ASSESSMENT OF SOIL QUALITY AND HEALTH USING SOME PHYSICAL AND BIOLOGICAL PROPERTIES FOR FADAK FARM PROJECT

Fadak farm project was selected to conduct this study and to evaluate the state of quality and health indices in term of soil physical and biological properties, where this farm is located in Holly Najaf Governorate. Some physical properties (soil texture, mean weight diameter, bulk density, porosity, infiltration rate, saturated hydraulic conductivity and available water) were selected to assess the quality then health indices, and the biological characteristics (vegetation coverage, soil respiration, bacterial and fungal counts) were also selected to assess the quality and health indices in term of these properties. Results showed that classes of moderate and poor soil health were dominated in lands of this farm for each physical and biological properties. It was noted that the class good of soil health was collaterally appeared in small areas according to biological characteristics


INTRODUCTION
Soil health is defined as the continuous capability of the soil to function as a living biological ecosystem that preserves humans, animals and plants, and it is a combination of the physical, chemical and biological properties of the soil that can easily change depending on environmental conditions and changes (8,44).Soil quality and soil health are the two terms used to describe the functional state of soil.They describe the capability of soil to maintain crop productivity, environmental quality, and support plant, animal, and human health.The term "soil biological health" can be used to refer to the biological function of soil in relation to plant growth, yield and productivity (45).The use of the term "soil health" emphasizes that a soil ecosystem requires maintenance and conservation to maintain the biodiversity and biological activity.Karlen (34) stated that the concept of soil health has evolved over the past several decades and they emphasized the need to advance scientifically in monitoring and evaluation protocols through (a) improving indicators recording tools (b) developing national monitoring protocols (c) identifying new soil biological, physical indicators of soil health.They also emphasized that producers' interest in soil health monitoring and region-appropriate interpretation remains strong.To meet these needs, the USDA-Norwegian Red Cross and USDA have initiated the Cascade Analysis Project that focuses on the interpretation of indicators and the development of tools.Healthy soils are critical to the health of ecosystems, economies and populations.Hence, it is widely recognized that soil health is important for quantification, both for assessment and as a tool to help guide management strategies.What is less clear is how soil health is actually measured, especially given that soil health is not exclusively a product of soil physical and chemical properties.Because of their wellestablished importance to many aspects of soil health, microbiology and bioactivity are often used as measures of soil health with a range of different biota-based measures routinely found around the world (18).The current study aims to: Assessment of the health of the soil units of the Fadak farm project by adopting health evidence.Also, indication of the effect of variability in vegetation overland cover and use type in the variance of biophysical quality indices for the study area.And to diagnose the condition and degree of deterioration in the soil units of the region and develop administrative solutions for them.

MATERIALS AND METHODS study area:
The Fadak farm project was chosen in the governorate of Najaf.The project is located in the northwestern side of the governorate of Najaf, within the coordinates 40600 to 418000 North and 3537000 to 3545000 East.The total area of the project is estimated at 35943 ha Figure 1 shows a map of Iraq on which the project site is located.Investigations and Land Classification of the Ministry of Water Resources in preparation were used for field visits.As well as used later in the production maps of soil characteristics under the GIS environment using ArcGIS 10.3.Field methodology: Before starting sampling, the study area was visited to determine the locations of pedons as well as to determine the locations of the surface samples.It was taken into consideration while defining the paths and the study plots that they cover most of the project lands and in different directions.As 40 random surface samples representing the farm were taken from a depth of 0-0.3 m using the auger drilling machine.Eight pedons representing the soil of the study area were excavated and its horizons were described in a fundamental morphological description according to the Soil Survey Staff (46).laboratory procedures Soil samples were dried and divided into two parts, the first was left without grinding or sieving in order to measure mean weight diameter, while the soil samples for the second part were ground and passed through a sieve with 2 mm openings in diameter and the necessary measurements were taken on it.physical properties particle size distribution was determined according to the method given in (43).Soil bulk density was estimated using the core method according to the Blake and Hartge method described in (37).Porosity was calculated through the mathematical relationship between both the bulk and particle density as stated by (23) and according to the following equation.
=  ∆ () Since: K: Saturated hydraulic conductivity V: Infiltrated water volume (cm³), L: Soil Column Length (cm), A: flow-section area (cm²), t: Water collection time (hour), ∆H:The change in water potential between its entry and exit point Soil resistance to penetration: use a pocket penetrator pocket penetrometer CL 700 has a cylindrical stem and flat end with a diameter of 0.672 cm and a penetration depth of 1 cm from the surface to measure soil penetration resistance was measured according to the method proposed by (15).Mean weight diameter was determined using the method suggested by (52).Available water was calculated by the difference between volumetric moisture content at field capacity and permanent wilting point using pressure discs according to the method mentioned in (9).

