Organic fertilization system
In the organic fertilization system, an increase was observed in exchangeable cations with the increase in the amount of organic manure in the soil. As it is known, the increase in the content of exchangeable cations is closely related to the increase in organic matter in the soil. Regardless of its origin, organic matter added to the soil increases the amount of exchangeable cations in the soil (Fernandez et al., 2016). The exchangeable calcium contents of the soil increased also for two years. However, the effect of applied organic manures on the exchangeable calcium content of the soil was not statistically significant in the first year, but significant in the second year (p < 0.05). With the addition of organic manure to the soil, the increase in the exchangeable calcium content increased by 6.6% in the first year and by 9.6% in the second year (Table 2). According to the data of both years, the highest exchangeable calcium content was obtained from M4 application (8.71 me 100 g− 1). The greater increase in the second year may be due to the accumulation of organic matter in the soil and the mineralization of calcium. Calcium bound in the soil is desorption by the effect of organic matter and can pass into the soil solution (Shen et al., 2011).
Table 2
Exchangeable cations of the soil as affected by manure applications.
Manure doses | ECa (me 100 g− 1) | EMg (me 100 g− 1) | EK (me 100 g− 1) | ENa (me 100 g− 1) |
2019-20 | 2020-21 | 2019-20 | 2020-21 | 2019-20 | 2020-21 | 2019-20 | 2020-21 |
M0 | 8.14a | 7.95c | 1.30e (ef) | 1.27c (f) | 0.58c (d) | 0.65b (c) | 0.042a | 0.038a |
M1 | 8.27a | 8.08bc | 1.46d (c) | 1.34bc (de) | 0.66b (c) | 0.66b (c) | 0.044a | 0.039a |
M2 | 8.26a | 8.07bc | 1.35c (de) | 1.36b (d) | 0.71a (bc) | 0.66b (c) | 0.046a | 0.039a |
M3 | 8.68a | 8.52ab | 1.50b (bc) | 1.46a (c) | 0.68b (bc) | 0.70a (bc) | 0.047a | 0.043a |
M4 | 8.67a | 8.71a | 1.68a (a) | 1.53a (b) | 0.79a (a) | 0.72a (b) | 0.051a | 0.043a |
Means | 8.41A | 8.27A | 1.46A | 1.39B | 0.69A | 0.68A | 0.046A | 0.040B |
F-values | | | | | | | | |
M | 2.74ns | 4.98* | 211.9** | 18.28*** | 9.62** | 9.91** | 1.07ns | 0.65ns |
Y | 2.11ns | 31.28*** | 0.11ns | 7.51* |
M x Y | 0.11ns | 7.05** | 4.13* | 0.20ns |
ECa: Exchangeable calcium, EMg: Exchangeable magnessium, EK: Exchangeable potassium, ENa: Exchangable sodium; M0 to M4: No manure, and 10, 20, 30,40 t ha− 1 dairy manure applications, respectively; Statistically significant at (*p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001; ns, not significant). Column means with the same letter are not significantly different by Duncan’s multiple range test (p < 0.05). Letters in parentheses indicate manure x year interaction. Capital letters indicate the results of the Duncan’s test between years.
In the experiment, the exchangeable magnesium contents increased in both years with the effect of organic manure. This increase was statistically significant in both years (p < 0.01; p < 0.001). While the increase in the exchangeable magnesium content in the soil was 29.2% in the first year, it was recorded as 20.5% in the second year (Table 2). However, the manure x year interaction was found to be statistically significant (p < 0.01). In both years, the highest exchangeable magnesium content in the soil was determined in the M4 application in the first year of the experiment (1.68 me 100 g− 1). The differences in exchangeable magnesium contents between years were also found to be statistically significant (p < 0.001). In the preliminary manure analysis, the magnesium content in the organic fertilizer was already high. However, with the addition of organic matter, it became inevitable to increase the exchangeable magnesium content in the soil when combined with the magnesium existing in the soil (Angelova et al., 2013).
