JWSS - Journal of Water and Soil Science

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The effect of N levels and planting densities on quantitative and qualitative characteristics of grain yield in grain sorghum (cv. Kimia) was studied in summer 1998 at Kushkak Agricultural Research Station, Shiraz University. The experiment was a spilt plot with 4 replications in which 4 levels of planting densities (7.7, 10, 15.4, 20 seeds m^-2) were applied as main plots and 4 levels of N (0, 40, 80, 120 Kg N ha^-1) as subplots.

 N application rates up to 120 kg N ha^-1 increased grain yield (7240 kg ha^-1), but due to increased planting density (5336 kg ha^-1) the highest yield obtained from 15 seeds m^-2. Interaction of N and planting density was also significant. Application of 80 kg N ha^-1 and highest planting density produced 8702 kg ha^-1 of grain. Different grain yields in different levels of N and planting densities were due to increased number of grains per basic branches of panicle and increased number of panicle per m^-2. The trend of variation of crop growth rates (CGR) was similar to the trend of grain yield. Nitrogen application increased grain protein contents but planting density had no significant effect on grain protein. Phenolic compounds (tannins) decreased with increasing N application and with decreasing planting density. A negative correlation was observed between increased N content and increased phenolic compounds.

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Drought stress is one of the major limiting factors of crop yield. A field experiment was conducted to study the effects of drought stress on yield and yield components of nine bread wheat and one durum wheat genotypes during 2003-2004 growing season. The experiment was designed as two separate randomized complete blocks design with three replicates under well-watered and unwatered conditions during the post-anthesis period. Post-anthesis drought stress reduced the grain yield and yield components in all genotypes. Mean of each trait significantly(p≤%5) decreased under drought stress conditions, except for spikeletes number per spike and ear number per square meter. The highest yield loss was caused by the grain number per ear and 1000- grain weight reduction under drought stress conditions.“Gahar” genotype had the highest grain yield (4149 kg/ha) under drought stress conditions, whereas the highest grain yield (6674 kg/ha) was obtained for “Nikenejad” genotype under optimum conditions. Based on stress susceptibility index, “Koohdasht” and “Boholh-15” genotypes showed the lowest and the highest yield loss in response to drought stress, respectively. Correlation analysis of yield and yield components indicated that, under drought stress conditions, ear number per square meter (r=0.751) and biological yield (r=0.707) had the highest correlation with the grain yield(p≤%5), whereas these traits were grains number per ear(r=0.864) and biological yield (r=0.848) for the well-watered conditions. Therefore, it might be possible to select genotypes for greater grain yield with the means of the traits which have the highest correlation coeficient with the grain yield under each moisture regime. Generally, it appeared that “Gahar”and “Nikenejad” genotypes with greater yield potential might be recommended for agronomic conditions similar to the present investigation.

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Understanding the nitrogen remobilization by plant, in order to obtain cultivars with higher quality, has specific importance in plant physiology. In this experiment, a bread and a durum wheat cultivar, were treated with different rates and times of nitrogen application, by using split factorial on the basis of randomized complete block design with three replications at Shiraz region during 2001-2002. Main plots consisted of two levels of cultivars ( Falat and Yavaros) and sub plots included nitrogen (40, 80 and 160 (kg ha^-1) and times of nitrogen application (T1= all N fertilizer at planting , T2= 1/2 at planting + 1/2 during stem elongation and T3= 1/3 at planting + 1/3 during stem elongation + 1/3 at heading stage). The results showed that there was a significant difference between cultivars in flag leaf nitrogen content at maturity stage, N remobilization and its efficiency from flag leaf to grains and also grain protein percentage. Durum wheat was more efficient in nitrogen remobilization and therefore, had a higher grain protein percentage. Increase in rates and times of nitrogen application had significant effect on most of the measured traits. There were significant interactions between cultivars, rates and times of N application, indicating that durum wheat was more efficient in N remobilization from flag leaf to the grain. It appeared that N remobilization efficiency was the important factor affecting the grain protein percentage. Also increases in yield are associated with corresponding decreases in wheat protein.

