Status and Distribution of Different Potassium Forms in Calcareous Soils in Northern Iraq

Abstract

1n the last few years, the demand increased especially in the developing countries for food production. One of the parameters to increase the production quantitatively and qualitatively is the use of fertilizers by following the modern techniques in fertilization which needs a detail soil studies. This study highlighted on behavior of different forms of potassium, their distributions through soil profile, and the relationships between them and with soil other properties. To represent a detailed study of the potassium behavior, twenty two surface (0-15cm) and subsurface (15-30cm) soil samples were selected from Nineveh province. The soil chemical and physical properties of each location are different. Distribution of different forms of K in these soils, i.e., available, water soluble (H2O-K), exchangeable (NH4OAc-K), non-exchangeable (HNO3-K), mineral and Total forms were ranged from (0.708 to 1.167),(0.006 to 0.146), (0.691 to 1.124), (1.150 to 3.261), (35.48 to 52.81) and (38.78 to 58.65) respectively, for surface soil and (0.559-0.997),(0.003-0.105), (0.554 to 0.914), (0.997 to 2.801), (30.04 to 56.77) and (32.55 to 60.88) respectively, for sub-surface soil. Correlation study showed that the various forms of K were positively and significantly correlated amongst themselves and with CaCO3 content of the soils negatively. The water soluble, exchangeable; available; nonexchangeable and mineral potassium constituted only 0.075; 1.65 ;.1.73; 3.95 and 92.03 percent of the total-K respectively.

Potassium Forms for Main Soil Orders in The North of Iraq

“…In the table (4) shown that exchangeable K had highly significant correlation with available K, non-exchangeable-K and silt content with the correlation coefficient values or r = 0.96**, r= 0.75**, and r= 0.80** respectively and significant positive correlated with total-K (0.067*) and negatively correlated but nonsignificant with CEC (-0.44). Without CEC, these results are agreeing with the results found by AL-Badrani and Radhwan (2019). The exchangeable potassium is more related to the type and amount of clay and its net negative charge (Parfitt, 1992).…”

“…Table (4) illustrates a significant and positive relationship between available potassium with non-exchangeable-K (r=0.71**), total-K (r=0.67*) silt (r=0.80**) while negative nonsignificant correlation observed to CEC (-0.46). These results are similar to those noted by (Saini and Grewal, 2014;AL-Badrani and Radhwan, 2019). The positive correlations between forms of potassium with other forms point out that the available-K is governed by the other forms of potassium in the soil.…”

“…The distribution of available-K according to the horizons ranged from (97 -246), (72 -216) and (70 -186) mg kg -1 (Table 3) from the surface horizon to middle and third horizons respectively, This increase of available-K in surface and decrease in sub surface horizon is similar to the distribution of exchangeable potassium and similar causes effect on it. Similar finding were also described by (Siddiqua et al, 2018;AL-Badrani and Radhwan, 2019). The available potassium for Semeel, Imerik, Gerderash, Perdi and Wermawa pedons represent 5.476, 4.628, 4.039, 5.660 and 3.000 of the total potassium respectively.…”

“…The pattern distribution of water soluble potassium in studied soil indicated to decrease in soluble K with increase in soil depth, which ranged from (12 -40), (5 -26) and (4 -14) mg kg -1 (Table, 3) this decrease of soluble K agrees with the decrease of organic matter and EC while disagrees with pH and clay percent (Table,2). Similar results were found by (Raskar and Pharande, 1997;AL-Badrani and Radhwan 2019). The soluble potassium in Semeel, Imerik, Gerderash, Perdi and Wermawa represent 0.656, 0.306, 0.302, 0.950 and 0.147 of the total potassium respectively.…”

“…The amount of exchangeable K according to the horizons ranged between (82 -229), (67 -214) and (68 -191) mg kg -1 (Table 3) from the surface to subsurface horizons respectively, The higher concentration of exchangeable-K in surface horizon could be due to high organic matter content, use of K fertilizers, decomposing of crop residue, and a high degree of weathering process in the surface horizon compared to the lower horizons, the release of soluble K from crop residue. These results were parallel with those observed by (Saini and Grewal., 2014;AL-Badrani and Radhwan (2019).The exchangeable potassium for Semeel, Imerik, Gerderash, Perdi and Wermawa pedons represent 4.92, 4.529, 3.503, 4.456 and 2.695 of the total potassium respectively.…”