The exchangeable potassium contents in the soil increased with the increase of organic manure applied. Statistically significant relationships were found between the organic manure applied and the exchangeable potassium content of the soil (p < 0.01). However, the interaction of organic manure x year was also found to be statistically significant (p < 0.05). According to the data obtained at the end of both years, the highest exchangeable potassium content in the soil was obtained from M4 application in the first year (0.79 me 100 g− 1). Besides, organic fertilizers increased the exchangeable potassium content of the soil by 36.2% in the first year and by 10.8% in the second year (Table 2). The decrease in the rate in the second year compared to the first year may be related to the saturation of the potential potassium content in the soil. The amount of potassium in organic manures can increase the exchangeable potassium amount in the soil (Siregar et al., 2005; Shen et al., 2011; Whittinghill and Hobbie, 2012).
Table 3
Cation exchange capacity and base saturation rate of the soil as affected by manure applications.
Manure doses | CEC (me 100 g− 1) | BSR (%) |
2019-20 | 2020-21 | 2019-20 | 2020-21 |
M0 | 10.7c | 10.5d | 94.4a | 94.1a |
M1 | 11.5b | 11.2c | 90.6bc | 90.3b |
M2 | 11.3bc | 11.3c | 91.7ab | 89.9b |
M3 | 12.4a | 12.2b | 88.2c | 87.8c |
M4 | 12.8a | 12.9a | 87.5c | 85.6d |
Means | 11.7A | 11.6A | 90.5A | 89.6A |
F-values | | | | |
M | 11.64*** | 28.24*** | 7.79** | 80.15*** |
Y | 0.76ns | 3.72ns |
M x Y | 0.20ns | 0.58ns |
CEC: Cation Exchange capacity, BSR: Base saturation rate; M0 to M4: No manure, and 10, 20, 30,40 t ha− 1 dairy manure applications, respectively; Statistically significant at (*p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001; ns, not significant). Column means with the same letter are not significantly different by Duncan’s multiple range test (p < 0.05). Capital letters indicate the results of the Duncan’s test between years.
However, it increased the exchangeable sodium content of the soil by being affected by the existing salt ratio in the amount of organic manure applied. In addition, this increase was not statistically significant (Table 2). The exchangeable sodium content of the soil increased by 21.4% in the first year and by 13.2% in the second year. However, the exchangeable sodium content of the soil decreased in the second year compared to the first year, and this was statistically significant (p < 0.05). Depending on the types of organic manures, the sodium content may also vary due to the amount of salt in them. Organic manures added to the soil can also increase the salt content of the soil (Demirtaş et al., 2012; Erdal et al., 2018).
According to the results of the experiment, it was determined that the organic manure added to the soil increased the cation exchange capacity (CEC) of the soil. However, the effect of organic manures on the CEC of the soil was found to be statistically significant in both years (p < 0.001). While the increase in the first CEC was 19.6% in the experiment, it was recorded as 22.9% in the second year. In both years, the highest CEC was obtained from M4 application (12.8 and 12.9 me 100 g− 1, respectively). However, no statistically significant difference was found between the years (Table 3). The CEC of the soil increased stably in both years. It is directly related to the amount of organic matter in the soil. It has also been reported in many studies that the organic matter added to the soil increases the CEC (Francou et al., 2005; Kasongo et al., 2011; Whittinghill and Hobbie, 2012; Gayathri et al., 2019).
On the contrary, the base saturation ratio (BSR) decreased as the amount of organic manure applied increased. Meanwhile, by 7.3% decrease was recorded in the first year of the study, by 9.0% decrease was detected in the second year (Table 3). The BSR is the ratio of the total exchangeable cations in the soil to the cation exchange capacity, and this ratio increases with the increase in the amount of the total exchangeable cations in the soil, on the contrary, it decreases with the increase of the cation exchange capacity. This situation is closely related to the desorption of saturated cations. The exchange capacity of the cations separated from the solid phase increases and is offered to the plant in the forms that the plant can take, so the BSR in the soil decreases (Dengiz et al, 2007; Wuddivira and Camps-Roach, 2007; Osman, 2013).
