Journal of Earth Science & Climatic Change
Open Access

Egypt is dependent on imports of potash fertilizers to meet its annual requirements. In order to reduce the dependence on imported potash fertilizers, Glauconite (à potash mineral) has been identified as an indigenous alternative source of potash [1]. Glauconite is a naturally occurring mineral mined from ocean sedimentary rock known as “greensand”. It is often an olive-green colored sandstone rock found in layers in many sedimentary rock formations. The major chemical description of glauconite is ((K, Na)(Fe⁺³, Al, Mg)₂(Si, Al)₄O₁₀(OH)₂). Greensand deposits are found all over the world. The pH of the glauconite varies from slightly acidic to slightly alkaline depending on the source and has little effect of soils [2]. Glauconite is the name given to a group of naturally occurring iron potassium phyllosilicat mineral (mica group), green in color, very low weathering resistance and very friable composed of pellets or grains [3].

In Egypt, according to the thickness of the overlying glauconite sediments varies from up to 25 m in the Western and Eastern Wadis areas to less than 1 m in the high central area, El-Gideda mine of Bahria Oasis [4]. Glauconites occur in the Western Desert associated with phosphorites and iron ores [1]. Bambalov and Sokolov suggested that the glauconite is an improving agent for accelerated cultivation of soils with low fertility and damage in Belarus, United Arab Emirates and Egypt. Petkova et al., Pishmanov and Petkova reported that Lucerne and Wheat can be grown on glauconite-phosphorite substrate without any addition of mineral fertilizers. Many agronomic studies discussed the potential of glauconite as soil additive that gradually release potassium essential for plant growth [5-12]. Glauconite ores can be used instead of K₂SO₄ fertilizer and a base of ecological agriculture because they are not only an alternative of mineral fertilizers but they also can increase soil fertility [13]. The main objective of the present study was to evaluate the impact of the glauconite on growth and water use by corn plants.

Soil

The soil used in this study was sandy loam in texture and was collected from the newly reclaimed desert land at the Western district of the Nile Valley, West of Samalout, El-Minia Governorate, Egypt. Some analytical data of the studied soil are given in Table 1.

Table 1: Some analytical data of the studied soil.

Glauconite deposits

The tested fine glauconite in the current study was collected from Al-Bahria Oasis, New Valley governorate, Egypt and thoroughly mixed. A representative sample was taken and analyzed for the particle size distribution, pH, EC, P, K, Fe, Mn, Zn and Cu. Some analytical data of the tested glauconite are presented in Table 2.

Table 2: Some analytical data of the tested fine glauconite.

Set up of the pot experiment

The fine glauconite. was applied to the sandy soil at seven rates {0, 5, 10, 15, 20, and 25 Mgha^-1, as well as (0+375 kg K₂SO₄.ha^-1) for the comparison}. Each treatment was replicated 3 times. Three kg of the air dried treated soil were placed in a plastic pot (14 cm diameter and 20 cm depth). Five grains of corn (Zea mayz) were planted in each pot on 26 July 2014. The corn plants in each pot were thinned and fertilized with N and P at the equivalent rates of 250 kg N and 155 kg P₂O₅.ha^-1.

The corn plants were irrigated whenever required every seven days with an amount of water to compensate the loss in moisture which was maintained at the field capacity. At 60 days from the corn planting, the plant height (cm) and water consumptive use by the corn plants (l/pot) were recorded. The corn plants were cut at 2 cm from the soil surface and the fresh weight of the corn shoots (g/pot) was dried at 65°C and the dry weight of the corn shoots (g/pot) was recorded by weighing. Also, the water use efficiency by the corn plants was calculated. The oven dried corn shoots were grinded in a plant mill, passed through a 0.5 mm screen mesh, and a representative sample was taken and analyzed for the total nitrogen, total phosphorus, and total potassium. Analyses of soil, glauconite, and plant tissues were determined according to the standard methods [14-16]. All recorded data were subjected to statistical analysis of variance procedures. Treatments means were compared using the L.S.D. according to Gomez and Gomez in 1984.

Effect of applying fine glauconite (FG) to the sandy soil on some vegetative growth parameters and water use by corn plants

Data given in Table 3 reveal that, treating the sandy soil with different application rates of FG generally increased the vegetative growth parameters i.e., plant height, fresh and dry weights of corn plant, compared with the untreated control. The increase in almost all the studied plant growth parameters was proportional to the increase in the application rate of FG up to 15 Mgha^-1. However, the plants treated with FG at 20 up to 25 Mgha^-1, showed a decrease in terms of their vegetative growth parameters. It appears from the abovementioned results that, application of FG to the sandy soil improved the corn vegetative growth parameters, suggesting the proper increase in the grain and stover yield.

