Các chất dinh dưỡng thực vật có thể được chia thành các chất dinh dưỡng lớn và nhỏ hoặc vi chất dinh dưỡng. Ba trong số các chất dinh dưỡng lớn, nitơ (N), phốt pho (P) và kali (K), là quan trọng nhất và được sử dụng ở mức độ lớn nhất. Ba chất dinh dưỡng thực vật này là những thành phần được liệt kê về phân bón bán tại các cửa hàng. Canxi (Ca), magiê (Mg), và lưu huỳnh (S) cũng là những chất dinh dưỡng quan trọng kể từ khi nhà máy sử dụng đến một mức. | CHAPTER 3 Plant Nutrients INTRODUCTION Plant nutrients can be subdivided into major nutrients and minor or micronutrients. Three of the major nutrients nitrogen N phosphorus P and potassium K are the most important and are utilized to the greatest extent. These three plant nutrients are the ingredients listed on fertilizers sold at stores. Calcium Ca magnesium Mg and sulfur S are also major nutrients since the plant utilizes them to a greater extent than minor or micronutrients. The micronutrients essential to plant growth are boron B copper Cu iron Fe manganese Mn molybdenum Mo nickel Ni and zinc Zn . It has been recognized for centuries that sewage sludge and biosolids contain plant nutrients. Noer 1926 cited Bruttini 1923 who estimated that the annual excrement of the world s population contains approximately 9 million tons of nitrogen N and close to a million tons of phosphoric acid P2O5 and potash K2O that are lost to agriculture. Based on this data Noer 1926 estimated that the annual loss to the United States is approximately million tons of N valued at 180 million and more than 100 000 tons each of P2O5 valued at 12 million and K2O valued at 10 million. Today this number would be much higher. It is estimated that the . produces approximately 2 million dry tons of sludge and biosolids. This approximates to 10 million wet tons. Assuming an average of 4 nitrogen the N in sewage sludge and biosolids would amount to about 400 000 tons that could be available to crops. Approximately 250 000 tons of P would be available to crops. In addition significant quantities of minor elements Ca Mg and S would be available. In many cases soils in the United States are deficient in these nutrients and farmers must add them at significant cost. In 1977 Sommers obtained data on the nutrient content in 250 sewage sludge samples from 150 wastewater treatment plants. The data on the major plant nutrients including calcium Ca magnesium Mg and sulfur S are presented in Table .
