الفهرس 
REVIEW OF LITERATURESOnly 14 pages are availabe for public view
 |  | from | 91 |  |  |
| | | from | 91 | | |
Abstract
This work aims to study the effect of fertigation management under long-term drip irrigation conditions on some parameters of soil fertility in newly reclaimed areas, especially concerning the distribution of nutrients in a available form and the change in the ability of the soil to supply growing plants with water and air under the conditions of the newly reclaimed areas. To fulfill this aim samples were taken for two crops, avocado at different depths. Soil samples were collected to study the change in some parameters of soil physical and chemical properties related to soil fertility in sandy soil response to long-term drip fertigation management for avocado and banana crops.
Effects of long-term drip fertigation on soil physical characteristics
Results show the response of the different surface and subsurface soil layers at parallel or perpendicular to irrigation drip lines to about 30 years of drip fertigation. It could be observed that there is no change in the clay contents in the surface soil layer (0-25 cm depth) of the tested soil profiles taken around the tree trunk in either parallel or perpendicular on drip irrigation lines comparing with control soil.
Results revealed that the average clay contents decreased from 8.12% in the control treatment (the non-fertigated soil) to 6.45 and 5.90 at 1 and 2 m from tree and decreased to 6.18 and 5.44% at parallel and perpendicular on drip irrigation lines respectively as influenced by the long-term drip fertigation. The highest clay contents were found in the deeper layers of soil profiles taken parallel to drip irrigation lines.
As expected in such arid region, soil organic matter in the non- fertigated soil were 0.19, 0.18, 0.11 and 0.11 % at 0-25, 25-50, 50-75 and 75-100 cm with average value of 0.15 %. The organic matter contents in the fertigated soil markedly increased from 0.15 in the control treatment to
Salma M. A. M. Khamis (2024), M.Sc. Fac. Agric., Ain Shams Univ.
0.49and 0.51% in parallel soil profiles with drip irrigation lines and to 0.51 and 0.39% in perpendicular soil profiles on drip irrigation lines at 1 and 2 m from tree respectively.
The pH values of the non-fertigated soil were slightly alkaline, where its values ranged between 7.74-7.94 with an average of 7.81 average. It could be observed that the long-term drip fertigation had a slight effect on soil pH of all the tested soil profiles either at parallel or perpendicular on drip irrigation lines at 1 or 2 m from tree. The average values of pH decreased from 7.81 in control to 7.58 and 7.52 at 1 and 2 m from tree parallel to drip irrigation lines and decreased to 7.34 and 7.36 at 1 and 2 m from tree parallel to drip irrigation lines respectively.
The long-term drip fertigation in the studied area had no substantial effects on the available potassium (K), magnesium (Mg), zinc (Zn), manganese (Mn) and copper (Cu) contents in the tested soil profiles either in parallel or in perpendicular on drip irrigation lines.
Electrical conductivity (EC1:5) values ranged from 0.13 to 0.18 dS/m in soil samples taken from the non-fertigated soil (0.15 dS/m average). In general, the values of electrical conductivity (EC1:5) were very low either in fertigated or non-fertigated soil. Its values ranged between 0.11-0.26 dS/m. Results indicated a slight increase in salt accumulation after long-term (about 30 years) drip fertigation particularly at depth of 50- 100 cm in perpendicular direction on drip irrigation lines. It could be also observed a slight decrease in salt accumulation after long-term drip fertigation at depth of 50-100 cm in parallel direction to drip irrigation lines.
Soil fertility assessment after long-term of drip fertigation in newly area
The logical function tool as explained in Excel 16 could be used easier for assessment the expected effects of any of the soil properties under investigation on soil fertility, and then can be evaluate the class of soil fertility and the relative changes in soil fertility after about thirty years of soil drip fertigation.