Conventional Phosphorus Fertilization System
In the conventional phosphorus fertilization system, increasing doses of mineral phosphorus were applied and the effect on the content of exchangeable cations in the soil was not found statistically significant (Table 4).
Although an increase in the exchangeable calcium content was noted up to P2 application, decreases were detected at subsequent doses. Meanwhile, the effect of phosphorus doses on exchangeable magnesium content was statistically significant in the first year of the study, it was insignificant in the second year (p < 0.01). Exchangeable magnesium content increased by 6.2% in the first year and increased by 3.1% in the second year. In addition, the difference in exchangeable magnesium content between years was found to be statistically significant (p < 0.01). Compared to the first year, the exchangeable magnesium content in the soil decreased in the second year. The effect of mineral phosphorus doses on the exchangeable potassium contents of the soil was not statistically significant for two years. However, the exchangeable potassium content of the soil increased in the second year of the study and this was statistically significant (p < 0.01). Moreover, the highest exchangeable potassium content was recorded at the P2 dose (0.69 me 100 g− 1). Also, the effect of mineral phosphorus doses on the exchangeable sodium content of the soil was not statistically significant. The CEC and BSR of soils were not affected by mineral phosphorus applications. According to the results obtained, the effect of mineral phosphorus doses on the CEC and BSR were not statistically significant during both study years (Table 5). Also, the highest CEC was recorded at the P2 dose (11.2 me 100 g− 1) in the first year of the study.
Table 4
Exchangeable cations of the soil as affected by phosphorus applications.
Phosphorus doses | ECa (me 100 g− 1) | EMg (me 100 g− 1) | EK (me 100 g− 1) | ENa (me 100 g− 1) |
2019-20 | 2020-21 | 2019-20 | 2020-21 | 2019-20 | 2020-21 | 2019-20 | 2020-21 |
P0 | 8.14a | 7.95a | 1.30a | 1.27a | 0.58a | 0.65a | 0.042a | 0.038a |
P1 | 8.45a | 8.26a | 1.34a | 1.31a | 0.64a | 0.68a | 0.042a | 0.040a |
P2 | 8.53a | 8.37a | 1.30a | 1.30a | 0.69a | 0.69a | 0.042a | 0.041a |
P3 | 8.42a | 8.32a | 1.33a | 1.31a | 0.59a | 0.68a | 0.042a | 0.041a |
P4 | 8.08a | 8.23a | 1.38a | 1.30a | 0.64a | 0.67a | 0.040a | 0.041a |
Means | 8.32A | 8.23A | 1.33A | 1.30B | 0.63B | 0.67A | 0.042A | 0.040A |
F-values | | | | | | | | |
P | 1.89ns | 2.06ns | 2.84ns | 1.36ns | 2.03ns | 2.01ns | 0.11ns | 1.85ns |
Y | 1.38ns | 13.39** | 11.43** | 1.81ns |
P x Y | 0.67ns | 2.41ns | 1.26ns | 0.34ns |
ECa: Exchangeable calcium, EMg: Exchangeable magnessium, EK: Exchangeable potassium, ENa: Exchangable sodium; P0 to P4: No phosphorus, and 10, 20, 30,40 kg ha− 1 phosphorus fertilizer applications, respectively; Statistically significant at (*p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001; ns, not significant). Column means with the same letter are not significantly different by Duncan’s multiple range test (p < 0.05). Capital letters indicate the results of the Duncan’s test between years.
Table 5
Cation exchange capacity and base saturation rate of the soil as affected by phosphorus applications.
