Modelling water and nitrogen dynamics of desalinated water and fertigation in tomato under controlled conditions
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Date
2019
Authors
Chawla, Ketan
Journal Title
Journal ISSN
Volume Title
Publisher
Punjab Agricultural University, Ludhiana
Abstract
The present research experiment was carried out to investigate the effect of two different qualities
of irrigation water namely canal (CW) and desalinated (DSW) water; and three fertigation levels viz. 100%
(F1), 80% (F2) and 60% (F3) of recommended NPK dose on tomato fruit yield, N uptake, water and nitrogen
dynamics with HYDRUS-2D model and soil properties using drip system in a sandy loam soil under poly
house conditions with four replications in a factorial randomized block design at Jodhpur Farm of PAU
Regional Station Bathinda during 2017-18 in S-W region of Punjab. The results revealed that plant height
increased progressively with advancement in the age of the crop under both water qualities and different
fertigation levels. Both the water qualities CW and DSW produced statistically similar plant height, number
of fruits per plant, average fruit weight, total dry matter production and total fruit yield of tomato. However,
the increasing fertigation level from 60% of recommended NPK dose (F3) to 100% (F1) of recommended
NPK dose significantly increased the plant height, yield components, total dry matter and fruit yield of
tomato at successive growth stages. The N content of different partitioned plant parts viz. leaves, stem and
roots decreased with each successive growth stage, irrespective of water quality and fertigation levels. Water
quality had no significant on the N content and uptake of leaves, stem and roots at successive growth stages
(120 DAT, 150 DAT, 180 DAT and at maturity). Highest fertigation rate (F1) recorded highest content and
accumulation of N in leaves, stem and roots while lowest under F3 at all growth stages. The absorption of N
by tomato leaves increased with increasing plant age upto 150 DAT whereas the total N accumulation tended
to decline at 180 DAT and maturity at all the fertigation rates in both the water qualities. Unlike tomato
leaves, the total N removal in stem and roots continued to increase at successive stages of tomato growth
upto maturity. The N content in fruits produced with both water qualities was also statistically similar but the
fertigation levels had a significant effect on the N content of fruits at 7th picking and final harvest. The effect
of water quality and fertigation levels on the pH, electrical conductivity, organic carbon content and SAR of
the soil was found to be non-significant at all the soil depths (0-15, 15-30, 30-45 and 45-60 cm). Irrigation
water quality didn’t influence the available N, NH4
+-N and NO3
--N content of the soil but fertigation levels
significantly influenced all these forms of N in soil at all the depths except for NH4
+-N and NO3
--N in 45-60
cm soil depth. The maximum available N, P and K content of the soil was recorded under F1 followed by F2
and minimum in F3. The influence of water quality and fertigation levels on sodium adsorption ratio (SAR)
and bulk density of soil was found to be non-significant in all the depths signifying the analogous effect of
desalinated (DSW) water on soil properties as that of canal water (CW). The comparison between the
observed and predicted values of water and nitrogen content in a sandy loam soil for both calibration and
simulation of HYRUS-2D had high value of R2, low value of RMSE, and high index of agreement which
showed that model was predicting the water and nitrogen content values with greater accuracy in tomato
crop under protected cultivation. These results indicated the similar effect of canal water (CW) and
desalinated water (DSW) on fruit yield of tomato and soil properties with drip system. It suggests that
desalinated irrigation water quality comparable to canal water along with 100% fertigation under drip can be
used successfully for growing of tomato on sandy loam soil under controlled environment during the initial
years of its cultivation.