Biology, ecology and control of Johnson grass, Sorghum halepense (L) Pers

Abstract

Johnson grass is a perennial herbaceous species of Mediterranean origin currently widespread across the globe and still on the list of harmful weeds in many countries. It is a geophyte species (G1) reproducing generatively (seeds) and vegetatively (rhizomes). The plant is able to grow over two meters in height. Individuals form between 8000 and 12000 seeds, depending on the number of panicles. The seed preserves germinability in soil for periods of up to 20 years. Germinability is highest at 20-30oC and depths of less than 12 cm. Johnson grass forms three types of rhizomes: primary secondary and tertiary. Regeneration of a rhizome cutting requires that it should include at least one intact node and two internodes. Rhizome cuttings achieve best regeneration when imbedded at five centimeters soil depth and under soil temperature of over 10 C. Johnson grass is frequent in intensive agricultural areas of Serbia, i.e. in row crops, perennial stands, stubbles ends of furrow and ruderal habitats. To control Johnson grass it is essential to observe crop rotation plans, sow pure seeding material, use well fermented manure, apply high-quality basic and other cultivation practices (aimed at exhausting plants), observe the timing, depth and density of sowing of the cultivated crops, grow clover and grass mixtures and use efficacious herbicides in rotation.

Divlji sirak (Sorghum halepense) je višegodišnja, kosmopolitska zeljasta vrsta, mediteranskog porekla. Može da izraste u visinu i preko dva metra. Jedna biljka produkuje od 8.000-12.000 semena, koja u zemljištu mogu očuvati klijavost i do 20 godina. Najbolju klijavost seme postiže na temperaturi od 20-30oC i dubini manjoj od 12 cm. Najbolju regeneraciju reznice rizoma postižu kada se nađu na dubini do pet santimetara i temperaturi iznad 10 C. To je korov okopavinskih useva, intenzivnih poljoprivrednih područja Srbije. U uslovima visoke zakorovljenosti, neophodno je sistematski primenjivati integralne mere suzbijanja.