Readings

• US Geological Survey. Fertilizers – Sustaining Global Food Supplies. 1999. University of Massachusetts Amherst. Fertilizers.

Key Questions

Fertilizers – Sustaining Global Food Supplies

• Which crops among the major crops of the US have high fertilizer recommendation?
• Why is fertilizer application more than recommended in most crops – corn, cotton and rice?
• Why is nitrogen application lower than recommended in soybean?
• What are the reasons for increasing sulfur deficiency in the soils of the world?
• How self sufficient is the US pertaining to the major nutrient ( N,P,K,S) requirements?
• What are the issues that may lead to variations in fertilizer production and use in the US?
• What are the environmental risks posed by fertilizer manufacture and use?
• Which nutrient is a major contributor to eutrophication of lakes? What are the options available to manage this phenomenon?

Fertilizers

• What is the distinction between high and low grade fertilizers?
• What does it mean when the fertilizer grade on the bag reads 10:10:10?
• What are the roles of N, P and K in crop production?
• What is nitrogen fixation?
• What are the problems from over-fertilizing with N?
• Why does overfertilization with nitrogen result in the crop being more susceptible to pests?
• What are the major differences between organic and chemical sources of nitrogen fertilizers?
• What special considerations would a farmer take while using organic nitrogenous fertilizers?
• Which forms of nitrogenous fertilizers are most commonly and widely used in US agriculture?
• What are some of the important points to be considered while applying urea on crops?
• Why should safety precautions be taken while using ammonium nitrate?
• Would you recommend ammonium sulfate on an acidic soil?
• Would you recommend ammonium sulfate on sulfur deficient soils?
• What is the disadvantage of calcium nitrate, despite it being a high quality nitrogenous fertilizer?
• How is nitrogen mineralization different in blood and seed meals? Does this affect the time of application for crop production?
• Can sewage sludge application on food crops pose a risk?
• What is phosphorous fixation? How can this be reduced?
• Does P pose a risk of leaching?
• Which other nutrients do superphosphate fertilizers supply?
• Despite occurring naturally, why is potassium chloride not accepted in organic farming?
• What precaution would be necessary if one were to use plant materials as a source of potash?