Comparison of paddy yield and soil qualitative characteristics among different agricultural systems in three regions of Mazandaran

Organic cultivation of rice (Oryza sativa) has been carried out in some parts of the world. Despite a lot of research, policy and public attention, only a small portion of the total agricultural land is cultivated as organic farming. Due to the adverse effect of conventional agriculture on environment throughout the excessive use of chemical inputs, the importance of considering to alternative agriculture is increasing day by day. One of the pillars of sustainable agriculture is the use of organic fertilizers in agro-ecosystems with the aim of eliminating the use of chemical fertilizers. Since the emergence of organic rice cultivation in Mazandaran province and the existence of numerous potential for transition from conventional to organic agriculture, the present study was designed to evaluate the paddy yield and qualitative characteristics of paddy soil in three cropping systems of conventional, low-input and organic farming. In order to study the effect of different agricultural systems on paddy yield and qualitative characteristics of paddy soil, an experiment was conducted during 2015 and 2016 in three different regions of Mazandaran province including Amol, Babol and Fereydounkenar. For organic, low-input and conventional agricultural systems, three, four and six fields were selected in these cities, respectively. Selected fields have been used the same agricultural system for at least three last years. In organic agricultural systems, poultry manure and biofertilizers including: Azotobacter and Barvar2 were used and pests and diseases controlled using Trichogramma bee, sex pheromones, fungicides and biological insecticides. Also, the weed in organic system weeded manually. In low-input system, external inputs such as chemical fertilizers and pesticides were minimized as compared to the conventional system. At the beginning of the growing season, the necessary justification was done with farmers. In each agricultural system and region, grain yield, biological and harvest index were determined in three replications. Also, in order to measure the quality of soil in each system, 10 separate samples were taken from depths of 0 to 30 cm. Nitrogen was calculated by kjeldahl method, phosphorus by Olson-Summers method and potassium by ammonium replacement method. Data was processed by excel software and after analysis of Bartlett test for uniformity of variances, mixed analysis was done using SAS statistical software ver. 9.1. Also, the mean comparison was done by Duncan's multiple range test at 5% probability level. the results showed that the highest paddy and biological yields was obtained in Fereydounkenar region and in low-input agricultural system which differed 4.73 and 2.80 percent and 29.9 and 29.12 percent as compared to the conventional and organic systems, respectively. The amounts of harvest index in organic, low-input and conventional systems were 37.48, 38.69 and 36.85 percent, respectively. However, there was no significant difference between organic and low- input systems. Also, agronomic systems positively affect the soil quality characteristics. Soil pH in organic farming system ranged from 7.39 in the first year to 7.20 in the second year which showed a decrease 2.57 percent. In low-input and conventional systems, the increase in pH was 0.92 and 1.15 percent in the second year, respectively. The maximum organic carbon content with 2.25 percent was belonged to organic system and the lowest amount (1.67 percent) was recorded in conventional system in the second year. The total nitrogen content in the conventional system decreased from 0.21 percent in the first year to 0.18 percent in the second year which showed a decrease of 14.28 percent. Also, this rate was reduced by 5 percent in low-input system in the second-year and increased by 5 percent from 0.19 to 2.0 percent in organic system in the second year. The maximum available phosphorus i.e. 14.98 mg/kg was obtained in organic system which showed a significant difference with the low-input and conventional systems with 8.34 and 13.75 percent, respectively. The amount of available potassium in organic system in first year was lower than conventional and low-input systems with 17.67 and 56.68 percent and this difference was 21.25 and 4.6 percent in the second year, respectively.