The logical (IF) functions can be used for assessment of some soil fertility parameters in different categories as follow:
CEC Category =IF(CEC<=4,”VL”,IF(CEC<8,”L”, IF(CEC<16,”M”,IF(CEC<24,”G”, IF(CEC>=24,”VG”, ”X”)))))
SP Category =IF(SP<=15,”VL”,IF(SP<25,”L”,IF( SP<35,”M”,IF(SP<45,”G”,IF(SP>=45,”VG”, ”X”)))))
Permeability category =IF(Perm<=2.5,”VL”,IF (Perm<5,”L”,IF(Perm<10,”M”,IF(Perm<15,”G”, IF(Perm
>=15,”VG”,X)))))
CaCO3 category =IF(CC<=2,”VG”,IF(CC<5,”G”, IF(CC<10,”M”,IF(CC<25,”L”, IF(CC>=25, ”VL”,X))) ))
OM category =IF(OM<=0.5,”VL”,IF(OM<2,”L”, IF(OM<5,”M”,IF(OM<10,”G”, IF(OM>=10, ”VG”,”X” )))))
pH category =IF(pH<=5.1,”VG”, IF(pH<6.1,”G”, IF(pH<7,”M”,
IF(pH<8.5,”L”,IF(pH>=8.5, ”VL”, ”X”) ))))
EC category
=IF(EC<=0.25,”VG”,IF(EC<0.5,”G”,IF(EC<1.0,”M”,IF(EC<1.5,”L”,IF(E C>=1.5, ”VL”,”X” )))))
P category =IF(P<=20,”VL”,IF(P<40,”L”,IF(P<60
,”M”,IF(P<80,”G”,IF(P>=80, ”VG”,”X”)))))
K category =IF(K<=150,”VL”,IF(K<250,”L”,IF(K
<400,”M”,IF(K<600,”G”,IF(K>=600,”VG”, ”X”)))))
Ca category
=IF(Ca<=100,”VL”,IF(Ca<200,”L”,IF(Ca<400,”M”,IF(Ca<600,”G”, IF(Ca>=600,”VG”,”X”) ))))
Mg category
=IF(Mg<=25,”VL”,IF(Mg<100,”L”,IF(Mg<250,”M”,IF(Mg<400,”G”,IF( Mg>=400,”VG”, ”X”)))))
Fe category
=IF(Fe<=5,”VL”,IF(Fe<10,”L”,IF(Fe<15,”M”,IF(Fe<25,”G”,IF(Fe>=25,” VG”, X)))))
Zn category
=IF(Zn<=1,”VL”,IF(Zn<3,”L”,IF(Zn<5,”M”,IF(Zn<8,”G”,IF(Zn>=8,”VG ”,”X”)))))
Mn category =IF(Mn<=4,”VL”,IF(Mn<8,”L”,IF( Mn<12,”M”,IF(Mn<16,”G”,IF(Mn>=16,”VG”, ”X”)))))
Cu category =IF(Cu<=0.3,”VL”,IF(Cu<0.8,”L”, IF(Cu<1.2,”M”,IF(Cu<2.5,”G”, IF(Cu>=2.5, ”VG”,”X”)) )))
Concerning, soil parameters assessments in different categories using logical function, data revealed that the total indices of the tested soil parameters related to soil fertility were 33.3 (100), 36.5 (109) and 37.5 (111.3) with soil fertility class of L (Low), L and L for the control (non- fertigated soil) and at 1 and 2 m from tree in parallel to drip irrigation line respectively. In addition, the total indices of the tested soil parameters at 1 and 2 m from tree at vertical to drip irrigation line were 37.0 (111.3) and
36.5 (109.8) with soil fertility class of L and L respectively. The soil fertility class at parallel and perpendicular to drip irrigation line were 36.8 (110.5) and 36.7 (110.1) with soil fertility class L and L respectively.
The relative change in soil fertility class as influenced by the long- term cultivation with fertigation was evaluated using the TSFPI and pre- suggested total soil fertility parameters indices (STSFPI) as reference. The following is the logical function used for the estimation of the soil fertility class according to the suggested total soil fertility parameters indices:
(TSFPI)=IF(TSFPI<22.5,”VL”,IF(TSFPI<=37.5,”L”,IF(TSFPI<=52.5,”M ”,IF(TSFPI<=67.5,”G”, IF(TSFPI<=75,”VG”)))))
Results showed that the relative change in soil fertility were about 100 and 109% for the control (non-fertigated soil), at 1 and 2 m from tree in parallel to drip irrigation line respectively. The relative changes in soil fertility of the tested soil at 1 and 2 m from tree at perpendicular on drip irrigation line were about 111 and 110% respectively.
Conclusion
from the afore mentioned results, it could be concluded that the soil fertility class (SFC) of the investigated soil changed as affected by the long term of drip fertigation management for about 30 years by about 7 and 11
% and 12 and 10 % relative to the non-fertigated soil at 1 and 2 m from tree in parallel and perpendicular to drip irrigation lines respectively. The highest change in soil fertility after the long term of drip fertigation management was about 12 % relative to non-fertigated soil at 100 cm away from tree trunk in perpendicular on drip irrigation line. This followed by about 11% at 200 cm away from tree trunk in parallel to drip irrigation line. However, the relative best soil fertility class was associated with the highest soil fertility change particularly in such sandy soil.