tailieunhanh - ORGANIC SOILS and PEAT MATERIALS for SUSTAINABLE AGRICULTURE - CHAPTER 6

Chỉ số cân bằng nitơ và phốt pho trong đất hữu cơ Tổn thất chất dinh dưỡng từ agroecosystems phụ thuộc vào số lượng thực hành nước thải, loại đất, và quản lý. Chương này trình bày các chỉ tiêu N và P của chất lượng đất hữu cơ | CHAPTER 6 Nitrogen and Phosphorus Balance Indicators in Organic Soils Léon E. Parent and Lotfi Khiari CONTENTS Abstract I. Introduction II. Environmental Risk of Cultivating Organic Soils III. Fertilizer Trials Conducted in Quebec IV. Simplified N and P Cycles V. Nitrogen Indicators A. Nitrogen Content and Fractions B. Environmental Conditions for N Mineralization C. Management Practices to Reduce Loads of Nitrate and Nitrous Oxide in Organic Soils VI. Phosphorus Indicators A. Phosphorus Content and Fractions B. Environmental Conditions for Release of Organic P C. Environmental Conditions for Release of Inorganic P D. Good Management Practices to Reduce P Load VII. Related C N and P Cycles VIII. Need for N and P Indicators IX. Conclusion Acknowledgments References 2003 by CRC Press LLC ABSTRACT Nutrient losses from agroecosystems depend on the amount of water discharge soil type and management practices. This chapter presents N and P indicators of organic soil quality as related to water quality and crop fertilization. Organic soils contain 5 to 27 Mg organic N ha-1 in the arable layer which could release 800 to 1500 kg NO3-N ha-1 a-1 depending primarily on C N ratio and pH. Because 12 to 245 kg NO3-N ha-1 a-1 could be discharged and because crop removal cannot account for residual N most of the N must be denitrified. Organic soils contain in average 700 to 1100 mg P kg-1 of which 67 to 78 is reported to be organic P inorganic P being more or less chemically sorbed. One to 88 kg P ha-1 would be discharged annually indicating high potential risk for eutrophication. Due to the predominance of organic forms N and P microbial turnovers should be diagnosed possibly using N and P ratios or multiratios . C N N P C N P C N P S . An inorganic P sorption or saturation index as well as N and P turnover attributes as multiratios should be developed for planning N and P fertilization programs. I. INTRODUCTION Soil quality indicators can assist managers of agroecosystems in .