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A study was conducted in 2007 to investigate the effect of nitrogen fertilizer rates (0, 30, 60 Kg ha-1) on some agronomic characteristics, seed yield and oil percentage in three Sesame(Sesamum indicum L.) cultivars (Dashtestan, Darab 14, and Zarghan) in Kaki region (Bushehr Province). The type of design was completely randomized block with factorial arrangement and three replications. Nitrogen(N) fertilizer had a very significant effect on agronomic characteristics, such as number of capsules in the main stem, number of capsules per plant, branches /plant, biological yield, seed yield ,and oil percentage, but had no effect on 1000 seed weight. There was no significant difference between the application of 30 and 60 Kg of N fertilizer ha-1 with respect to harvest index. Seed yield increased as N rate increased, but each cultivar had a different response to different rates of nitrogen. Dashtestan and Zarghan had superiority over Darab 14 with respect to overall agronomic properties such as response to fertilizer and early maturity, but from the qualitative point of view, Darab 14 produced higher percentage of oil.

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The optimum levels of soil moisture and nitrogen are important to obtain higher yields. To investigate the effects of water stress, nitrogen levels and application times on yield and yield components of sunflower (Helianthus annuus L.), the cultivar Euroflor at different growth stages, a two year study (2006-007) was conducted at Research Fields of College of Agriculture, Shiraz University (Badjgah) using a split factorial design with four replications. Treatments were water stress at three levels, (non-stress and stress at flowering and seed formation) as main plot and three N levels (0, 70, 140 kg ha-1) and N application times (split application at planting and stem elongation, planting and heading, and stem elongation and heading) as subplot. Number of seed per head, 1000-seed weight, seed yield, Oil yield and HI were measured. Results showed that the effects of water stress and N rates on yield and yield components were significant, but the effects of N application times and interaction between water stress, nitrogen rates and application times were insignificant. Overall, the crop showed more sensitivity to drought stress at flowering time, and 70 kg N ha-1 is recommended for the region.

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Crop residues are beneficial substances that can bring about important changes in soil biological, chemical and physical properties and can also increase or stabilize crops yield. A field experiment was carried out at Research Station of College of Agriculture, Shiraz University, Shiraz, Iran, to determine the effects of wheat (Triticum aestivum L.) residue rates in combination with N levels on some soil properties in common bean (Phaseolus vulgaris L.) cultivation for two years (2008-2009). The experiment was conducted as split split-plot arranged in a completely randomized blocks design with three replications. Treatments were two red bean cultivars as main plots, N levels (0, 34.5, 69, and 103.5 kg ha-1) as sub-plots and residue rates (0, 25, 50 and 75%) as sub sub-plots. The results showed that application of crop residues significantly increased soil organic carbon, N, K, and P contents. Heavy crop residue (75%) application had no effects on these soil properties. Thus, retaining 50% crop residue was optimum for proper soil quality. Increased N application increased soil N, decreased P and K contents, and had no effects on organic carbon.

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As there are some health and environmental concerns about wastewater, dewatered sludge, increase in green waste, and restricted legislation about burning them outdoors, environmental health engineers are investigating to find a simple, cost effective and efficient method. This is aimed to have healthy, safe and sustainable disposal of such materials. Co-composting of sludge and green waste is a newly developed process which can help us to achieve this goal. This study was to investigate the most suitable ratio of dewatered sludge to green waste from Chonibieh wastewater treatment plant in Ahvaz, Iran, and assess the feasibility of co-composting of this waste. So, dewatered sludge was composted with green waste as a bulking agent in three different ratios (1:1 ,2:1 ,3:1 : green waste: dewatered sludge W:W). Then composting proceeded in pilot vessels (M1, M2, M3) for 23 days. The C/N ratio, the percentage of total nitrogen, phosphorus, total organic carbon, humidity and pH were tested in certain periods and compared with the national standards. This study showed that in M1, M2, M3 pilots, all parameters (except for total phosphorus) including C/N ratio, percentage of total nitrogen and total organic carbon, humidity, pH could meet class 1 national standard in Iran. Moreover, this compost product could meet the EPA microbial standards, class A. So, the product of this compost process is completely stabilized and could be used in agricultural lands.