The environnemental quality of soil under wheat and vinesin the region of Mohammadia Benslimane (Morocco)

This work aims to assessing the environmental quality of agricultural soils under vine and wheat cultivation in the area of Mohammadia-Benslimane (Morocco). 80 soil samples were collected and studied. The results have been studied and recorded on the agronomic parameters; show that the soil’s textures contain clay andthe values of pH are neutral to slightly acid in all stations. The electrical conductivity values are clearly higher in soils under wheat than in those under vine. The CaCO3 contents within the different studied soils are generally similar in all stations. Moreover, the organic substance rate seems to be more important in the soils under the wheat crops (2%) than in those under the vine crops (1, 7%). For the four analyzed elements: Cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn), the lead and the zinc present a high concentration in the vine yard Plots compared to those of the wheat. The concentrations of the Cadmium in a few stations exceed the standards (2 ppm) and can reach 10,37 ppm. The order of the average’s contents with the lead and the zinc are 20,12 ppm and 148,60 ppm, respectively. They are inadequate with the concentration standards for a normal soil, ie 100 ppm for pb and 300 ppm for zinc. As regards metallic pollution, its index increases, for the soil under the vine (it takes the values from 0.281 to 2.203).


Introduction:
The contaminations of soils with the heavy metals have become one of the major environmental problems around the world [1,2,3,4].It becomes a source of danger to the health of people, even to those living in the cities [5,6,7]. The anthropogenic pollution iscaused by the heavy industries which in the enters plants, then it goes through the food chain and ultimately endangers the human health [8,9,10,11,12]. In addition, by the wind, the top layer of the soil can be easily resuspended, as a dust particle and it can be inhaled. It is well known that the toxic elements tend to accumulate in the smallest particle size fractions of the soils [13]. The most common heavy metals found at contaminated sites, in order of abundance are Pb, Cr, As, Zn, Cd, Cu, and Hg [14].The heavy metals such as Cd and Pb havecarcinogenic effects [15,16].
Other metals such acopper and zinc are essential nutrients for the human health, but they can be toxic at high concentrations [3]. For example, Zn can reduce the immune function and the levels of high-density lipoproteins [17]. It is also found that, Cu can cause an acute stomach, intestine aches and liver damage [18].Research on soil quality in Morocco is a topical issue and it is a part of the sustainable development policy envisaged by the national authorities, particularly, in its new agricultural policy "Green Morocco Plan".On a contemporary map of key wine producing areas around the world. Morocco and its North African neighbours would hold a less than prominent position. Recently, in Morocco, it is estimated the size of vineyards specifically for wine grapes:10000 hectares, it dwarfed by both major European and New World producers alike Morocco is however a country with potential for quality winemaking, even the prominent religious and political difficulties. The country is still coming to terms with its colonial past and it is this legacy which continues to influence wine-making within Morocco as significantly now as it has done for the last hundred years.The first cultivated grapes were probably introduced to Morocco by Phoenicians and Carthaginians [19,20]. Those introductions, and their putative derivatives resulting from hybridization among cultivated and wild forms, could represent the oldest cultivated vines in the region, truly commercial viticulture was introduced to the country in the early twentieth century with the arrival of French colonists in 1912 [21]. Under their efforts land under vineyard swelled to 50000 hectares by the midtwentieth century with traditional southern French varieties including Carignan and Cinsault making up the majority of plantings.
The evolution of areas occupied by vine growing over the last 20 years has been characterized by a decline in both types of vineyard land in favor of cereals. The Moroccan vineyard covers a total area of 50 000 ha in 2006 and 2011 viticulture occupied an area of 48 000 ha [22]. With an area of cultivation of 44 600 ha in 2017, grapevines rank fourth among fruit crops of Morocco and represent one of the most valuable crops for the country's economy [23].
In the region of Mohammedia Benslimane (Morocco), we found that vineyards have declined in favor of wheat growing. The evolution of areas occupied by vine growing over the last 20 years has been characterized by a decline in both types of vineyard land in favor of cereals.This change in rotation would have an impact on the quality of the soil in this region [24]. The aims of this study are to identify the soil characteristics in the agricultural soils under the vine and the wheat in the region of Mohammadia Benslimane (Morocco)and estimate the trace element in the soil under the vine and the wheat. In addition, analyzingthe pollution index and the correlation between the organic parameters and heavy metals.