Biological properties
Total soil bacterial and fungal counts: It were done according to the methods presented in (6).Soil respiration: Soil respiration was measured by the production of carbon dioxide gas using a carbon dioxide meter device according to the method presented in (21,24).Organic Carbon and Organic Matter: The percentage of organic matter was estimated after estimating the organic carbon and converting the values to the organic matter content in the soil by the wet oxidation method according to the Walkley Black method described by (33).Organic matter (%) = Total organic carbon (%) × 1.72 (3) vegetation coverage: Use the application Canopic to extract the value of the vegetation cover on the soil surface to isolates the green cover in a specific area from the rest of the covers and calculates the percentage of vegetation cover percentages, the program is a multi-purpose green cover measurement tool developed by Soil Physics Research Group (http:// soilphysics.okstate.edu/) and (https://appcenter.okstate.edu/)at Oklahoma State University.http://canopeoapp.comIndices of soil quality and health: The soil quality index was calculated by adopting the physical and biological characteristics, each separately, through the values of the measured properties, as well as the dual overlap of all the properties.The current study is for the purpose of calculating the soil quality and health indices for the mentioned properties, and then the dual overlap of the combined properties.=

SQI biological = (fungi x bacteria x vegetation
x CO 2 Soil respiration) 1/4 (5) Whereas: Fungi = number of fungal colonies, Bacteria = number of bacterial colonies, Vegetation = percentage of plant coverage, CO 2 soil respiration = soil respiration (carbon dioxide concentration).The following categories were used in assessing the degree of soil quality and health index: Soil quality and health index for all physical and biological characteristics SQI Total = (SQI physical x SQI biological) 1/2 (6) Whereas: SQI total = total soil health index, SQI physical = soil quality index for physical characteristics, SQI biological = soil quality index for biological characteristics.The physical and biological indicators were adopted for the purpose of assessing the quality and health of the soil in the current study according (48).

Particle size distribution
The results of the mechanical analysis of surface soil samples in the study area shown in the table (2) However, the textures of the soils that were studied were coarse and medium in general.It is noted that the sand content is high throughout the study area compared to the content of clay and silt, and the sand content ranged between 336-776 gkg -1 , while the clay content ranged between 260-152 g kg -1 , and the silt content between 64-424 gkg -1 .The reason for the high content of sand compared to the content of clay and silt is due to the nature of sedimentation taking place in the desert study area, where these soils are desert that originally originated from ancient marine sediments from the bottoms of the ancient sea of Tethys, which covered most of the study area, as well as the wind sediments that are common in which rough separation of separates (4,9,12).It is noted that the clay content showed the least spatial heterogeneity compared to the content of sand and silt, and the reason is due to the fact that most of the soil textures of the study area were within the textures of coarse and medium texture, where the content of sand separated in them increases compared to the fine separated, which is clay, which is reflected in the variation in the content of both, as well as About the emergence of more varieties as protomorphic units on the spatial distribution map due to the wide range of sand and silt content compared to the content of clay.The result of these medium textures led to the predominance of the cultivation of grain crops in the project area, especially wheat and barley as well as greenhouse agriculture.

