Water footprint assessment of cotton-wheat cropping system in south-western Punjab
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Date
2022
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Punjab Agricultural University
Abstract
The present study entitled, “Water footprint assessment of cotton-wheat cropping system in south western Punjab” has been carried out at Punjab Agricultural University, Regional Research Station,
Faridkot in cotton during Kharif season 2021 and in wheat during Rabi season 2021-22. A field experiment having eighteen treatments was laid out in a Randomized complete block design with three
replications. Four nitrogen levels viz., 100 % (recommended dose of nitrogen @ 112.5 kg ha-1) and 125 % of RDN were fertigated in either 10 and/or 14 equal splits at 10 days interval for cotton while for wheat, 100 % of RDNP (recommended dose of nitrogen @ 125 kg ha-1 and phosphorus @ 62.5 kg ha-1) and 80% were fertigated in either 8 and/or 10 equal splits at 7 days interval. The subsurface fertigation was executed under two lateral depths [25 cm (L1) and 30 cm (L2)] and two emitter spacings [30 cm (S1) and 40 cm (S2)]. In addition, two extra control treatments including surface flood method (control 1) and existing recommendation of sub-surface drip fertigation at 20 cm lateral depth and 20 cm emitter spacing with 100 % RDN in cotton and 80 % RDNP in wheat (control 2) were also evaluated. Results revealed that in cotton-wheat cropping system, subsurface drip system established at 25 cm lateral depth along with 30 cm emitter spacing (L₁S₁F4) recorded 24.9 % higher seed cotton yield and 17.3 % higher wheat grain yield over subsurface drip system installed at 30 cm lateral depth with 40 cm emitter spacing (L2S2F4). However, in comparison to surface flood method (control 1) the existing recommendation of subsurface drip fertigation system (control 2) recorded 36.1 % higher seed cotton yield and 25.6 % better wheat grain yield. In both crops, the improved growth and yield parameters under L₁S₁F₄ were evident mainly due to favourable micro-climatic conditions like lower canopy temperature coupled with better physiological parameters such as relative water content, chlorophyll content, rate of photosynthesis and stomatal conductance. In cotton, subsurface drip fertigation of 125 % RDN with 14 splits (L1S1F₄) at 10 day interval through lateral placed at 25 cm (L₁) depth having 30 cm emitter spacing (S₁) recorded lowest water footprint (2.3 m³ kg⁻¹). The conventional cotton crop receiving surface flood irrigation and manual fertilizers broadcasting (control 1) resulted into higher water footprint (3.6 m³ kg⁻¹). Similarly, in wheat crop, sub-surface drip fertigation of 100 % RDNP into 10 splits at 7 day interval (F₄) having 25 cm laterals depth (L₁), and 30 cm emitter spacing (S₁) exhibited minimum water footprints (1.1 m³ kg⁻¹). Contrarily, reduced dose of 80 % RDNP supplied in 8 splits at 30 cm lateral depth and 40 cm emitter spacing under T13 treatment (L₂S₂F₁) resulted in higher water footprint (1.5 m³ kg⁻¹). In cotton-wheat cropping system, maximum water footprint (5.06 m³ kg⁻¹) was recorded under surface flood irrigation (control 1) however, minimum water footprint (3.38 m³ kg⁻¹) has been observed under L1S1F4. Among different treatments in cotton-wheat cropping system, total water footprint increased by 14 % in L₂ (30 cm) than L₁ (25 cm). Similarly, 7.5 % more water footprint was recorded in wider spacing (S₂=40 cm) as compared to the narrower spacing (S₁=30 cm) of emitters. A reduced water footprint to the tune of 22.1 % was evident under control 2 as compared to control 1 (surface flood method). Similarly, water footprint under F₄ was reduced by 3.2, 8.0 and 13.2 % over F₃, F₂ and F₁, respectively. Therefore, fertigation with higher splits through subsurface drip system having 25 cm lateral depth and 30 cm emitter spacing was found to be suitable for higher productivity and lower water footprints in cotton – wheat cropping system.
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Veerpal Kaur (2022). Water footprint assessment of cotton-wheat cropping system in south-western Punjab (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.