A slow-release nitrogen fertilizer was prepared by covalently immobilizing urea on a biodegradable acrylic acid based polymer matrix. Polyacrylic acid was prepared by solution polymerization of acrylic acid followed by covalent immobilization of urea through the activated carboxyl groups. The resulting product, termed as polyurea, was characterized by FTIR and NMR spectral analyses, thin layer chromatography measurement and elemental analyses. Results showed that polyurea contained 24.76% nitrogen and the solvency reduced to over 300 times as compared to urea. To clarify the performance of this polyurea in agriculture, a comparative study was then carried out on the growth of green chili Capsicum annuum plants using urea and control (no nitrogen fertilizer) as the basis. Polyurea showed improved yield in terms of average plant size over the cultivation period. The nitrogen release behavior in soil during cropping and plant uptake of nitrogen suggested that polyurea can be used as slow-release nitrogen fertilizer.

green chili plants --- nitrogen --- urea --- polyurea --- Slow-release

This research was initiated with the aim at finding varieties of Potato that can respond to graded levels of NPK fertilizer and form of seed tuber. The treatments tested consist of four rates of NPK fertilizer (0, 300, 600 and 900 kg ha^-1), two forms of seed tuber (whole and cut-tubers) and four varieties of Irish potato (Greta, Nicola, RC 767-2 and WC 732-1). A split-plot design was used in which the factorial combinations of fertilizer rate and form of seed tuber were assigned to the main plots while the varieties occupied the sub-plots. The treatments were replicated three times. Varieties Nicola and RC 767-2 had the heaviest and least leaf and stem dry weights, respectively. Nicola, RC 767-2 and WC 732-1 produced more tubers and unmarketable tuber yield than Greta. Greta and RC 767-2 produced larger tubers than Nicola and WC 732-1. The highest NPK rate of 900 kg ha^-1 resulted in the heaviest leaf and stem. Optimum tuber number and size was attained at the higher fertilizer rate of 600 kg ha^-1. Further increase above 600 kg NPK ha^-1 depressed tuber number and tuber weight in 1997/98 and tuber size in 1998/99. The same 600 kg NPK ha^-1 recorded the least unmarketable tuber yield. None of the factor measured was affected by type of seed tuber. In conclusion RC 767-2 had the highest plant dry weights as well as more tubers and unmarketable tuber yield that were comparable to that of Nicola and WC 732-1. Greta and RC 767-2 had larger tubers than the other two varieties. The plant dry weights were optimized at 900 kg NPK ha^-1 while more tubers of larger size were maximized at 600 kg NPK ha^-1. The medium NPK rate of 600 kg ha^-1 had least unmarketable tuber yield. Planting of either whole or cut tuber sett did not affect any of the parameter.

unmarketable tuber yield component --- form of seed tuber --- Fertilizer rate --- Irish potato

To study the effect of organic and chemical fertilizers on forage yield and quality in globe artichoke (Cynara scolymus L.) an experiment was conducted using a randomized completed block design (RCBD) with four replications at the Research Farm of College of Agriculture, University of Tehran, Karaj, Iran in 2006. The treatments included five levels of chemical fertilizers, four levels of manure, five levels of mixture of different ratios of chemical fertilizers and manure (integrated system) and a control treatment without any fertilizers. Fertilization treatments significantly affected forage quantity and quality of artichoke. For chemical fertilizers, total DM yield was increased to 4.13 and 3.7 t ha^-1 by the treatments (kg ha^-1) N₂₀₀/P₂₀₀/K₂₄₀ and N₁₆₀/P₁₆₀/K₁₉₂, respectively. For organic systems, the highest yields of 2.86 and 2.77 t ha^-1 were obtained by treatments of 30 and 40 tones of cattle manure/ha, respectively. In the integrated system, the highest DM values of 4.86 and 4.06 t ha^-1 were obtained in treatments N₈₀/P₈₀/K₉₆/manure_20,000 and N₁₂₀/P₁₂₀K₁₄₄/manure_10,000, respectively. The effects of three soil fertilization systems on forage quality traits were inconsistent. Chemical and integrated systems increased crude protein (CP), K and P contents in globe artichoke. For dry matter digestibility (DMD) there were no significant differences among fertilizing systems, although all of them produced higher DMD compared to control. For water-soluble carbohydrates (WSC), the positive effect of organic fertilization was higher than in the other two systems. It was concluded that artichoke, as a new forage crop, has a good yield and quality potential for livestock feeding in terms of soil fertilization systems But further studies would be needed for considering of Artichoke as a new source of forage crops.

quality traits --- forage yield --- Artichoke (Cynara scolymus L.) --- soil fertilizing systems

In order to investigate of rice and barnyard-grass in different levels of herbicide and crop density, an experiment was conducted in split plot design with four replicate, in research farm of Ramin Agriculture and Natural Resources University in 2006. Four herbicide doses (0, 3, 5 and 7 L ha^-1) was arranged in main plots and three seeding rates (100, 120 and 140 kg seed ha^-1) in subplots. Interaction of herbicide and crop density on dry matter and yield of rice and barnyard-grass was significant. Therefore, response of variance trends of these traits to herbicide in different densities was different. While no herbicide was be used, rice yield in density 120 was higher than other densities, that showed that optimum crop density could increased crop competition ability and decreased herbicide use. In other hand, it be observed that highest and lowest yield of crop and weed, respectively, was be related to 5 L herbicide ha^-1. In this case, there was little difference between different densities. With more herbicide use, probably due to toxicity effect, crop yield decreased. However, in this herbicide dose, density 120 showed lesser changes in crop yield. In density 120, crop and weed yield relationship have lesser slope in comparison with other densities. Ultimately, it seems that optimum crop density can lessen crop sensitivity to other environmental and agronomic factors including weed competition and herbicide use.

herbicide --- direct seeding --- crop density --- Barnyard-grass --- rice --- yield