Crop rotation, allelopathy

Weed management in organic agriculture use preventive methods such as an appropriate crop rotation, precise soiled preparation before sowing crops, narrow seed spacing, etc. (Labrada 2003). Many of them include ways in which allelopathy (often together with competition) could play an important role (Fig. 14.1). 

Mamolos AP, Kalburtji KL (2001) Significance of allelopathy in crop rotation. J Crop Prod 4 197-218... 

Rasmussen IA (2004) The effect of sowing date, stale seedbed, row width and mechanical control on weeds and yields of organic winter wheat. Weed Res 44 12-20 Reddy KC (2001) Effects of cereal and legume cover crop residues on weeds yield, and net return in soybean (Glycine max),. Weed Tech 15 660-668 Reynolds LB, Potter JW, Ball-Coelho BR (2000) Crop rotation with Tagetes sp. is an alternative to chemical fumigation for control of root-lesion nematodes. Agron J 92 957-966 Rice EL (1984) Allelopathy. Academic, New York, p 317... 

Rizvi SJH, Mishra GP, Rizvi V (1989) AUelopathic effects of nicotine on maize I. Its possible importance in crop rotation. Plant Soil 116 289-291 Roshchina VV (2001) Molecular-cellular mechanisms in pollen allelopathy. Allelopathy J 8 11-28 Roth CM, Shroyer JP, Paulsen GM (2000) Allelopathy of sorghum on wheat under several tillage systems. Agron J 92 855-860... 

Different types of management may be developed for weed, insect, and disease control, for crop rotation, and for agroforestry employing allelopathy. In the following paragraphs these are discussed separately. 

In we management systems involving allelopathy, crop varieties may be screened or new varieties developed for their potential for controlling weeds. Such varieties may be left as residues in the field, or be incori rated in every rotation system, and/or used as a companion crop. Similarly, if crop varieties allelopathic to pathogens can be found, their residues can be used similarly for disease control. Research groups of Putnam at Michigan State University and of Gliessman at the University of California are two of many that are involved in research of this kind. 

Baranenko, V.V. (2001). Pea chloroplasts under clino-rotation lipid peroxidation and superoxide dismutase activity. Advances in Space Research 27 973-976. Bhowmik, P.C. and Inderjit (2003). Challenges and opportunities in implementing allelopathy for natural weed management. Crop Protection 22 661-671. 

Much research is needed on the quantitative effects on crop yields of interference by most of our serious weeds, and on the relative contributions of allelopathy and competition to the total interference by each weed species. Crop-crop relationships need to be investigated much more thoroughly to determine which crops can follow others with the least inhibitory or most stimulatory effects. More emphasis should be placed on investigations of stimulatory allelopathlc effects, because these effects have been largely Ignored in the past. Possible autotoxicity should be investigated also to determine if it is unwise to cultivate the same crop continuously without rotation. 

---