A nitrogen fixing microbe associated with Azolla in rice fields is
1. Spirulina
2. Anabaena
3. Frankia
4. Tolypothrix

Nitrifying bacteria
1. convert free nitrogen to nitrogen compounds
2. convert proteins into ammonia
3. reduce nitrates to free nitrogen
4. oxidize ammonia to nitrates

An organism used as a biofertilizer for raising soyabean crop is
1. Azospirillum
2. Rhizobium
3. Nostoc
4. Azotobacter

An element playing important role in nitrogen fixation is
1. molybdenum
2. copper
3. manganese
4. zinc

Which one of the following is not a micronutrient?
1. Molybdenum
2. Magnesium
3. Zinc
4. Boron

The free-living, anaerobic nitrogen-fixer is
1. Beijerinckia
2. Rhodospirillum
3. Rhizobium
4. Azotobacter

A plant requires magnesium for

Farmers in a particular region were concerned that pre-mature yellowing of leaves of a pulse crop might cause decrease in the yield. Which treatment could be most beneficial to obtain maximum seed yield?
1. Frequent irrigation of the crop
2. Treatment of the plants with cytokinins along with a small dose of nitrogenous fertilizer
3. Removal of all yellow leaves and spraying the remaining green leaves with 2, 4, 5 trichlorophenoxy acetic acid
4. Application of iron and magnesium to promote synthesis of chlorophyll

Sulphur is an important nutrient for optimum growth and productivity in:
1. pulse crops
2. cereals
3. fibre crops
4. oilseed crops

If by radiation, all nitrogenase enzymes are inactivated, then there will be no
1. Fixation of atmospheric nitrogen
2. Conversion from nitrate to nitrite in legumes
3. Conversion from ammonium to nitrate in soil
4. Fixation of nitrogen in legumes