Effect of Foliar and Soil Application of Phosphorus on Phosphorus Uptake, Use Efficiency and Wheat Grain Yield in Calcareous Soil
S.F. Al Harbi,
Foliar fertilization is a widely used practice to correct
nutritional deficiencies in plants caused by improper supply of nutrients to
roots. Most of the important agricultural soils in the Kingdom of Saudi Arabia
suffer from severe P deficiency. This is attributed to the high soil pH due
to the presence of calcium carbonate. Under such conditions, the utilization
by plants of fertilizer P is generally very low due to sorption of P by soils.
The objectives of this study were to determine the response of wheat to four
levels of foliar P application (0, 3, 6 and 12 kg P ha-1) under various
levels of soil P application rates (0, 150 and 450 DAP ha-1) on P
concentrations, soil available P and wheat yield cultivated in calcareous soil.
Foliar P fertilizer was applied at Feekes growth stage 7 (two nodes detectable)
and Feekes 10.5 (flowering completed). The results suggested that application
of 150 kg DAP ha-1 is quite enough to achieve the highest wheat grain
yield under the current experiment. Results revealed that foliar application
of P at Feekes physiological growth stage 7 generally increased wheat grain
yield and P uptake versus no foliar. Results confirmed the beneficial effect
of foliar P fertilization especially in the absence of soil P fertilizer application.
Soil available P values obtained at the end of growing period increased significantly
with increasing rates of added P. Thus, application of P fertilizer by foliar
along with medium rates of soil P fertilizer may contribute to improve P fertilizer
efficiency and increase wheat grain yield in calcareous soil.
Received: September 04, 2012;
Accepted: December 13, 2012;
Published: February 01, 2013
Phosphorus (P) is an essential nutrient required by plants for normal growth
and development. Most of agricultural soils of the Kingdom of Saudi Arabia suffer
from sever P deficiency (Bashour et al., 1983).
The availability of P to plants for uptake and utilization is impaired in alkaline
and calcareous soil due to the formation of poorly soluble calcium phosphate
minerals. Adding fertilizer P at normal rates and with conventional methods
may not result in optimal yield and crop quality in these soils common in arid
and semi-arid regions. The formation of insoluble compounds due to soil chemical
reactions limits the plant available P making phosphate fertilization use efficiency
very low by crops (Barber, 1995) Further more Sahin
et al. (2007), have pointed out that fertilizer usage and precipitation
level are substantial inputs for producing high wheat yield. In addition, in
respect for their model, fertilizer usage affects wheat yield more than precipitation
level. Therefore, appropriate management of phosphate fertilizers is a major
concern. Also, stimulated by economic as well as environmental concerns, the
efficient use of P is becoming more and more important (Kaeppler
et al., 1998). Some researchers concluded that in corn and other
cereals crops, foliar P was not important (Haq and Mallarino,
2000). Others advocated foliar fertilization (Eddy, 2000)
as a viable economical way of supplementing the plants nutrients for more
efficient fertilization. Foliar treatment of P can be applied only when the
crop needs it and thus decrease cost of production (Faulkner,
1999). The major reason for continued P applications to the soil is to maintain
reserves in the soil since foliar P might not directly contribute to the soil
P level which is very important at the very early stage of growth. However,
in cropping systems involving corn stock chopping and incorporation, some proportion
of P will be returned to the soil in an organic form contributing to the soil
P. Foliar P is very effective in high fixing soils since having P applied to
the soil would not help the plant in the long run due to formation of insoluble
aluminum, iron and calcium phosphate compounds. In P rich soils it may be preferable
to apply foliar P on the leaves if a deficiency is expected and demands are
high (Silberbush, 2002). This will not only increase
efficiency and decrease cost of production but also reduce runoff of soil apply
P, which is responsible for eutrophication of many lakes and streams (Sharpley
et al., 1994).
Several factors including plant management and environmental factors influence
the benefit of foliar P applied. Foliar application should be made when the
plant is not in water stress, either too wet or too dry (Denelan,
1988). The most critical times to apply are when the crop is under P stress
which occurs during periods of active plant growth. This is likely when the
plant is changing from a vegetative to a reproductive stage.
