Which nutrient is helpful in Nitrogen fixation in roots of pulse crops?

Which of the following is macronutrient in relation to growth of plants?

Which of the following nutrient is necessary for 'Nodule Formation' in legumes?

Which of the following nutrient is most useful for enhancing oil content in mustard crop?

Which of the following elements is NOT a micronutrient in plants?

Nitrogen-fixing bacteria establish symbiotic combinations with the cells of the roots of which plants?