bulk density
Table (1) shows the values of the bulk density of the study area in general, which ranged between 1.32 -1.51 Mg.m -3 .Although all samples of the study area were generally of coarse texture, the decrease in the value of the bulk density was due to the nature of the land use for that site, as a significant decrease in the value of the bulk density in the greenhouse agricultural areas and the fields of alfalfa and wheat due to the field management applications by adding organic matter (humus) and plant residues, which was positively reflected on the values of the bulk density, which led to a decrease in those values, while an increase in the values of the bulk density is noted in the areas of barren lands, not cultivated and reclaimed lands, and because of the predominance of coarse grained in it, the values of the bulk density increased (36,39).Total porosity: The total porosity values in the study area ranged between 0.43 -0.50 cm 3 cm -3 .it is noted that low values of porosity are associated with higher sand content, whereby an increase in the coarse separation leads to a decrease in the porosity, while the latter's values are lower than the high content of the fine sand (35,40).as it is noted that the porosity variety, which lies between 0.45-0.47cm 3 cm -3 is dominant, followed by the variety 0.43-0.45cm 3 cm -3 , while the variety with the range 0.47-0.5 cm 3 cm -3 was the least distributed in the study area, this was also affected by land uses in the study area, where the increase in porosity values was related to the content of fine separate on the one hand, and land use on the other.Mean weight diameter: Table (1) shows the values of the mean weight diameter of the study area, which ranged between 0.20 -0.373 mm.Although the texture of the area is coarse and medium coarse in general, a noticeable increase was observed in some areas of the farm, especially in the areas of palm and pomegranate cultivation, as well as greenhouses as well as the fields of alfalfa where this rise is attributed to the soil management practices and reclamation processes applied to those areas, including the addition of organic materials and improvers, which led to this rise in values compared to the rates of barley lands and unused lands of the farm so far.(16,38,44,45).Soil water infiltration: Table (1) shows that there are high differences in the values of the cumulative infiltration according to the type of cultivated vegetation, whose value ranged in 3600 seconds between 5.18 -17.34 cm h -1 , and that the lowest cumulative infiltration in the soil was under the cover of greenhouse cultivation, followed by the lands that were prepared for the cultivation of vegetables, while the highest value was recorded in the fallow and barren lands, and the reason is due to the accumulation of salts in some of the fallow lands, as well as the lack or of organic matter, which leads to a decrease in the soil holding capacity for water and consequently the high value of the infiltration as well as the main effect on the soil of the study area, where those resulted was also found (3,5,6,19,51).saturated hydraulic conductivity: Table (1) shows the values of the hydraulic conductivity of the soils of the study sites, where the results recorded the highest value of the saturated hydraulic conductivity was 3.24 cm min -1 in greenhouses cultivation areas, while the lowest value was recorded 0.566 cm.min -1 in the fallow and barren lands of the farm due to the texture class of the study area in general, its inability to hold or retain water, the lack of organic matter in the fallow lands, and the absence of soil conditioners, on the contrary, what is found in the cultivated lands.It is also noted that there is a clear trend in the correlation of the saturated water conductivity values with the infiltration rate, as with the increase of the latter, the saturated hydraulic conductivity values increase.(1,2,32,49).Resistance to root penetration: Table (1) shows that the values of soil penetration by roots ranged between 157.6-230.Kpa This rise is due to the formation of a hard surface crust in most areas of the farm, especially in the uncultivated lands.It is also noted from the table that the values decreased in the cultivated areas, the greenhouse cultivation areas and the areas of palm, pomegranate, pistachio and wild jujube trees because of the plowing and the breaking up of the soil and the surface crust, which led to a decrease in values of this property in these areas, in addition to the relatively high content of organic matter in the soil in those areas compared to the fallow areas, also soil texture plays a major role in the effect on the values of penetration resistance, where the values of the penetration resistance of the roots in the study area are relatively high due to the high content of sand in them compared to clay soils and soils with a high content of organic materials due to the effect of the sand content in increasing the friction when measuring this characteristic with the penetrometer (14,23,27).Available water: It is noted from Table (1) that the available water values ranged between 0.060-0.133cm 3cm -3 , where the values of the available water content were related to the soil texture.In the soils with loam and sandy clay loam textures, the values of the available water were higher than in sandy loam soils, due to the fact that the total pore size in soils with a higher clay content is much higher than soils with a higher content of coarse separates, although the diameter of the pores in coarsetextured soils is higher than that of finetextured soils, and this was confirmed by all references in soil physics and water sciences (11,28,29,30).Biological Characteristics: vegetative coverage: Table (2) shows the percentages of plant coverage for the study area, as this percentage reflects the situation of the area in general, whether it is exploited or not, as the coverage of the study areas ranged between 0-93%, where the values were recorded between 0-7 in completely fallow lands and lands where some predominated by natural plants spread within the sampling area, while the values that ranged between 15.60-93 were in the rest of the cultivated study areas, starting with the fields of pistachio, wild jujube, palm and pomegranate bushes, up to the greenhouses and alfalfa fields that took the highest values.Where the cultivar with vegetation coverage prevailed in the region 0-25% of the total area, which represents most of the abandoned areas and some areas of modern cultivation of pistachio and wild jujube bushes, followed by the cultivar 50-75% of dominance, which is represented by areas of cultivation of grain crops for the current season and the residuals of the previous season after harvesting as management systems were followed in the crop residues after harvest to improve the properties of the soil in general, as well as some areas of palm trees and some other fruit trees.Soil respiration (concentrationCO 2 ): Table (2) shows the values measured by a carbon dioxide meter (CDM) device for the farm areas, which ranged between 215-847 ppm at a temperature of 30°C, as these values differed according to the type of vegetation and the type of plant grown for each of the farm regions.When the cultivated areas in general recorded higher values, ranging between 386-847 ppm, and the difference in this respiration rate was due to the type of planted crops and the density of the plants in the same measured area, as it gave the highest value in the alfalfa field.In the roots of the plant and its proximity to the surface layer of the soil, as well as the high density of the planted alfalfa plant, followed by the protected cultivation areas, which recorded different values ranging between 728-793 ppm, depending on the different type of planted in the greenhouses, as well as the percentage of adding organic matter and humus.It is noted from the results that the predominance of the class 215-400 ppm, which is the weakest in the study area, and the reason is due, as we mentioned earlier, to the nature of the land uses.Bacterial numbers: Table (2) shows the values of soil content of bacterial numbers, as it ranged between 4 × 10 5 -31 × 10 8 colonies cfu g -1 soil.It is noted that there is a wide range of bacterial colonization values in the soil of the study area, and the reason is certainly due to the nature of the land uses in each area, as low values of bacterial density were found in the abandoned areas and some areas with little vegetative coverage, while high values of bacterial density spread in the areas of highly used, especially in the areas of cultivar and grain crops, and the reason is may due to the increase in the activity of microorganisms in the root zone of those areas.(13,17,50).Fungi communities: Table (2) shows the values of the soil content of the fungal numbers, which ranged between 2×10 3 -22×10 3 cfu g -1 , which are less than those found on the surface of fertile soil, that amount to 4×10 5 cfu g -1 .This decrease may due to the drought and lack of nutrients in desert soils.These small values also varied in their spread over the area of the study area according to the land use of each region, as the values of fungal density increased proportionately in the greenhouse lands and the alfalfa fields, where the number of fungi in those lands reached 22 ×10 3 and 20 ×10 3 cfu g -1 respectively, while the highest value was recorded in unused and fallow lands at 6.5 × 10 3 cfu g -1 .The reason for this increase is due to the management practices used on the cultivated lands to provide a moist environment and the addition of organic materials, which led to a clear increase in the number of fungi in these areas.

