Green manure and inorganic fertiliser as management strategies for witchweed and upland rice

Weed infestation, especially the Witchweed (Striga asiatica) is a serious problem in fertility-depleted soils of Tanzania. The use of urea fertiliser is known to control weed but resource-poor farmers cannot afford thistechnology due to high costs involved. To alleviate the problem of Striga and soil fertility, green-manure applications could be an alternative strategy. Ths study was conducted to (a) evaluate the potential of green manure against Striga, and (b) determine the potential of inducing Striga suicidal germination by selected green manures. For the first part of the study, treatments included three green manure species, Crotolaria ochlroleuca G. (sunhemp), Mimosa invisa L.(Colla) and Cassia obtusifolia L.(Sicklepod) superimposed with three fertiliserrates 0, 25 and 50 kg N ha-1. The treatments were laid out in a randomised complete block design (RCBD). In the second study part, the 3 green manure species were evaluated for their potential to stimulate Striga seed germination in the laboratory and the field. Results showed that green manure applications significantly reduceStriga infestation, resulting in significant rice yield increases. Green manure exhibited potential to induce suicidal germination of Striga. Based on these findings, green manure  applications should be promoted especially among smallholder resource-poor farmers as a strategy for control of Striga infestation in rice fields. Additionally, croprotation using rice and C. ochlroleuca is the best option since it reduces Striga infestation and increases yield of rice

Results on a questionnaire to soil surveyors around the world related to existing soil surveys and their attributes

Seventy respondents from 40 countries replied to a questionnaire on methodologies used in soil surveys. Observations and conclusions worth noting are given. Some terminologies in soil surveys are not conceived and used consistently by soil surveyors. The nature of soil surveys is determined by soil surveyors themselves and only occasionally do users determine the nature of these documents. The most common immediate users of soil surveys are ministries of agriculture and natural resources, private farmers and land owners, engineering departments and state farms. Many soil surveyors do not monitor the utility of soil surveys to see if users are satisfied with them or not. Grid mapping is more commonly used in the very detailed inventories than in reconnaissance and exploratory surveys, while free-hand surveys are more widely used in detailed, semi-detailed and reconnaissance surveys. Detailed and semi-detailed surveys are the most often used both directly and indirectly through interpretation maps. Some of the reasons why soil surveys sometimes are not used despite their availability, include their complicated nature and insufficient knowledge about their existence. Some recommendations are given for improvement in future soil surveys.UNESC