The effect of soil temperature, moisture and nitrogen on Striga asiatica (L.) Kuntze seed germination, viability and emergence on sorghum ( Sorghum bicolor L. Moench) roots under field conditions uri icon

abstract

  • Experiments were conducted in a Striga-sick field to study the effect of soil tempcriiture, moisture andnitrogen on Striga parasitism on sorghum. Striga seeds contained in nylon bags and buried at 2 em inthe soil, were exposed to different tcmpcraturc and nioisturc treatments. Clear polythenc, hay rnulchand bare soil treatments were used to vary soil temperature. These treatments gave mean maximumtemperatures of 60°, 48" and 37°C. respectively at 2-cm soil depth. Irrigation levels of 0 , 30 and 00 mmwcre applied to change soil moisture. Strigi~ seed germination, viability and emcrgcnce were studied.After 34 days of preconditioning, the exhumed Striga sccds from polytlienc-covered plots (solarizedplots) did not germinate or retain viability when thcse seeds wcrc exposed to sorghum root exudate.However, seeds sin~ilarly buried under hay mulch or barc soil, with mean maximum soil temperaturesof 48" and 37"C, respectively, had similar germination and viability percentages. Of these 75%germinated and 85% of them were viable, regardless of the temperature treatment. Although seedsstored at high tcmperaturc and humidity (solarization) wcre killed, more Striga plants cmcrged underthe polythenc treatment compared to hay mulch and barc soil treatments. The observed Striga plants inthe polythene mulch treatment were, therefore, assumed to have come from deeper layers wheresolarization was not effective. Irrigation treatments did not have significant effects on Striga seedgermination and viability, but a slightly higher numbcr of plants cmerged at 60-mm irrigation level thanat 30-mm and 0-mm. Striga emergence, on the other hand, was directly related to the rate of Napplication. Nitrogen rates of 0, 25, 50 and 100 kg h a ' resulted in the emergence of 11, 34, 38 and 40Striga plants per plot, respectively. Despite the high infestation at high N levels, sorghum plahts did notshow a loss of vigor. Nitrogen application, therefore, does not reduce Striga incidence, but seems toneutralize the harmful effects of Striga without reducing the extent of parasitism

publication date

  • 1991
  • 1991