Iranian Journal of Crop Sciences
Year:2005 | Volume:7 | Issue:2|Papers Count:7

In order to study the effect of tillage systems and row distances on yield, yield components and oil content of rapeseed cultivars (Brassica napus L.), two field experiments were carried out at the Sari Agricultural Expriemental Station, 25 km of Eastern Sari, Iran in 2001–2002 and 2002–2003. The experimental design was split plot factorial with three replications. Three tillage system levels were assigned to main plots, and combination of rapeseed cultivars (Hyola 401, PF 7045.91) and row distances (including 8, 16 and 24 cm) were randomized to sub-plots. The tillage levels were consisting of: no-tillage, minimum tillage (residual return with plough and one disk) and conventional tillage (residual return with two disks). Analysis of variance using SAS showed that tillage systems and rapeseed cultivars had significant effect on grain yield at 1% probability level. There was no difference between minimum and no tillage. PF 7045.91 also had the highest grain yield at low distance and conventional tillage (3689 kg.ha). followed by Hyola 40 in 8 cm row distance and no tillage (3164 kg.ha) cultivars differed (p<0.01) for flowering period, branch height, plant height, branch number, pod number, 1000-grain weight, grain yield, oil content and oil yield. Results also showed that more grain yield was produced in conventional tillage system, suitable cultivars are to although by used in minimum or no tillage systems with 8 cm row distance for sustainable of Agricultural systems. It is concluded that minimum and no tillage systems have some advantages over conventional tillage system.

In order to determine the adaptation and stability of grain yield in 8 rice promising genotypes as well as two commercial cultivars (Khazar and Neamat), as control, a field experiment was carried out in three locations in Gilan province during 1997 and 1998 cropping seasons. The experimental design was randomized complete block with 4 replications and planting distance was 25 cm ´ 25 cm. Analysis of variance showed significant differences for grain yield among genotypes. Combined ANOVA was also performed following Bartlett test (for uniformity of error variances). Year and location effects were considered random while genotypic effect fixed. The F test was calculated based on expected mean squares. Results showed significant differences among the genotypes. The effects of location and year and genotype´location and genotype ´year interactions were not significant. It means that the genotypes had similar response over different locations and years. However, the interaction effects of year´location, and year´location´genotype were significant. Stability of genotypes were evaluated using six different methods including: variance (S2i) and coefficient of variability (CVi) of environment (parameter no.1), coefficient of regression of mean yield on environmental index (bi) (parameter no.2), variance of deviation from regression (S2di) (Parameter no.3) and within location variance (MSy/p) and C.V. (parameter no.4). Results of these methods were different more or less; however, genotypes no.7604 and 7606 as well as Khazar and Neamat were determined as stable genotypes, because low S2i, CVi and MSy/p and bi equal to unity and low and non- significant S2di. Consequently, due to higher mean yield compared to Khazar and the desired cooking and milling qualities, these two genotypes were selected to be released.

In order to estimate the leaf nitrogen (N) status of rice plant (oryza sativa L Cv. Khazar) and to recommend the precise timing of N-fertilizer topdressing by using chlorophyll meter (SPAD-502), a field experiment was carried out in a RCBD with 6 treatments and three replications in a coastal light texture soil in Guilan province -Iran in 2003 cropping season. Six N rates using Urea T1-control (no N fertilizer), T2-40 kg/ha (Basal), T3-40+40 kg/ha (Basal + Mid-tillering), T4-40+20+20 kg/ha (Basal + Midtillering + Panicle initiation), T5- 60+60 kg/ha (Basal + Midtillering) and T6-60+30+30 kg/ha (Basal + Midtillering + Panicle initiation) Kg/ha were applied. The chlorophyll meter (SPAD) values and leaf N concentration (by Kjeldahl procedure) were determined at 9 stage: 19, 29, 39, 49, 59, 69, 79, 89 and 99 days after transplanting on the uppermost fully expanded leaf in rice plant. Regression analysis showed that, when data for all growth stages were pooled, SPAD values predicated only about 23% of variation of leaf N concentration on a dry-weight basis, but SPAD values predicated about 80% of variation of leaf N concentration on a leaf area basis. At each growth stage, SPAD values correlated with leaf N concentration on a leaf area basis better than leaf N concentration on a dry-weight basis.Thus, chlorophyll meter provides a simple, quick, and nondestructive method to estimate the leaf N concentration on a leaf area basis and can be used to predict the appropriate timing for N fertilizer topdressing in rice.