Soil quality and health indices:
The soil quality index known as SQI is a set of properties that provide numerical data related to the ability of soil to perform one or more functions, while soil health is an assessment of how well the soil performs all of its functions currently and how these functions are maintained for future use (31,46,47).The soil quality index for the Fadak farm project in Najaf Governorate was measured by adopting a set of physical properties to set up the SQI.Soil quality and health index in relation to physical properties: The soil quality index was measured for the physical characteristics, as the soil texture, bulk density, porosity, weighted diameter rate, infiltration, saturated water conductivity, soil penetration, and ready water were selected by adopting the limits of field capacity and permanent wilting point.Table (3) shows the values of the soil quality and health indices for the physical properties, as these values ranged between the first and second classes, while the third class did not appear among those classes, due to the fact that the study area is desert in which coarsetextured soils are common, which affects the rest of the physical and hydraulic characteristics of the soil such as the bulk density, porosity and hydraulic properties of soil, which was reflected on the types of soil health in the performance of its functions, as the percentage of the poor type from the total area of the project reached (12%), while it reached The percentage of the moderate variety (88%) of the total area of the project (figure 2), while the good variety did not appear as a soil health class because the study area was affected by its arid conditions, and the high sand content in most of the soil textures of the study had a strong impact on other physical characteristics, especially hydraulic This also confirmed by (20,22) that the increase in sand content increases both the tip rate and the saturated and unsaturated water conductivity, as well as the increase in the values of bulk density and a clear decrease in the stability of the assemblies.