Table 3: Effect of fine glauconite on some vegetative growth parameters and water use by corn plants*.

The improvement in growth parameters of corn plants grown in the treated soil with FG may be attributed to the change in soil structure and water regime subsequently, water available to plants was increased also, to the effect of FG as a source of nutrients (Table 2) and that reflected on enhancing soil fertility. However, the decrease in growth parameters of corn plants at 20 or 25 Mgha^-1 rates, compared to 15 Mgha^-1may be attributed to the negative effect of salts that added to soil with these higher rates of application (EC=17.06 dSm^-1 for FG). It is clearly shown from Table 3 that the amount of water consumed by the corn plants grown in the FG treated soil were slightly affected, compared with the untreated control. On the other hand, as the water use efficiency refer to the amount of dry plant materials produced by each unit of water, and as the dry matter yield of the corn shoots grown in the treated soil with FG was much higher than the untreated one (Table 3), it could be seen that the water use efficiency was also increased. The highest value of the water use efficiency by the corn plants (1.87 g/L) was obtained with FG application rate of 15 Mgha^-1. compared with (1.39 g/L) with the control. The increase in water use efficiency due to treating with FG could be attributed to the effect of FG on increasing soil water holding capacity and decreasing water evaporation from soil surface, hence, increasing water available f or plants. The increase in water available with improving soil structure helped in improving the plant environment and subsequently producing more plant materials. The improvement in water use efficiency by corn plants implies that application of the tested FG to the sandy soil can rationalize the irrigation water required for growth. Similar observations were corroborated by a number of workers e.g. Prokoshev et al., Mazumder et al., Rao et al., Petkova et al., Akhtar and Jenkinsm, Eid and Morsy.

Nitrogen, phosphorus and potassium concentration and uptake by corn plants grown in the sandy soil

The effectiveness of glauconite as a source of K was assessed by determining the K content and uptake by plants. Data dealing with the effect of the tested FG on concentration and uptake of N, P, and K by corn plants are presented in (Table 4). Careful examination of the data presented in (Table 4) show that the concentration of N in corn shoots was decreased due to the application of FG. The concentration of P displayed no effect, while the K concentration was increased compared to the untreated control. The decrease in N concentration may be due to the dilution effect, as the dry matter was increased with no accompanied increase on N content in soil. The increase in K concentration may be due to the high K content of the added FG (Available K=846 ppm). The highest values of K concentration in the corn plants (3.7%) were obtained when 10 of FG was applied to soil. As can be seen from Table 4, increasing FG rate from 0 to 15 Mgha^-1 increased N and P uptake by corn plants, compared to the untreated soil. By contrast, as the tested FG rate increased from 15 to 25 Mgha^-1, the N and P uptake were gradually decreased. However, K uptake was increased with increasing FG up to 25 Mgha^-1. The increase in N, P, and K uptake by the corn plants could be attributed to the increase in nutrients concentration in soil by glauconite application.

Table 4: Effect of using fine glauconite on some nutrient’s concentration and uptake in corn plants*.

Generally, the increase in nutrients uptake may be due to one or more of the following reasons:

1. Presence of high amount of P and K nutrients in soil treated with FG compared with the untreated soil (Tables 1 and 2). This demonstrates that glauconite treatments could provide sufficient K for plants.

2. Plants grown in treated soil gave higher dry weight compared with plants grown in the untreated soil (Table 3).

3. The increase in ion mobility due to the increase in the available water in the studied treated soil.

4. Improvements in soil structure which reflected in increasing water holding capacity and decreasing nutrients losses by leaching.

The comparison between using FG and the recommended amount of K as seen in Tables 3 and 4 indicate that application of FG at the application rate of 15 Mgha^-1 was more beneficial in enhancing plant growth and water use efficiency than the treatment with the recommended K fertilizer. The same trend was true with the uptake of the tested nutrients, except K. Positive response in plant growth parameters with the increase in the FG application rate, it is expected that uptake of N and P must follow the same trend. The recorded improvements in plant growth, water use efficiency and uptake of N and P by the corn plants may be due to the increase in the amount of available P, K, Fe, Mn, Zn and Cu. Also, to the low release of K from glauconite which lead to a decrease in its leaching compared with the readily soluble and leachable K₂SO₄ fertilizer. This study yielded, identical results to that obtained by Petkova et al. Akhtar and Jenkins, Heckman, Heckman and Tedrow, Eid and Morsy simultaneously.

It could be concluded that it is possible using fine glauconite at application rate of 15 Mgha^-1 as an alternative and sufficient source of potassium in sandy soils of Egypt. For using fine glauconite as a natural source of potassium nutriment, on a large scale, some future studies, probably with field experiments, are still needed. These studies should include the economic aspects of the application of glauconite.