تأثير أسلوب إدارة الارض في حالة بعض العناصر الصغرى وصفات الترب المزروعة بالرز جنوب العراق

Abstract

This study was carried out to investigate the effect of long-term agriculture with the monoculture system of rice crop and the crop rotation- م system of rice-wheat, compared to non cultivated soil, in physical and chemical as well as soil fertility properties, represented with soil content of total and available formula of iron, manganese, zinc, copper and Silicon.And to determine the status of the formation and genesis of these soils after a long period of use. We selected study transect which passes through the rice region from the north to the south, including three sites for study which are: Abbasiyah, Al-Shamiya and Mashkhab districts within the provinces of Najaf and Qadisiyah. At each site, we selected three representative isolates of agricultural systems above. The pedons were revealed fundamental according to the Soil Survey Staff division (1993). Soil samples were collected from each horizon for the required measurements and analysis, addition to undisturbed samples were also taken for the purposes of the micro morphological studies. During the phase of sacking of rice plants in 2017 and 2018. Plant samples were randomly obtained at each site used in both agricultural systems at the three study sites, as well as samples of irrigation water used in the area for irrigation. The plant samples were dried and divided into three parts: roots, stems+ leaves and ears, and the concentration of nutrient concentrations above were determined. Irrigation water chemical properties which were required to classify its quality are estimated according to the US laboratory for water classification. The results of the morphological description indicated a difference in some morphological characteristics, especially the structure, texture, soil depth and horizons continuity, while there was a clear variation in color as well as in the mottling status due to oxidation and reduction process activity in the soil used in rice cultivation, which was reflected in soil color. The values of the clay seperat ranged from 101-395 g.Kg-1 , sand 56-512 g.Kg-1 and silt 325-837 g.Kg-1 . The soil texture in the three study area was within the medium to fine classes, the results also showed that there was a difference in the bulk density values of the study soil, it was ranging from 1.31 - 1.78 Mg.m -3 , the highest values for this parameter were recorded in the pedons which used in the crop rotation system compared to the monoculture system, with a significant increase in soil resistance for penetration values, reached 18.3% compared to non-cultivated lands soil.. There was also a significant increase in the weighted diameters rate when the land cultivated. It was increased from 0.08 mm in the non cultivated soils to 2.01 mm and 2.15 mm in the monocultural and crop rotation farming systems. The results of soil chemical analysis indicated that the values of electrical conductivity ranged from 1.0 to 26.5 dS.m-1 with a significantly decrease in the saline content in the soils cultivated with rice crop, while its rised in non cultivated soils. The values of soil reaction ranged between 7.6-8.3 its showed increasing in this parameter in cultivated soils compared to not cultivated soils, due to the effect of ن immersion processes which associated with rice cultivation. As for the soil content of the organic matter, the soils in cultivated pedons was recorded higher values incompletion to not cultivated soil, the soil content from this component ranged between 0-30g.Kg-1 soil. Carbonate equivalent values ranged from 210-371 g.Kg-1 and not cultivated soils showed higher weighted average values of this characteristic compared to the cultured soil used in both farming systems, the values of the exchange capacity of cat ions in soil ranged from 22.9- 10.6 cent mol. charge Kg-1 . The results of the complete element analysis showed that the values of sesquaoxide, Al2O3, Fe2O3, and SiO4 were higher in cultivated soils compared to not cultivated soils, the results also showed a clear rise in the easy moved elements MgO and CaO in the not cultivated soils but there are decreased in the cultivated soils. The results of the micro morphological characteristics confirmed that there is a difference in the degree of development of the cultivated field soils through the presence of some micro-morphological manifestations, such as Clay Body, Argillans, Ferri-argillans, Orgiargillans and Calcians, which was confirmed the movement of soil components from top to bottom, as for not cultivated soils a secondary carbonates sedimentation was observed in the pores. The development of cultured soils under the conditions of rice cultivation has confirmed the results of the clay accumulation index, the physical index and the pidogenical index, as well as the profile darkness index. The total content of iron in the study soil was ranged between 24.0-58.3 g.Kg-1 with average 37.4 g.Kg-1 , the total manganese ranged between 265-875 mg.Kg-1 with average 469.3 mg.Kg-1 , while the total zinc ranged from 35-65 mg.Kg-1 with average 51.2 mg.Kg-1 , while the total copper ranged from 37 to 20 mg. Kg-1 at average 29.4 mg. Kg-1 ,finally total silicon was ringed between 20.5-12.6% with average 16.1%. The agricultural system and land use has a significant effect on reducing the total content of these nutrients in the soil. The results of the chemical analyzes for above nutrients available formula in the study soil showed a significant increase in the cultivated soils and in both farming systems compared to the not cultivated soils. The mean of available iron ranged from 8.7-9.2 mg.Kg-1 in cultivated soils compared to 7.8 mg. Kg-1 in the not cultivated soils, while the available manganese was ranged between 2.8- 36.2 mg.Kg-1 with mean 21.5 mg.Kg 1,while the ratio of available zinc in the study soils was 1.3 mg.Kg-1 In not cultivated soils increased to 2.0 mg.Kg-1 in cultivated land which used by both farming systems. While available copper content in the study soils was ranged between 0.9-2.0 mg.Kg-1 , as for the silicon component, the soil content of available formula was ranged between 29.0-40.1mg. Kg -1 at the average 30.0 mg.Kg -1 , with a significant increase in soil content from this element availability when the land was cultivated. The increase in nutrient availability in soil has been positively and significantly reflected in ه concentrations of these nutrients in rice plant parts (roots, stalks + leaves and ears) at the expulsion of the ears stage in all study areas. The chemical analysis of the irrigation water in the study areas showed that it was water of class C3 (high salinity dS.m-1 2.25-0.75) and the ratio of sodium adsorption in the excellent class S1(less than 10 mol.charge.m3 ) 1/2 according to American salinity laboratory classification. The morphological, physical and chemical results in the not cultivated soils indicated the predominance of the calcification process, while reduction activity was observed as well as the predominance of loss and gain processes, especially for the clay separate and carbonate in the cultivated pedons under both farming systems. All studied soils was classified within Aridisols order and was subdivided into Calcids and Argids suborder level, while in terms great soil groups there were within Haplocalcids in the Shami area when they were cultivated with both farming systems transformed to Calciargids, the soil of the Mashkhab site has been transformed from Haploargids in not cultivated soils to Calciargids because of the conditions associated with growing the rice crop, while all soils of the Abbasiyah region was within Haplargids and regardless of agricultural land use or not. The diagnosed sub great groups within the studied regions were Typic Haplocalcids and Typic Haploargids which found in not cultivated soils at Shamiya , Abbasid and Mashhab sites respectively. While Aquic Haploargids were present at the site of Abbasia when its cultivated, the Aquic Caciargids sub great groups was diagnosed at the site of Shami and Mkhakab when there was cultivated, due to the wetting conditions which pass through these soils due to the cultivation of rice during some times of the year, while the diagnosed soil series were 133CCP and 132CCP and 123CCP at the Abbasid, Shamiya and Mashaq sites respectively.