Phosphorus doses | CEC (me 100 g− 1) | BSR (%) |
2019-20 | 2020-21 | 2019-20 | 2020-21 |
P0 | 10.7a | 10.5a | 94.4a | 94.1a |
P1 | 10.9a | 10.9a | 95.7a | 94.4a |
P2 | 11.2a | 10.9a | 94.7a | 95.1a |
P3 | 10.8a | 10.9a | 96.2a | 94.9a |
P4 | 10.6a | 10.8a | 96.2a | 94.7a |
Means | 10.8A | 10.8A | 95.4A | 94.6A |
F-values | | | | |
P | 1.81ns | 1.93ns | 0.60ns | 0.23ns |
Y | 0.001ns | 1.50ns |
P x Y | 0.86ns | 0.34ns |
CEC: Cation Exchange capacity, BSR: Base saturation rate; P0 to P4: No phosphorus, and 10, 20, 30,40 kg ha− 1 phosphorus fertilizer applications, respectively; Statistically significant at (*p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001; ns, not significant). Column means with the same letter are not significantly different by Duncan’s multiple range test (p < 0.05). Capital letters indicate the results of the Duncan’s test between years.
Cations dissolved from carbonate minerals (Ca, Mg, Na and K) may tend to change by forming electrostatic bonds, especially with phosphorus at superficial levels, and/or cause precipitation of phosphates (Zhang et al., 2021). This depends on the alkaline potential of the soil. At high pHs, precipitation occurs by forming Ca and Mg-P phases. In some studies conducted in recent years, it has come to the fore that phosphorus applied in soils rich in Ca and Mg at high pH precipitates with electrostatic bonding rather than the change of these elements in the soil (Naveed et al., 2020; Geng et al., 2022). Therefore, it is reported that the effect of the phosphorus-to-cation exchange algorithm is not alone but under the influence of some environmental factors (Zhu and Dittrich, 2016).
Organomineral Phosphorus Fertilization System
The effects of sixteen different organomineral fertilizer combinations comprised of dairy cattle and mineral phosphorus doses on the content of exchangeable cations, cation exchange capacity, and base saturation rate during the study period were examined and its statistical evaluation is given in Tables 6 and 7.
Table 6
Exchangeable cations of the soil as affected by organomineral fertilizer applications
Organomineral fertilizer doses | ECa (me 100 g− 1) | EMg (me 100 g− 1) | EK (me 100 g− 1) | ENa (me 100 g− 1) |
2019-20 | 2020-21 | 2019-20 | 2020-21 | 2019-20 | 2020-21 | 2019-20 | 2020-21 |
M0P0 | 8.14a | 7.95a | 1.30j | 1.27j | 0.58e | 0.65f | 0.042a | 0.038a |
M1P1 | 8.44a | 8.25a | 1.41gh | 1.36hı | 0.69d | 0.68ef | 0.040a | 0.040a |
M1P2 | 8.54a | 8.35a | 1.42gh | 1.39gı | 0.71d | 0.71b-e | 0.039a | 0.041a |
M1P3 | 8.40a | 8.41a | 1.38hı | 1.35ı | 0.73cd | 0.69d-f | 0.039a | 0.040a |
M1P4 | 8.40a | 8.34a | 1.33ıj | 1.34ı | 0.69d | 0.68ef | 0.039a | 0.039a |
M2P1 | 9.05a | 8.39a | 1.45e-g | 1.41f-h | 0.75cd | 0.69d-f | 0.043a | 0.042a |
M2P2 | 8.63a | 8.59a | 1.42gh | 1.39gı | 0.73cd | 0.73a-c | 0.039a | 0.042a |
M2P3 | 8.62a | 8.71a | 1.43f-h | 1.37hı | 0.75cd | 0.71b-e | 0.041a | 0.043a |
M2P4 | 8.15a | 8.56a | 1.38hı | 1.35ı | 0.75cd | 0.70c-e | 0.042a | 0.042a |
M3P1 | 9.08a | 8.87a | 1.51c-e | 1.48de | 0.82bc | 0.73a-c | 0.043a | 0.043a |
M3P2 | 9.08a | 8.87a | 1.53cd | 1.50cd | 0.77cd | 0.73a-c | 0.044a | 0.043a |
M3P3 | 8.97a | 8.76a | 1.48d-f | 1.45ef | 0.75cd | 0.74ab | 0.046a | 0.042a |
M3P4 | 8.51a | 8.65a | 1.46e-g | 1.42e-g | 0.73cd | 0.74ab | 0.041a | 0.041a |
M4P1 | 8.78a | 8.78a | 1.63a | 1.59a | 0.93a | 0.74ab | 0.048a | 0.045a |
M4P2 | 8.92a | 8.93a | 1.60ab | 1.57ab | 0.88ab | 0.76a | 0.045a | 0.045a |
M4P3 | 9.22a | 8.80a | 1.64a | 1.53bc | 0.77cd | 0.76a | 0.045a | 0.044a |
M4P4 | 8.67a | 8.58a | 1.56bc | 1.52b-d | 0.75cd | 0.72a-d | 0.044a | 0.043a |
Means | 8.68A | 8.58A | 1.47A | 1.43B | 0.75A | 0.72B | 0.042A | 0.042A |
F-values | | | | | | | | |
OMF | 1.20ns | 1.77ns | 23.34*** | 24.64*** | 5.19*** | 3.67*** | 1.01ns | 0.80ns |
Y | 1.45ns | 31.59*** | 15.84*** | 0.20ns |
OMF x Y | 0.41ns | 0.72ns | 2.41ns | 0.38ns |
