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General Concepts

Introduction

Long-term use of chemical fertilizer in order to supply the nutrients needed by the plant has led to reduced fertility and disruption of soil biological activity and pollution of non-renewable resources. Due to the destructive effects of chemical fertilizers excessive use, it is necessary to gradually reduce the use of these inputs and replace them with organic fertilizers. On the other hand, water deficiency has emerged as a serious crisis in recent years. Water is the first and most basic factor for the producting agricultural crops.

Challenges and necessity

The use of organic manures in agriculture would supply soil nutrients and improve the physical and chemical properties of paddy soil, as well as growth improvement. It also increases grain yield. Rice is the largest consumer of water among all agricultural crops and its irrigation efficiency is lower than other cereals. Looking for solutions to increase the production capacity of the crops as a unit of water consumption is necessary. Organic manures can play an important role to prevent water loss in paddy fields by gradually absorbing and releasing moisture. Regarding the current crisis in water resources and the need of appropriate solutions to reduce the use of chemical fertilizers, protect water and soil resources from pollution and healthy-organic rice production, research in this field seems to be necessary.

Research hypotheses

  1. Do the use of organic manures’ application and different levels of irrigation intervals cause significant changes in rice yield and its components?
  2. Do the use of organic manures application and different levels of irrigation intervals cause significant changes in physical and chemical properties of paddy soil and the uptake amount of nutrition elements in grain and rice straw?

Objectives

  1. To study the effect of organic manures application and irrigation levels on rice quantitative traits.
  2. To study the effect of organic manures application and different levels of irrigation intervals on some physical and chemical properties of paddy soil and concentration of of nutrition elements in grain and rice straw.
  3. To study the interaction of organic manures application and different levels of irrigation intervals on rice quantitative traits.
  4. To study the interaction of organic manures application and different levels of irrigation intervals on some physical and chemical properties of paddy soils and concentration of nutrition elements in rice grain and straw.

Materials and methods

In order to investigate the effect of organic manures’ application and different levels of irrigation intervals on quantitative trait of rice (Hashemi) and some physical and chemical properties of paddy soil, this experiment sketched as split plots based on randomized complete blocks design with three replications implementing for two years (including two periods of rice cultivation).The main plots in this experiment consists of different irrigation intervals at four levels including permanent flooding (I1), irrigation with 8 days interval (I2), irrigation with 13 days interval (I3), irrigation with 18 days interval (I4) throughout the plant growth period and sub plots are application of organic manures including control (without fertilizer or manures), chemical fertilizers based on soil chemical properties results, 10 t/ha poultry manure, 20 t/ha cow manure and 40 t/ha sheep manure. Before the initial plowing operation, a compound sample from several points of farm soil prepared and sent to the Soil and Water Laboratory of the Rice Research Institute for chemical (nitrogen, phosphorus, potassium, organic matter, acidity) and physical (specific gravity) properties analysis. Field preparation operations have been carried out and rice seedlings would be transplanted with 20× 20 cm cultivation pattern. After transplanting, the plots will be kept flooding for 10 days to establish the seedlings. After that, irrigation management in main plots is applied according to the plan. Water is introduced into each plot by hose and the amount and depth of irrigation water (amount of water used) for each plot is measured by a meter. In order to prevent water leakage from one plot to the adjacent plot, the distance between the main plots is considered to be two meters and all borders will be covered with very thick plastic. Soil moisture is determined before irrigation and moisture changes in various experimental plots are measured during the growing period of the plant. After each rice cultivation period, soil sampling is prepared from all experimental plots from a depth of 0-25 cm above the soil surface. In order to measure the chemical (nitrogen, phosphorus, potassium, organic matter, acidity) and physical soil properties (specific gravity), samples will be sent to the soil and water laboratory of the Rice Research Institute. Agronomic traits such as plant height, number of tillers per plant, number of fertile tillers per plant, number of panicles per square meter, panicle length, total number of grain per panicle, filled grain number, grain yield, biological yield, harvest index and nutrient elements concentration (N, P, K) in grain and straw will be measured. Data analysis will be performed with SAS software (version 9.4) and means comparison will be done using LSD5%.