Intermediate-late and early tropical highland maize hybrids, were evaluated in two seperate experiments. Each experiment included 11 hybrids and one adapted commercial hybrids, KSC 647(medium maturity), using randomized complete block design with 3 replications and carried out in 4 locations of Iran (Karaj, Gorgan, Darab and Dezful) in 2002 cropping season. Results indicated that these type of hybrids performed better adaptation for synchronized pollen shedding and silk emergence in Darab and Dezful. These germplasm were not useful for Gorgan and Karaj, where they produced low yield due mainly to high anthesis-silking interval (ASI). Although, these hybrids are not suitable to be used directly, it would possible to use them as a knew genetic resources, especially for incorporating tolerance to early season low temperature, as they are originated from highlands.

In order to study the adaptation of Tropical and Sub-tropical hybrids in temperate conditions of Iran, two groups of tropical and subtropical maize germplasms, each including 18 hybrids and two adapted commercial hybrids, KSC 647(medium maturity) and KSC 704 (late maturity) were evaluated in two separate experiments using randomized complete block design with three replications, in 4 locations of Iran (Karaj, Gorgan, Darab and Dezful), in 2002 cropping season. In general, Sub-tropical hybrids performed better adaptation in Darab (28o and 46', latitude) and Dezful (32o and 24', latitude), comparing to Tropical hybrids, and due mainly to similarity of latitude to the origin of these germplasm. The possibility of using these germplasm in Karaj and Gorgan is low, due mainly to lower yield of these hybrids, which could be due to longer ASI and delayed flowering. In Darab and Dezful, Sub-tropical hybrids performed successful in comparison with local adapted hybrids, indicating that these germplsm can be used as new genetic resources for extraction of distinct inbred lines. Desirable performance of sub-tropical germplasm, especially in Darab, implies that they would be more promising for increasing the efficiency of hybrid maize breeding program for these regions.

To study the effect of pre-and post-anthesis water limitation on agronomic characteristics, grain yield and it’s components of hexaploid triticale (X Triticosecale wittmack), a field experiment was conducted in split plot design using RCBD, with three replications in Mashhad Agricultural Research Station in two successive cropping seasons (2001-2003). Main plots (L) were water limitation in different growth stages with 6 levels (L1: optimum conditions, L2: Water Limitation from seedling to double ridge stage (vegetative pre-anthesis), L3: Water Limitation from double ridge to anthesis stage (reproductive pre-anthesis), L4: Water limitation in post-anthesis stage, L5 and L6 received rainfall during cropping seasons with only one supplementary irrigation at anthesis or milky stage, respectively). Five hexaploid triticale genotypes (Juanillo 92 and four promising lines) were assigned to sub plots. Results showed that water deficit in vegetative pre-anthesis stage (L2) reduced grain yield, No. of grains per spike, kernels weight per spike, No. of grains per square meter, total dry weight at anthesis and seed set percentage in comparison to optimum condition (L1). However, grain yield in pre-anthesis water stress reduced less than L3 and L4 treatments. Out of four treatments (L1, L2, L3 and L4), water stress in double ridges to anthesis (L3) had the highest negative effect on grain yield (in comparison to L1 and L2 47% and 30% less grain yield, respectively) and it’s components. Water stress from double ridge to anthesis also produced minimum No. of grains per square meter (in comparison to L1 and L2 52% and 39% less grain per square mater, respectively). However, 1000 kernel weight was increased in comparison to L1 and L2.  Water stress in post-anthesis (L4) had negative effect on grain yield, 1000 kernel weight, days to physiological maturity, grain filling duration and No. of grains per square meter. Irrigation at anthesis (L5) was more effective than milky stage (L6) under natural conditions (without using rain shelter). Genotypes No.3 (Ardi-1/Topo1419//Erizo-9 CTY87-852) and No. 4 (Cargo/Ibex//Civet#2) had the lowest water stress susceptibility index (SI) and high grain yield under optimum conditions.