ECa: Exchangeable calcium, EMg: Exchangeable magnessium, EK: Exchangeable potassium, ENa: Exchangable sodium, Phosphorus x manure interactions are organomineral fertilizer combinations (OMF). Statistically significant at (*p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001; ns, not significant). Column means with the same letter are not significantly different by Duncan’s multiple range test (p < 0.05). Capital letters indicate the results of the Duncan’s test between years.
According to the results, although the effect of organomineral fertilizer combinations on the exchangeable calcium content of the soil was not statistically significant in both years, it was determined that the exchangeable calcium content of the soil increased. It was noted that organomineral fertilizers increased the exchangeable calcium content of the soil by 13.3% in the first year and by 12.3% in the second year. Among the combinations, the highest exchangeable calcium content in the soil was determined in the first year in M4P3, and in the second year in M4P2 application. However, it was determined that the increase in the exchangeable calcium content increased with the increase in the organic fertilizer content of the organomineral fertilizers. Mainly, the exchange of Ca, a base cation, is due to the electrostatic interaction between the clay minerals and/or the negative charge on the organic matter, so the adsorption depends on variables such as pH and ionic strength (Rytwo et al., 2002). Decreased pH and increasing organic matter amount in the soil increased the exchange capacity of Ca and provided its adsorbent on the colloid surface. The amount of exchangeable Ca increasing in line with the increasing organic matter content supports the results obtained from the experiment, as in many studies (Gustafsson and Van Schaik, 2003; Meier et al., 2004; Whittinghill and Hobbie, 2012).
The effect of organomineral fertilizer combinations on the exchangeable magnesium content of the soil was found to be statistically significant (p < 0.001). It was determined that the exchangeable magnesium content of the soil increased with the increase in the doses of organomineral fertilizers (especially the organic fertilizer content). The highest exchangeable magnesium content was recorded in the combination of M4P3 in the first year and M4P1 in the second year (Table 6). However, it was determined that organomineral fertilizer combinations increased the exchangeable magnesium content of the soil by 26.2% in the first year and by 25.2% in the second year. In the study, statistically significant differences were also obtained between the years (p < 0.001). According to the findings, the increasing amount of organic matter in the soil increased the exchangeable Mg amount of the soil in the same direction. Magnesium is a base cation and its adsorbance is quite high due to its electrostatic charge on the colloid surface compared to its high organic matter content (Angelova et al., 2013). However, many studies have shown similarities with the findings in the experiment, in which the change of Ca and Mg elements increases with the increase of organic matter in the soil and the decrease in pH values in the soil (Dijkstra, 2003; Reich et al., 2005; Guckland et al., 2009; Whittinghill and Hobbie, 2012). In addition, it was determined that as the applied phosphorus doses increased, the exchangeable Mg capacity first increased and then decreased. Phosphorus mineralization increased with the increase in organic matter in the soil, and the retained Mg element in the soil was activated for cation exchange. Therefore, it has been reported in some studies that phosphorus-bound Mg is stored in soil water in water-soluble forms for the benefit of the plant (Neirynck et al., 2000; Reich et al., 2005; Shen et al., 2011; Melenya et al., 2015).
