Green Manuring: Principles and Practice

Abstract

THE growing inadequacy in the supplies of farmyard manure throughout the world has put a premium on the importance of green manuring, and much attention is being paid to the most profitable utilisation of this method of soil improvement. The actual practice is of very ancient date, but scientific interest in what really goes on in the soil when green crops are ploughed under has only been aroused comparatively recently. Dr. Pieters attacks his problem both from the theoretical and practical points of view, keeping the economic factor well before him. The effects of organic matter in the soil are both physical and biochemical, and the action of the soil micro-organisms encouraged by its presence may react favourably or unfavourably to crop plants according to circumstances. The turning under of much green material low in nitrogen may result in reduced crop yields, owing to the utilisation of the soil nitrates by micro-organisms, whereas leguminous or other material high in nitrogen benefits crops, owing to the release of ammonia which is converted into nitrates. As yet our knowledge of what actually happens in the soil is far from complete, resulting in frequent failures when green manuring is attempted under faulty conditions. Much more research is needed to enable cultivators to make the fullest and best use of this extremely valuable source of organic matter in the soil.

Green Manuring: Principles and Practice.

By Dr. Adrian J. Pieters. (The Wiley Agricultural Series.) Pp. xiv + 356. (New York: John Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1927.) 22s. 6d. net.