were significantly greater under high P supply compared with low P supply. High P supply did not accentuate Zn deficiency symptoms compared with low P supply even at nil Zn. Phosphorus concentration in plant parts was significantly higher at nil Zn compared with Zn application. An increase in P supply had a non‐significant effect on Zn concentration, but significantly increased the P concentration and P uptake in shoots. The results suggest that an increased supply of P at lower rates of Zn application was not detrimental for early vegetative growth and Zn uptake of two oilseed rape genotypes.Zhonggui Lu, Harsharn Singh Grewal & Robin D. Graha