PERFORMANCE OF GRAPEVINES UNDER IRRIGATION SYSTEMS - Management, Performance, and Applications of Micro Irrigation Systems - page 254

WUE [kg fruit weight (FW) kg-1 water] was obtained in the two treatments indicating
that drip irrigation may increase the potential for control of vine growth by making
vines more dependent on irrigation and N fertilization than furrow irrigation.
Burt et al. [17] stated that irrigation was an effective means to improve WUE
through increasing crop yield, especially in semiarid and arid environments. Even in
subhumid and humid environments, irrigation is particularly effective in overcoming
short duration droughts. However, irrigation by itself may not always produce the
highest WUE possible. Masood et al. [57] stated that WUE may be improved with
some management practices such as: changing sowing time, irrigation effi ciency, bal-
anced nutrition, mulching, and tillage management. They found a negative signifi cant
correlation between WUE and irrigation requirements. Veeranna et al. [79] conducted
fi eld experiments in Bangalore, Karnataka, India, during the Rabi season of 1997 and
1998 to investigate the effects of fertigation and irrigation methods on chili cv. By-
adagi Dabba . The treatments comprised of soil application of normal fertilizers (N, P,
K applied as urea, single superphosphate and muriate of potash, respectively) at 100%
recommended dose, in combination with furrow irrigation or drip irrigation. WUE
was signifi cantly higher with drip fertigation of water soluble fertilizer (WSF) at 80%
recommended dose (2.81 kg.ha -1 .mm -1 ), which was closely followed by drip fertigation
of 100% recommended level of WSF (2.77 kg.ha -1 .mm -1 ). The two treatments were
signifi cantly superior to the rest of the treatments. Higher dry fruit yield coupled with
lower water use (450.21 and 446.80 mm at 80% and 100% recommended level of
WSF, respectively) were responsible for high WUE.
20.1.3 EFFECTS OF IRRIGATION SYSTEMS ON FERTILIZATION AND
FERTILIZER USE EFFICIENCY
Barber [11] defined fertilizer efficiency as “the amount of increase in yield of the har-
vested portion of the crop per unit of fertilizer nutrient applied where high yields are
obtained.” Many factors soil, plant, and climatic contribute to the efficiency of applied
fertilizer in croplands. In addition, the nature of fertilizer materials and the methods of
use also affect their availability. He mentioned three important soil parameters, which
are responsible for the rate of supply of nutrients from the soil to the root: diffusion
coefficient, nutrient concentration in soil solution, and buffering capacity. The diffusion
coefficient is the most important factor and its magnitude is influenced by volumetric
water percentage, the tortuosity of the diffusion path and the buffer capacity. By in-
creasing the water content of soil, a reduction in tortuosity was observed. Baligar and
Bennett [10] stated that the efficiencies of added N, P2O5 and K2O are of the order
<50%, 10%, and 40%, respectively. For enhancing efficiency of applied fertilizers, it is
essential to approach the problem on many fronts, namely: (1) increasing the efficiency
of crop plants to absorb and use the nutrients, (2) reducing or using existing fertilizer
to improve their efficiency either by rate or method of applications, (3) use of fertilizer
reaction modifiers such as nitrification and urea hydrolysis inhibitors, (4) correcting the
soil acidity or alkalinity by amendments so that crops and soil microbial populations
are at their greatest potentials, and (5) exploiting the nature of interaction of soil es-
sential elements and crop growth.