Sh Ayoubi, F Khormali,
Volume 12, Issue 46 (1-2009)
Abstract
Understanding distribution of soil properties at the field scale is important for improving agricultural management practices and for assessing the effects of agriculture on environmental quality. Spatial variability within soil occurs naturally due to pedogenic factors as well as land use and management strategies. The variability of soil properties within fields is often described by classical statistical and geostatistical methods. This research was conducted to study what factors control the spatial variability of soil nutrients using an integration of principal component analysis and geostatistics in Appaipally Village, Andra Pradesh, India. 110 soil samples were randomly collected from 0-30 cm and prepared for laboratory analyses. Total N, available P, Ca, K, Na, Mg, S, B, Mn, Fe, Zn were measured using standard methods. Statistical and geostatistical analysis were then performed on raw data. The results of PCA analysis showed that 4 PC's had Eigen-value of more than 1 and explained 71.64 % of total variance. The results of geostatistical analysis revealed that three PC's had isotropic distribution based on surface variogram. Spherical model was fitted to all PC's. Ranges of model were 288 and 393 m for PC1 and PC3 respectively. On the other hand the range for PC2 was significantly different (877m). The most important elements in PC2 such as Fe, Mn, and Zn probably had similar range of effectiveness (700-900m). The comparison of PC's distributions indicated that PC1 and PC3 including total N, available Mg, K, Cu, Ca and P, were in accordance with farming plots dimensions and management practices. Therefore, it is necessary to improve the appropriate fertilizers used by farmers. The pattern of PC2 distribution was not consistent with farmer's plots, but had the best concordance with soil acidity. Therefore, the most correlated elements with this PC including Fe, Mn, and Zn are mainly controlled by soil acidity and not affected by management practices. However, spatial variability of these elements in areas lower than critical values should be considered for site-specific management.
A Bahri, Gh Azari Takami, A Keyvan, Gh Vosoghi,
Volume 13, Issue 48 (7-2009)
Abstract
Immunostimulants are one of the important ways to prevent diseases. The vaccination and immune system stimulator and their combination can increase the ability of vaccines in prevention of diseases and improved indexes of growth and survival rates in shrimps. In this research, the separate and simultaneous effects of Ergosan and Vibromax vaccine on the growth factors such as total length and increasing of dry weight and survival rates in three stages of post larvae PL1,PL5 and PL15 in Indian white shrimp (Fenneropenaeus indicus ) were studied. The feeding of vaccine to shrimps was done through Artemia nauplii ( Artemia franciscana) enrichment. The effects of Ergosan (T1) and effect of Vibromax (T2) separately and in combination (T3) along with a control treatment for comparison were studied. Taking into consideration of 4 treatments and 3 replications for each of them, 12 similar vessels were used, which were refilled with 10 liters of water and reserved with 100 larvae in liters in zoa stages and were fed in a completely randomized design. Duration of experiment was from zoa stage to PL15 and in the end of 12, 16 and 25 days they were analyzed for the biometry and determination of survival rates. Results showed that the highest amount of total length (mm) was observed in PL1,PL5 and PL15 stages in T3 (5.26, 6.45 and 18.41) and was a little different from that in T1 (5.28, 6.32 and 17.94) which was significantly different from the control treatment ( 4.91 , 6.09 and 17.36 ) at P<0.05 level. Furthermore, T2 (5.11, 6.07 and 17.44) and control treatment were not significantly different (P>0.05). The highest amount of dry weight (mg) was observed in PL1, PL5 and PL15 stages in T3 (0.296, 0.890 and 2.940). In contrast to the control (0.216, 0.640 and 2.875) it was significantly different (P<0.05).The highest amount of survival rates (%) was observed in T3 (77.33, 76.33 and 80.67) which unlike control treatment (57, 57.33 and 59.67) was significantly different (P<0.05). The use of these two products in a desired feeding program from zoa stage to PL12 could increase the resistance and immunity in post larvae and survival rates and growth factors in shrimps leading to produce suitable post larvae for introducing into the training ponds.
