Relative importance 418 Scottish soils supplied with potash 419 Sources of potassic manures 419 Stassfurt potash salts 420 Relative merits of sulphate and muriate of potash 421 Application of potash manures 422 Soils and crops suited for potash manures 423 Rate of application 423 CHAPTER XVI.--MINOR ARTIFICIAL MANURES. Scutch 427 Shoddy and wool-waste 427 Soot 428 CHAPTER XVII.--SEWAGE AS A MANURE. Irrigation 431 Effects of continued application of sewage 433 Intermittent irrigation 434 Crops suited for sewage 434 Treatment of sewage by precipitation, &c. 436 Value of sewage sludge 439 CHAPTER XVIII.--LIQUID MANURE 442 CHAPTER XIX.--COMPOSTS. Farmyard manure a typical compost 446 Other composts 447 CHAPTER XX.--INDIRECT MANURES. Lime 449 Antiquity of lime as a manure 449 Action of lime 449 Lime a necessary plant-food 450 Lime of abundant occurrence 452 Lime returned to the soil in ordinary agricultural practice 452 Different forms of lime 453 Caustic lime 453 Lime acts both mechanically and chemically 455 I. Mechanical functions of lime 455 Action on soil's texture 455 Lime renders light soils more cohesive 457 II. Chemical action of lime 457 III. Biological action of lime 459 Action of lime on nitrogenous organic matter 460 Recapitulation 461