Overview of the Status of Macro Elements, Salinity, and Organic Carbon in Some Paddy Lands of Gilan Province

Lack of awareness of changes in soil content of nutrient elements in different farms and applying the same fertilizer recommendations cause some soils to receive more, and some less, than the required fertilizer. The aim of this study was to investigate the spatial changes and status of macro elements including N, P and K and some important soil properties such as OC, EC, and pH in some paddy fields of Gilan Province. To this end, in 2018, before preparing the land for cultivation, composite soil sampling was performed from 0 to 30 cm depth of paddy fields in Masal, Rudbar, Meqdad (Khoshkbijar, Lashtnashah, Khomam) and Siahkal areas, with spacings of at least 500 m. Using the results of soil analysis, status of the desired characteristics was evaluated based on descriptive statistics. Then, excess and deficiency of nutrients in paddy lands were determined. Data analysis showed that  available phosphorus was one of the major limitations in the study areas, such that more than 80% of the sampled soils in Siahkal, 72% in Rudbar, 65% in Masal, and 54% in Meqdad were deficient in P. Potassium had better conditions than P, such that 51.3% of the soils in Siahkal area, 31% in Rudbar, 66% in Masal, and 26%in Migdad had available K lower than the critical level. Also, 19.4% of soils in Meqdad region,  36.6% in Siahkal, 48.4% in Masal, and 100% in Rudbar had total N lower than the critical level (0.2 %). Examination of the condition of paddy soils at the sampling points showed that the spatial distribution of nutrients was not the same. The findings of this study showed that using the same fertilizer recommendation is not suitable for different paddy lands; and distribution of fertilizer in different areas of the province should be done according to the soil analysis of each region.