The effect of organomineral fertilizers applied during the study period on the exchangeable potassium content of the soil was found to be statistically significant (p < 0.001). Depending on the doses of organomineral fertilizers, increases were recorded in the exchangeable potassium contents of the soils. In the study, organomineral fertilizer combinations increased the exchangeable potassium content of the soil by 60.3% in the first year and by 16.9% in the second year. This rapid increase in the first year compared to the second year may be due to the insufficient potassium content in the soil and the strong effect of both the potassium existing in the soil and the potassium present in the organic fertilizer together with the organomineral fertilizer combinations. In the second year, the situation became more stable, the potential potassium content in the soil became saturated and the rate of increase slowed down. Also, the highest exchangeable potassium content was determined in the M4P1 application in the first year, and in the M4P2 and M4P3 applications in the second year (Table 6). According to the findings obtained from the experiment, the increasing amount of organic matter in the soil increased the exchangeable K contents. It is reported that with the increase of organic matter and decrease in pH, the exchange of K, a base cation with high adsorbance in soil, increases and it can be found in forms that can be taken by the plant (Siregar et al., 2005; Whittinghill and Hobbie, 2012). In many studies, it has been stated that increasing organic matter in the soil increases the exchangeable K activation (Khoshgoftarmanesh and Kalbasi, 2002; Verma et al., 2005; Yalçın et al., 2018; Çimrin, 2020).
Table 7
Cation exchange capacity, and base saturation rate of the soil as affected by organomineral fertilizer applications
Organomineral fertilizer doses | CEC (me 100 g− 1) | BSR (%) |
2019-20 | 2020-21 | 2019-20 | 2020-21 |
M0P0 | 10.7e | 10.5g | 94.4a | 94.1a |
M1P1 | 11.5c-e | 11.3f | 91.8a-c | 91.4b-d |
M1P2 | 11.5c-e | 11.4e-f | 93.0ab | 92.0b |
M1P3 | 11.4de | 11.4e-f | 92.3a-c | 91.8bc |
M1P4 | 11.3de | 11.3f | 92.3a-c | 91.7bc |
M2P1 | 12.6a-c | 11.7d-f | 89.9c-e | 90.3de |
M2P2 | 12.0b-d | 11.9c-f | 90.4b-d | 90.7c-e |
M2P3 | 12.0b-d | 12.0b-f | 90.4b-d | 90.3de |
M2P4 | 11.4de | 11.9c-f | 90.4b-d | 89.5ef |
M3P1 | 13.0ab | 12.6a-c | 88.0d-f | 88.0g |
M3P2 | 12.8ab | 12.6a-c | 89.6c-e | 88.6fg |
M3P3 | 12.7ab | 12.4a-d | 88.5d-f | 88.4fg |
M3P4 | 12.1b-d | 12.4a-d | 88.5d-f | 87.9g |
M4P1 | 13.2ab | 12.9a | 86.1f | 86.4h |
M4P2 | 13.3a | 13.1a | 86.0f | 86.4h |
M4P3 | 13.4a | 12.9a | 87.2ef | 86.0h |
M4P4 | 12.7ab | 12.7ab | 86.6f | 85.7h |
Means | 12.2A | 12.1A | 89.7A | 89.4A |
F-values | | | | |
OMF | 4.76*** | 7.87*** | 5.78*** | 34.00*** |
Y | 1.96ns | 1.73ns |
OMF x Y | 0.41ns | 0.23ns |
CEC: Cation Exchange capacity, BSR: Base saturation rate; Phosphorus x manure interactions are organomineral fertilizer combinations (OMF). Statistically significant at (*p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001; ns, not significant). Column means with the same letter are not significantly different by Duncan’s multiple range test (p < 0.05). Capital letters indicate the results of the Duncan’s test between years.
