Epsilon Archive for Student Projects

Abstract

Green manuring is a way of creating an organic fertilizer by growing a crop that is mowed down. Besides the fertilizing effect this method has been shown to have a positive influ-ence on soil organic matter as well as weed flora, and green manure is an important me-thod of weed control in organic farming in parts of Sweden. However, the release of nu-trients from the green manure varies and can therefore be difficult to control. Risks for losses of nutrients are also present. Although the area of organic farmland is increasing in Sweden, the use of green manure is decreasing.

This report contains a literature study which compiles research on the functions of green manure in a cropping system and also how the crop can be used if harvested, for example to produce biogas. The second part of the report is based on interviews with a number of farmers using green manure. The interviews were made as semi-structured conversations and the method was qualitative. The main objective has been to investigate the farmers’ view on green manure and the reasons for them to use it. The advantage of green manure according to the interviewees is the supply of several services such as weed control, in-creased biodiversity and an improvement in soil structure. Some mention the disadvantage of the lost opportunity of growing a cash crop, but the greater part of those interviewed believe that including green manure in a crop sequence is a sustainable way of farming.

A comparison is made between two regions in Sweden, Eastern Gothia and the region of Mälaren, which both have a lot of crop production without cattle management. In the re-gion of Mälaren the use of green manure is frequent on organic farms with crop produc-tion. In Eastern Gothia the situation is the opposite: the method is used only on very few farms. In both regions the replacement of green manure with ley for seeds or fodder is in-creasing. The potential of marketing of the harvested ley is higher in Eastern Gothia where the access to alternative organic fertilizers is also better. In the same region the multi ma-chine System Cameleon is used, which enables new crop sequences within organic farm-ing, where weed control is performed by harrowing.

The use of green manure crops may henceforth play an important role in organic agri-culture as weed control and soil amendment. The fertilizing effect however seems to have lost importance with the rise of alternative fertilizers on the market. Methods of recircula-tion of nutrients and local production of fertilizers should be developed as future alternatives.