Availability of the different nutrient elements is directly affected by the
chemical and physical properties of soils (Sharpley, 1983).
It is thought that foliar application of P could reduce the negative impact
of some soil properties (Eddy, 2000). Studies conducted
elsewhere demonstrated the positive response of foliar application of P in wheat
and corn yields (Latif et al., 1994). Therefore,
the objectives of this study were to assess the suitability of foliar P application
under various levels of soil application on P uptake, available soil P content
and wheat yield in calcareous soil.
MATERIALS AND METHODS
Study area and experimental design: Field experiment site was established in the fall of 2007 at the College of Agricultural Experimental and Research Farm at Dirab, 25 km of South Riyadh, Kingdom of Saudi Arabia. The soil was air-dried, ground and passed through a 2 mm sieve. Some physical and chemical properties of the soil are presented in Table 1. A Completely Randomized Block Design (CRBD) with three replications was used. The plots were 3 m by 3 m in size.
Soil and foliar treatments: Soil application levels of P (0, 150 and
450 DAP ha-1) as diammonium phosphate applied just before sowing.
Varying foliar P application rate of 0, 3, 6 and 12 kg P ha-1 was
applied as NH4H2PO4 solution with a pulse modulated
handheld sprayer applied at Feekes physiological growth stage 7 (second node
of stem formed) and Feekes growth stage 10.5 (flowering completed) as described
by (Large, 1954). Nitrogen @ 165.6 kg N ha-1
as urea was applied to all the treatments in six equal splits during the growth
stage. Potassium was applied @ 22 kg K ha-1 as foliar on three equal
splits. The winter wheat variety used was (Yocora Rojo) planted in November.
Irrigation was performed using the surface irrigation with water quality presented
in Table 2.
|| Some physical and chemical characteristics of calcareous
|OM: Organic matter, EC: Electrical conductivity
|| Water quality used for irrigation the experiment
|EC: Electrical conductivity
Uniform cultural practices were carried out to each treatment plot throughout
the crop growth period.
Plant sampling and measurements: Plant samples were collected at growth stage 7 and 10.5. The crop was harvested at maturity. Grain samples were taken and dried in a forced-air oven at 65°C, ground to pass a 140 mesh sieve and analyzed for total P. Soil samples also were collected after harvesting and analyzed for available P.
Statistical analysis: All obtained collected data were analyzed statistically
and the significant (p<0.05) differences among the mean was analyzed by the
SAS analytical tools (SAS, 1985).
RESULTS AND DISCUSSION
Effect of treatment on wheat grain yield: Table 3
shows the effect of soil, foliar P application rates and timing of application
on wheat grain yield. Soil phosphorus application in combination with different
levels of foliar P showed significant differences in grain yield. The average
yield of wheat was 4.67, 5.81 and 5.71 ton ha-1 for 0, 150 and 450
kg DAP ha-1, respectively. Results indicated that increase of soil
application to 450 kg DAP ha-1 resulted in slight non-significant
decrease in wheat grain yield compared to 150 kg DAP ha-1. This results
indicated that application of 150 kg DAP ha-1 is quite enough to
achieve the highest grain yield under the current experiment. Foliar application
rates resulted of 3, 6 and 12 kg P ha-1 in a percent increment of
11.2, 22.8 and 32%, respectively over the control. A significant increase in
wheat grain yield was observed at Feekes growth stage 7 when compared with Feekes
10.5. Alam et al. (2002) reported higher grain
yield of wheat due to fertigation of P at first irrigation compared to its incorporation
at sowing. Application of soil P with supplement foliar P resulted in a better
grain yield in most instances where significant was observed.
|| Significant interactions between rate of applied P, foliar
P and time of application of foliar P on wheat yield
|LSD(0.05) for P rate = 499, for F rate = 576 and
for interaction = 1411, T1: Feekes growth stage 7, T2: Feekes growth stage
10.5, DAP: Diammonium phospahte
|| Significant differences in P concentration in plant as a
result of time and rate of foliar-applied P
|LSD(0.05) for P rate: 0.01, for F rate: 0.01 and
for interaction: 0.02, T1: Feekes growth stage 7, T2: Feekes growth stage
10.5, DAP: Diammonium phospahte
This suggests that wheat grain yield can be improved by supplementing P in
foliar form when the plant is in need.