Materials and methods
The area of this study belongs to the provinces of Mohammadia and Benslimane cities located on the Atlantic coast of Morocco (figure 1).This area is located between the cities of Rabat and Casablanca,This region is characterized by a semi-aridMediterranean climate. The annual rainfall average of the last 20 years is 400 mm. The oceanic influence creates a variation at the level of the forest microclimate [25].Throughout this work, 8stations within the region of Mohammadia Benslimane are our main field of study. We have examined 10 samples in each station in the horizon [0-20 cm]: (5 samples under the cultivation of the wheat and the other ones under the vine). After transportation to the laboratory, the soil sampling was air-dried and sieved through <2 mm mesh. Subsamples were used to measure the physical-chemical properties according to the standard procedures.
The analysis of the texture in the various stations is determined by the Robinson pipette method [26]and the analysis of the organic matter has been conducted using [27]method.The electrical conductivity in the method of [28], the soil pH was measured with H 2 O (1:2.5 ratio) method of [29]while the dosing of CaCO 3 was made by the method of Bernard [30].
Concerning the heavy metal concentrations, the soil was extracted by aqua regia at 160 -C. Then the metal concentrations in the digests were determined by the inductively coupled plasma-optical emission spectrometry.  The pH is considered as the main chemical parameter controlling the bioavailability of the heavy metals in the soil [31].
The pH results in this study show that, the values are neutral to slightly acid in allstations. The values of the pH measurements arerecorded in the soils under the wheat cultivation are higher in comparison with the soils under the vine cultivation with the exception of Fdalate (figure 3).

Soil pollution in Cd, Cu, Pb and Zn
The concentration of the metal trace elements (MTE) which is measured in the soil is the outcome of the heritage created by alteration of the rock concentrations (local geochemical background), more or less altered by soil formation process (soil geochemical background). This background is enhanced by the contributions of the human activities [32].   [33,34,35,36,37]and this is the case of our soils. Cereal crops are considered by several authors quite insensitive to iron deficiency and this is the case of our soils. Cereal crops are considered by several authors quite insensitive to iron deficiency [38]. On the other hand, the vine is more sensitive, the ferric chlorosis mainly affects the young plantations of two to three years [39]. . From neutral to slightly acidic pH, Cd is less mobile because of its high affinity with organic matter and soil nutrients (NPK) [41,42,43,44]. This could explain the high Cd concentrations that are probably due to the inputs of manure and phosphate fertilizers rich in Cd. In addition, the Cd affinity for CaCO 3 was confirmed in the different works of [41]. The copper can cause phytotoxicity in vine-planted soils that have been treated with copper salt, which has been used as a fungicide for many years. Then it induces ferric chlorosis and decrease Fe absorption. The vine does not suffer because its root system mainly explores the soil in  This result explained by the fact thatPb is not very mobile,since it is mainly associated with the clays and the organic matter, it is mobile only when it forms soluble organic complexes and / or when the soil has exceeded its absorption capacity for Pb [46,47,48].
We have given in figure 11 the lead levels which are found in the other stations.it is see that the concentration of lead do not exceed the value 67.14 ppm.The difference in lead concentrations between the vineyard and the wheat plots is highly significant for all stations.Thus, the maximum concentration of lead is recorded in soils under the vineyardswhich are treated in the traditional way (from 40.84 to 67.14 ppm), while the areas of Mansouria and Bouznika show a low level of lead with an average varying from 38.36 to 40.84 ppm. The difference in lead concentrations between plots of the vine and the wheat is highly significant in all stations. The Zinc substance which is an essential element for low dose. However, it causes an acute toxicity with a high dose [49]. The zinc, which is also an essential low-grade element, causes acute high-dose toxicity.
In our study, the average concentrations in the vineyard soils are higher than those in the wheat soils in all stations. The difference in zinc concentrations between vineyard and the wheat plots is highly significant in the Mansouria, Cherrate,Skhairate,Zniber and Fdalateareas.  Figure 12).This decrease can be explained by the solubility and mobility of this soluble element relative to the other heavy studiedmetals.

Pollution index
The heavy metal contamination on the environmental surface is associated with all contaminants rather than just one metal. Several au thors have introduced the soil pollution index to identify the multi-element contamination that results from an increase in the metal toxicity [50,51,52].The pollution index is defined as the average ratio of the metal concentrations in the soil samples to the limit values [53].  (Figure 13).
We have found in all stations that the pollution index is higher in soils under the vines than the soils under the wheat. Thepollution indexes clearly increase in thestations of Zniber and Fdalate.These trends can be explained by the location of those three situationswhich isnear the roador the treatment with phosphate fertilizers rich in Cd and the pedo-geo-chemical background of these stations.

Conclusion
For the agronomic characterization of the studied soils,we canconclude that the electrical conductivity, the pH and the organic matterhave a high value in the soils under the wheat compared tothose of the soils under the vines. This tendency can be in one part, influenced by the residue nature of the agriculture contribution to soil and in another part;it can be influenced by thefarm manure contribution.