SUMMARYDuring the 2006-2007 period, the allelopathic effect of cold water extracts from Amaranthus retroflexus L., Chenopodium album L., Erigeron canadensis L. and Solanum nigrum L. on seed germination and initial development of Glycine max L., Pisum sativum L. and Vicia sativa L. was studied under laboratory conditions in the Institute of Forage Crops, Pleven. It was found that: water extracts from fresh and dry biomass of A. retroflexus, Ch. album, E. canadensis and S. nigrum had an inhibitory effect on seed germination of G. max, P. sativum and V. sativa, the inhibition rate for the extracts from fresh biomass varying from 28.8 to 81.5% and for the extracts from dry weed biomass it was from 26.8 tо 89.2%; The values of LC 50 varied from 13.5 tо 72.2 g l -1 for the extracts from fresh biomass and from 7.0 tо 84. 1 g l -1 for the extracts from dry weed biomass and they could be conditionally grouped in the following ascending order: A. retroflexus < S. nigrum < E. canadensis

Twelve genotypes (varieties, hybrids, mutant and hybrid lines) of sorghum (Sorghum bicolor (L.) Moench) were studied. The objective of the study was to determine the popping performance and to establish the relationships with some biochemical parameters (content of crude proteins, starch, moisture) and grain characteristics (pericarp color, grain width, 1000-grain weight). Popping yield of sorghum grain genotypes was in range 32.0% -72.0%. The highest influence on popping yield had 1000-grain weight (r = 0.831), starch content (r = -0.356), followed by moisture content (r = 0.212) and crude proteins (r = 0.282). It was found that the endosperm of the seeds expanded poorly in most genotypes with white coloring of the pericarp (from 33.3 to 90.1%), while for those with a dark-colored seed pericarp, the expansion was from 50.0% to 160.0%. Mutant line M1 (6282) (dark brown color of the pericarp) and hybrid line 1643 (white color of the pericarp) stood out with relatively better popping characteristics and particle size of popped grains. This study demonstrated one of the qualities of sorghum grain-poppability and opportunities for enrichment of the genetic diversity for the breeding program in this culture.

SummaryAllelopathic effects of aqueous extracts of Sorghum halepense L. (Pers.) on seed germination and primary seedling growth and development of two lupine species was studied. Lupinus albus and Lupinus luteus showed different levels of susceptibility to the allelopathic effect of weed extracts. Increasing concentrations (1.25, 2.50, 5.00 and 10.00%) of extracts from aboveground and belowground biomass suppressed seed germination of L. luteus from 53.2 to 74.7%. The germination of L. albus seeds was unaffected, except by the highest concentration of 10.00%. Fresh biomass accumulation in the initial germ of L. luteus was inhibited by 3.8-40.3% under the effect of concentrations of 2.50, 5.00 and 10.00%, which made the species susceptible to S. halepense extracts. L. albus was tolerant as it was not found to sustain a significant allelopathic effect of the extracts.

SUMMARYRumex crispus L. is an invasive species widespread in our country and in particular in the region of North Bulgaria. It is characterized by high biological and ecological plasticity. Owing to its great reproductive potential, the weed has been assigned to the list of economically most important weeds in the country.With the purpose of studying the possibility of chemical weed control in noncropped areas with heavy natural background infestation with R. crispus L. and other dicotyledonous weeds, two field trials were carried out. A ready-to-use herbicide mixture 2,4-D 140.2 g/l -1 + Triclopyr 144 g/l -1 , trade product Genoxon 3X (X0050), was tested at two doses of active ingredient, 3552 and 2842 ml/ha -1 . It was found that: (1) population density of Rumex crispus L. can be successfully reduced by treatment at the stage of early stem formation; herbicide efficacy with 3552 and 2882 ml/ha -1 doses on the 21 st day after treatment was 100% and 90.5%, respectively, at the end of vegetation 94.4 and 85.7%, respectively; (2) herbicidal efficacy was lower when R. crispus L. was treated at the 5 -6 leaf stage, being 100 -94.1% and 80 -76.5% respectively for the indicated doses and time of recording; (3) at the studied doses the herbicide controlled both annual dicotyledonous weeds (Amaranthus spp., Chenopodium album L., Portulaca oleracea L.) and perennial dicotyledonous ones (Cirsium arvense L., Sonchus arvensis L., Convolvulus arvensis L., Carduus acanthoides L.), but it was not toxic to monocotyledonous weeds.

This paper aimed at providing popping characteristics of different red and white sorghum genotypes according to different moisture content at traditional methods of popping using high temperature for a short time (HTST). To increasing grain moisture level, seven sorghum genotypes - mutant and hybrid lines (M1(6282), 16113, 16121, 1641, 1643, 1651, 1673) were soaked to 0, 60, 120 and 180 min in distilled water. The popping rate and expansion ratio were recorded. The results showed that conventional method of popping is a good main to produce pops sorghum after increasing moisture of grains. Moistening of grains from 13-16 % increased 5.3-10.2% popping rate of all sorghum genotypes. The mutant line M1(6282) with red coloration of pericarp had the highest popping rate and expansion ratio at 16% moisture i.e. 85% and 3.88 %, respectively. There was correlation between diameter of grains and parameters expansion ratio (from 0.604 to 0.724), popping rate (from 0.815 to 0.878) and moisture grains (from 0.815 to 0.878).