Figure 2. physical soil health class Soil health and quality indices for biological characteristics:
The soil health index was measured for biological characteristics, as the characteristics of vegetation cover, preparation of microorganisms, soil respiration, vegetation cover, and biomass were selected.Table (3) shows the values of the soil quality and health indices for the biological characteristics, as these values ranged between the first and second classes at a higher rate than the third class, due to the prevalence of arid conditions in the study area that affect the growth of organisms in general and affect the growth of microorganisms in particular.This is reflected in the varieties of soil health in the performance of its vital functions.Table (3) shows the emergence of three types of soil health in relation to the biological characteristics, the poor and moderate types were prevalent in the study area, as the percentage of the poor type of the total area of the project was (44%), while the percentage of the moderate variety reached (53%) of the total area for the project, the percentage of the good class was (3%) of the total area of the project (Figure 3).

Figure 3. biological soil health class
After estimating the physical and biological characteristics of the soil and extracting the types of soil quality and health, all the traits were adopted in extracting the type of quality index and their validity in relation to the aforementioned properties combined, as the soil characteristics actually affect in an overlapping manner with each other, as the physical characteristics such as soil texture and apparent density affect the vital characteristics Clearly.Table (3) shows the types of soil quality in relation to the physical and biological characteristics combined with each other, as it is noted that the first and second types appear in common with the emergence of the third type in only two locations, and this is reflected in the soil health types that ranged between poor and moderate.The appearance of poor and moderate classes in a common way indicates the possibility of modifying these varieties to the good classes after preparing an approved management plan in the management of desert soils using the available means of soil management in the service of soil and plants, and since the main factor in soils in arid areas is the abundance of water, so the provision of water suitable for irrigation and the addition of enhancement reagents, as well as the cultivation of some hybrids tolerant of salinity, heat and drought, is one of the means of sustainability in the uses of desert soils.Conclusions: From the previous results, the following can be concluded: The study area (Fadak farm) was characterized by the predominance of course and medium textures between sandy and mixed textures, with the emergence of some areas with sandy and clayey textures.The values of bulk density increased in the study area due to the high soil content of the separated sand as well as the low organic matter content in it.This was also reflected in the values of total porosity in the soil, which appeared at relatively low values in coarse-textured soils compared to mediumtextured soils.The values of the mean weight diameter reflected low values, which indicates the weakness of the soil structure and the stability of the aggregation in the soils of the Fadak farm project.The values of soil infiltration rate increased in the study area due to the high content of coarse separated in its soil.This was also reflected in the saturated hydraulic conductivity values.The values of the penetration resistance of the roots showed relatively high values due to the high content of the coarse part.The effect of the sum of the physical and hydraulic properties of the soil on the limits of the field capacity and the permanent wilting point and consequently the content of ready water in the soil.Because of the difference in land use in the Fadak farm area, the vegetation coverage showed varying levels from one region to another, depending on the nature of the land use in each location.Also, the characteristic of soil respiration differed after measuring the concentration of carbon dioxide in the soil air according to the nature of the land use in it.Microbial communities (bacteria and fungi) showed low values throughout the study area, with a good content in the soils of the areas cultivated with jet and protected agriculture.The soil quality index for physical characteristics showed two types of soil quality, they are the first and second types, which correspond to the poor and moderate types in the approved soil health classification, where the moderate variety was dominant.Likewise, the case appeared in the classification of the soil quality index with regard to the chemical characteristics.Soils fell into two types of soil quality, the first and the second, which corresponded to the poor and moderate types in soil health, and the moderate type prevailed in it.Small areas showed good qualitative evidence for the vital traits with the emergence of the poor and moderate classes in these traits, as the dominance was also located for the second class in the quality index and the moderate class in its validity.In the overall physical and biological characteristics, the soil quality index showed two types prevalent in the study area, the first and second types.

Figure 1 .
Figure 1.location map of Fadak farm Office methodology: Prepared maps by the National Center for Water Resources of the Research and Design Department / Division of Hydrological Investigations and Land Classification of the Ministry of Water Resources in preparation were used for field visits.As well as used later in the production maps of soil characteristics under the GIS environment using ArcGIS 10.3.Field methodology: Before starting sampling, the study area was visited to determine the locations of pedons as well as to determine the locations of the surface samples.It was taken into consideration while defining the paths and the study plots that they cover most of the project lands and in different directions.As 40 random surface samples representing the farm were taken from a depth of 0-0.3 m using the