The effect of organomineral fertilizers applied during the study period on the exchangeable sodium content of the soil was not statistically significant. However, it was determined that the increasing amount of organic fertilizer in organomineral fertilizer combinations increased the exchangeable sodium content of the soil (Table 6). In the study, the highest exchangeable sodium content was recorded in the M4P1 combination in the first year, and in the M4P1 and M4P2 combination in the second year. It was determined that the exchangeable sodium content of the soils increased by 14.3% compared to the control in the first year, and by 18.4 in the second year. According to the findings, organomineral fertilizer combinations applied in both years increased the exchangeable Na content of the soils. In some studies, it is reported that fertilizers of animal origin contain salt in different amounts depending on the type and breed of animals (Demir et al., 2003; Demirtaş et al., 2012; Erdal et al., 2018). The presence of organic matter in the soil helps to disperse Na and can be mobilized in a soluble form, possibly in a colloidal form (Leogrande and Vitti, 2019).
It was determined that the total exchangeable cation contents of the soil were increased by the application of organomineral fertilizers. It has been reported by many researchers that the increase in the content of exchangeable cations depends on the amount of organic matter in the soil (Whittinghill and Hobbie, 2011; Boethling, 2019; Timmer et al., 2020). The binding of cations to soil surface components results from the electrostatic interaction of the negative charge on organic matter, and thus cation adsorption is dependent on variables such as pH and ionic strength (Behera et al., 2010). The combination of electrostatic charge and high surface area allows clay-sized particles to dominate mineral-mineral, mineral-organic, mineral-metal, and mineral-water interactions in soils (Kleber et al., 2021). However, with the increase in phosphorus doses, low-level increases were recorded in the exchangeable cations level. These increases are due to the increase in the saturation of colloid-bound Ca as the amount of water-soluble P in the soil increases, and the increase in the binding strength of Ca and Mg-bound P to the colloid as the soil pH decreases in lime soils (Manimel et al., 2013).
Organomineral fertilizers composed of mineral phosphorus and dairy cattle manure combinations increased the cation exchange capacity of the soil for two years, and this was statistically significant (p < 0.001). Organomineral fertilizers increased the cation exchange capacity of the soil by 25.2% in the first year of the study and by 24.8% in the second year. The highest cation exchange capacity in the soil was recorded in the M4P3 combination in the first year of the study, and in the M4P2 combination in the second year (Table 7). The difference between years was not statistically significant. According to the findings, it was determined that organomineral fertilizer applications in the soil increased the cation exchange capacity depending on the increasing amount of organic matter (Fig. 2A). Organic matter gives significant strength to the soil in terms of increasing cation exchange. As a result of the width of its surface area and its electrostatic state, it is the only substance that has the ability to bind large amounts of cations and increase their exchange activation (Oorts et al., 2003). Many researchers have reported that soils rich in organic matter have high cation exchange capacity (Francou et al., 2005; Kasongo et al., 2011; Gayathri et al., 2019; Liu et al., 2020).
Base saturation capacity is an important soil chemical property with implications for both soil taxonomic classification and soil fertility. Base saturation is defined as the sum of the four basic cations (Ca, Mg, K and Na) relative to the total soil cation exchange capacity at pH 7.0 or 8.2 (Foth and Ellis, 2018). According to the results obtained from the experiment, it was determined that organomineral fertilizer applications reduced the base saturation capacity of the soil. The lowest base saturation rate was recorded in the M4P2 application in the first year, and in the M4P4 application in the second year (Table 7). In the study, organomineral fertilizer combinations reduced the base saturation rate by 8.9% in both years. The effect of organomineral fertilizers on the base saturation ratio was found to be statistically significant (p < 0.001). In many studies, it has been reported by researchers that the basic cations in the soil have a high exchange capacity in soils where organic matter is rich and decrease with the increase of organic matter (Fig. 2B) and decrease in pH values (Fig. 2C) in the soil and that basic cations pass into the soil solution in forms that can be taken by the plant (Wuddivira and Camps-Roach, 2007; Osman, 2013; Blanco, 2017; Alkharabsheh et al., 2021).