A field study was conducted to evaluate the effects of shatter cane (Sorghum bicolor) and soybean (Glycine max) densities on soybean seed yield and to quantify interspecific and intraspecific interference coefficients. The relations between soybean seed yield per plant and shatter cane density at different densities of soybean and also with soybean density at different densities of shatter cane are well described by the reciprocal equations. Soybean seed yield per unit area decreased with increasing shatter cane density. The highest yield loss (57%) was relative to 50 and 12 plants/m 2 of soybean and shatter cane densities, respectively. Optimum soybean densities on the basis of maximum soybean seed yield per unit area at 0,4, 8, and 12 plants/m 2 of shatter cane were achieved at 50, 34, 32, and 36 plants/m 2 , as estimated by the asymptotic or parabolic relations between soybean seed yield per unit area and soybean densities at different shatter cane densities. Shatter cane was a stronger competitor than soybean, as a shatter cane plant was equal to 2.5 soybean plants, based on soybean seed yield. In contrast, a soybean plant was equal to 0.18 of a H03096;

In order to evaluate seed development and quality of maize (Zea mays) cultivars ('DC-370' , 'SC-500' , 'OSSK-602' and 'SC-604'), a split plot experiment (using R.C.B. design) with three replicates was conducted in 2009 at the Research Farm of the Faculty of Agriculture, University of Tabriz, Iran. Seeds were harvested at five day intervals in eight stages. Subsequently, the quality of seed samples was determined in the laboratory. Germination percentage and seedling dry weight were enhanced, but electrical conductivity of seed leachates was reduced with increasing seed weight on mother plant. Maximum seed quality of maize cultivars was attained at the end of seed filling phase. Seed quality at earlier harvests was low, because of immaturity. Differences in maximum seedling dry weight of maize cultivars were attributed to variation in genetic constitution. It was concluded that in maize cultivars, maximum seed quality could be achieved at physiological maturity.

Methodologies of competitive interaction quantification between crops are not widely investigated. Therefore, field experiments (using addition series) were conducted in 2005 and 2006, to quantify interspecific and intraspecific competition coefficients and, also, the relative competitive ability (RC) of potato (Solanum tuberosum) and common bean (Phaseolus vulgaris). The relations between potato tuber yield/plant and common bean density at various densities of potato and also with potato density at different densities of common bean are well described by the reciprocal equations. Potato tuber yield/unit area decreased as common bean density increased. Optimum potato densities on the basis of maximum potato tuber yield/unit area at 0, 20, 30, and 40 plants/m 2 of common bean were obtained at 14, 13, 12, and 12 plants/m 2 , as estimated by the parabolic relations between potato tuber yield/ unit area and potato densities at different common bean densities. Potato was a stronger competitor than common bean, as a potato plant was equal to 6.22 common bean plants, based on potato tuber yield. A common bean plant, also, was equivalent to 0.0475 of a potato plant, on the basis of common bean grain yield. Therefore, potato was more aggressive than common bean, indicating that potato tuber yield was mostly affected by intraspecific competition, whereas common bean grain yield was mostly affected by interspecific competition. Niche differentiation index (NDI) was smaller than 1, showing severe competition of two species for environmental H08057; resources. It was concluded that yield-density relations in intercropping could be well quantified by application of the proposed equations.

A sub-sample of maize (cv. KSC301) seeds was kept as control or vigorous seed lot and two other sub-samples with about 16% moisture content were artificially deteriorated at 40C for 16 and 18 days. The three seed lots had seed viabilities of 99% (V1), 91% (V2) and 79% (V3). Laboratory tests were carried out as CR design with four replicates. However, the field experiment was conducted as factorial based on RCB design with three replicates to investigate the performance of differentially deteriorated seed lots under four irrigation treatments (irrigation after 70, 90, 110 and 130 mm evaporation from class A pan). Germination and emergence times significantly increased with increasing seed deterioration, but mean viability percentage, seedling dry weight, seedling emergence and protein and grain yields decreased as seed deterioration increased. Even plants from less deteriorated seed lot (V2) with acceptable germination (91%) showed 25.1% reduction in grain yield per unit area. The superiority of V1 to V2 seeds of maize increased as water limitation increased. Protein yield was also decreased as a result of seed deterioration. Seedling dry weight highly correlated with the field emergence and grain and protein yields. Thus, it is necessary to produce and cultivate high vigor seeds of maize, in order to ensure satisfactory yield achievement, particularly under adverse environmental conditions.