Effect of soil, foliar P application and timing of application on P concentration:
Grain P concentration was influenced by levels of both soil, foliar and time
of application (Table 4). Maximum P content recorded at 450
kg DAP ha-1 which was significantly higher than control and 150 kg
DAP ha-1. Foliar application of P at Feekes physiological growth
stage 7 generally increased grain P content versus no foliar P. The results
showed that foliar P application enhanced the grain wheat yield, P concentration
and agronomic efficiency significantly over the soil application. This may be
explained that a long time interaction (aging) of soluble P with soil led to
its reaction with solid phase of soil, calcium carbonate and the formation of
relatively insoluble reaction products with Ca, Fe and Al leading to P fixation
(Brady and Weil, 2002). All these processes leading to
fixation are delayed when applying P fertilizer through foliar as plant absorbed
this nutrient quickly and directly from the soil solution. In addition, the
positive effect of fertigation may also be due to optimum moisture in the soil
at appropriate time along with fertilization, which facilitated maximum utilization
of applied P to crops (Stewart et al., 2005).
Available soil P content: The different rates of soil P applied have
a significant effect on the level of available P soil content (Table
5). The available P reached 18.3 mg kg-1 under application of
450 kg DAP ha-1 resulting in 313% increase over control.
||Relationship between available soil P content and soil P rates
applied without foliar P application
However, the high increment of available P did not correspond to similar increase
in grain yield (Table 3). Significant increases in available
soil P content followed the increase in foliar applied P; however the time of
foliar application showed a slight effect on soil available P. The amount of
fertilizer required to maintain the initial soil test can be determined graphically
by plotting soil test level as a function of the applied fertilizer rate (Fixen
and Ludwick, 1983). In the present work, the amount of fertilizer required
to maintain the soil P test at 10 mg kg-1 (the minimum required available)
in the studied soil was estimated to be 250 kg DAP ha-1 (Fig.
1). This value was less than the rates of 3, 6 and 12 kg P ha-1,
respectively. The results indicated that, under the conditions of this experiment,
the quantities of P fertilizer to be added to raise the P level was relatively
very high when using only soil application, value reported by several researchers
on the calcareous soils of Saudi Arabia (Ayed and Sayed,
1985; Al-Mustafa et al., 1995).
|| Effect of interaction between rate of soil P, foliar P and
time of foliar P application on available soil content
|DAP: Diammonium phospahte, LSD(0.05) for soil P
rate: 0.80, for foliar rate: 0.90 and interaction: 1.18. T1: Feekes growth
stage 7, T2: Feekes growth stage 10.5
||Relationship between available P soil content and soil P rates
applied with foliar P rates at (a) 3, (b) 6 and (c) 12 kg P ha-1
The results showed additions 450 kg DAP ha-1 in combination with
foliar P rates of 3, 6 and 12 kg P ha-1 resulted in high levels of
available soil P (16.2, 18.9 and 23.3 mg kg-1), respectively. On
the other hand, application of 150 kg DAP ha-1 combined with foliar
P application rates of 3, 6 and 12 kg P ha-1 resulted in 8.70, 10.3
and 13.5 mg kg-1, respectively (Fig. 2). This means
that, the quantities required to raise the level of P are 225, 160 and 90 kg
DAP ha-1 in the case of additions foliar P while the application
of foliar P would reduce the soil P application rate and subsequently increase
the P efficiency. These results are in a good accordance with the data reported
by Modaish et al. (2005).
The presented results indicated that use of foliar P fertilization in wheat have a beneficial effect on use efficiency of phosphorus fertilizer. The application of foliar P proved to be beneficial especially, when combined with medium rates of soil applied P. There a need for further trials using various soil phosphorus rates near 150 kg DAP ha-1 al to determine the exact optimum rate of soil applied P. The optimal rate of soil applied be The lower efficiency of soil added P in the calcareous soils should be addressed by testing different methods of applications that could raise efficiency of P fertilizers. The presented results should be pursued further to obtain the best combinations of soil added and foliar P application that would give the best P use efficiency.
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