A three-year ®eld experiment was undertaken to evaluate the effects of tillage methods on grain yield and yield components of wheat (Triticum aestivum) in continuous cropping. The experiment was conducted on a Ramjerd, ®ne, mixed, mesic, typic Calcixerepts soil. Wheat was sown: (1) after burning residues followed by conventional tillage, (2) after complete residue removal followed by conventional tillage, (3) after soil incorporation of residues followed by conventional tillage, (4) into untilled residues, (5) using chisel seeder after ®eld irrigation, (6) using chisel seeder plus herbicide application, and (7) after disking. Residue burning and removal increased spikes per square metre, grain per spike, 1000±grain weight, grain yield and harvest index compared with other treatments. This was due primarily to weed interference and lack of uniform crop establishment in the presence of residues. Reduced tillage methods retained more residues on the soil surface, which provided unsuitable conditions for crop emergence and growth. The incorporation of residues led to a build up of carbon in the soil, with lower grain yields compared with residue burning and removal, but these yields were higher than those of chisel-seeded plots.

Heritability in the broad sense and correlations were determined for six agronomic traits in cowpea (Vigna sinensis L.) using four parental and six JP 2 lines. Heritability values were found to be 75, 64, 47, 44, 35 and 15% for 100-seed weight, number of seeds per pod, number of clusters per plant, number of pods per plant, yield per plant and number of branches per plant, respectively. All of the traits studied, except number of branches per plant, showed positive significant correlations with yield. It is concluded that, for yield improvement in cowpea, number of pods per plant and number of seeds per pod have selective value equal to seed yield per plant, whereas 100-seed weight and number of clusters per plant have less selective value and number of branches per plant has no selective value.

A karyotypic study was performed on 19 Echinops species in Fars Province, Iran. The taxa revealed chromosome counts of 2n= 28, 30, 32 and 34. Somatic chromosome numbers of 18 species are reported for the first time. Using somatic chromosome number as a criterion for section delimitation, the transfer of E. gedrosiacus, E. cyanocephalm and E. sojakii from Sect. Oligolepis to Sect. Ritropsis is suggested. Differences in basic chromosome numbers point towards the possible role played by centric fusion/fission in the karyotypic evolution of the genus. The Karl Pearson coefficient of correlation and principal components analysis indicated the occurrence of structural changes in chromosomes. The species occupied classes 1A, 2A & 2B of Stebbins' karyotype classification, indicating the presence of a primitive symmetrical karyotype in the genus.

The effect of soil water potential of the root media on the vegetative growth, seed and oil yield of sunflower (var. Record) grown in containers under field conditions was investigated.The weight of shoots and the total leaf area of plants before flowering significantly decreased with decrease in the water potential of the root media. There was a sharp reduction of shoot weight as the potential decreased from -0-32 to -1-25 bars and then a further slow decline as soil water potential dropped to -8'6 bars. There were no significant differences in the 100-seed weights and percentage.of oil among the treatments, but the total number of seeds was significantly different.The data did not indicate the existence of a threshold water potential above which yield was independent of soil water potential, but rather that yield was a continuously decreasing function of soil water potential.

The relationship between P and Fe in nutrition and development of plants have been studied in detail for some crop species. However, there is no such report available on cowpeas (Vigna sinensis L.). This study was initiated to investigate the effects of P and Fe on growth and mineral contents of cowpeas in two arid region soils. Cowpeas were grown for 8 weeks in two soil types (Typic Xerofluvent and Xerollic Xerochrept) from two locations (Airport and Kooshkak, respectively) containing various levels of P (0, 50, 100, and 200 ppm) and Fe (0, 5, 10, and 20 ppm). Airport soil (loam) had high soluble salts, high exchangeable Na and low organic matter, N, Fe, Zn, and Mn as compared to Kooshkak soil (silty clay). Symptoms of Fe deficiency developed only on plants growing in the Airport soil when no Fe was applied. With the application of Fe as little as 5 ppm, the symptoms were prevented. The dry matter yield of plants grown in the Airport soil was significantly lower than that grown in Kooshkak soil under all treatments. Best plant growth was obtained when 50 or 100 ppm P were added to each soil; however, no Fe was required in the Kooshkak soil while 20 ppm Fe were needed in Airport soil for optimum growth. The mineral contents in the tops of plants grown in either soil type were affected differently with increased levels of applied P or Fe. Significant interactions were observed between P and Fe treatments for most of the characteristics measured.