PERFORMANCE OF GRAPEVINES UNDER IRRIGATION SYSTEMS - Management, Performance, and Applications of Micro Irrigation Systems - page 256

80% recommended dose registered 22.37 and 31.00% higher dry fruit yield over drip
and furrow irrigation methods, respectively, even with the same level and method of
normal fertilizer application.
Roubelakis and Kleiwer [70] stated that fruit quality may be affected due to abun-
dant or insuffi cient available nitrogen. They also found that the total amount of nitrog-
enous compounds in grapevines depends on genetic factors, environmental conditions,
and cultural practices. Atallah [7] reported that plant analysis is a diagnostic tool for
optimum fertilization and indicated that no fertigation could be successful unless the
soil fertility status is also considered. Guidelines integrating both crop requirements
and nutrients availability are essential. Concerning the soil, the levels of major elements
and the properties are liable to change such as the salinity, pH and organic matter.
Hajrasuliha et al. [34] found that most of the N organic fertilizer for both NO 3 and
NH 4 applications was in the top 60 cm of soil where the vine roots were of greatest
density. There was no indication of signifi cant N leaching below 2.4 m or denitrifi ca-
tion of fertilizer N for the trickle irrigated vines during the growing season. Mussaddak
and Somi [63] stated that nitrogen fertilizer of cotton plant under different irrigation
methods is the key factors for yield increase and yield quality improvement. With
good management of these two factors, both production and quality can be attained
simultaneously.
20.1.4 EFFECTSOFIRRIGATION SYSTEMS ON GRAPE YIELD QUALITY
Rakhlmanina et al. [69] indicated that the juice sugar content of grapes varied between
22.3 and 23.4% under drip and furrow irrigation, respectively, and ranged from 20.6
to 22.3 in the control. Saayman and Lambrechts [71] stated that the table grapes on
grayish, sandy soil responded to irrigation applied N fertilization levels, patterns of
N application, crop load and preplant P and K fertilization. Potassium applied in this
manner was found to be ineffective due to leaching and regular irrigation-applied K
fertilization had to be adopted. Increased crop load had a marked negative effect on
shoot growth and grape quality, comparable in magnitude to that of too high N levels. A
balanced crop load of 22 bunches per vine with a shoot mass of 1822 kg was calculated
for this trial, but a crop load of 18-19 bunches per vine was maximum still ensuring
the best quality. According to Pire and Ojeda [67], different irrigation regimes affected
the overall grape fruit quality. They added that lower irrigation volumes consistently
decreased fruit acidity and plant shoot growth.
Ashcroft et al. [6] studied the effects of irrigation methods (trickle and furrow), N
and K application on fruit yield and quality of processing tomatoes were investigated
in three fi eld experiments with different cultivars (FM 785, Pacesetter and Alta), soil
types (loam, clay loam and sand). Ripe fruit yield increased with increasing N ap-
plication rate at all sites. The optimum yields were obtained at 280-300 kg of N.ha -1 .
The number of green and rotten fruits increased signifi cantly with increasing N rate
at the two trickle-irrigated sites but not at the furrow-irrigated ones. Fruit size was not
consistently affected by N or K. The TSS content increased with increasing N rate at
two of the sites. Although K alone had no signifi cant effect on TSS content, yet there
was a signifi cant N × K interaction at one site, possibly due to an osmotic effect of the