Crop rotation and tillage management options for sustainable intensification of rice-fallow agro-ecosystem in eastern India

Abstract

Presently, rice-fallows are targeted for cropping intensification in South Asia. Rice-fallows a rainfed mono-cropping system remain fallow after rice due to lack of irrigation facilities and poor socio-economic condition of the farmers. Nevertheless, there is the scope of including ecologically adaptable winter crops in water-limited rice-fallow conditions with effective moisture conservation practices. The study aimed to identify the winter-crops that are adaptable and productive in rice-fallow conditions and to evaluate the different tillage-based crop establishment practices for soil moisture conservation, grain yield, economics, and sustainability parameters. Six different crop establishment and residue management (CERM) practices viz., zero-tillage direct seeded rice (ZTDSR), zero-tillage transplanted rice (ZTTPR), puddled transplanted rice (PTR), ZTDSR with rice residue retention (ZTDSR_R+), ZTTPR with rice residue retention (ZTTPR_R+), PTR with rice residue retention (PTR_R+) as main-plot treatment and five winter crops (chickpea, lentil, safflower, linseed, and mustard) as sub-plot treatment were evaluated in a split-plot design. The productivity of grain legumes (chickpea and lentil) was higher over oilseed crops in rice-fallow conditions with an order of chickpea > lentil > safflower > mustard > linseed. Among the CERM practices, ZTDSR_R+ and ZTDSR treatments increased the grain yield of all the winter crops over PTR treatment, which was primarily attributed to higher soil moisture retention for an extended period. Grain yield increment with conservation tillage practices was highly prominent in safflower (190%) followed by lentil (93%) and chickpea (70%). Rice grain yield was higher (7-35%) under PTR treatment followed by ZTDSR treatment. Conservation tillage practices (ZTDSR, ZTTPR) reduced energy use (11-20%) and increased the energy ratio over conventional tillage practice (PTR), higher in rice-safflower, rice-lentil and rice-chickpea rotations. Higher net return was attained in rice-safflower and rice-chickpea rotations with ZTDSR_R+ treatment. Predicted emission of greenhouse gases was markedly reduced in ZTDSR treatment (30%) compared to ZTTPR and PTR treatments. Hence, the study suggests that cropping intensification of rice-fallows with the inclusion of winter crops like chickpea, lentil, and safflower following conservation tillage practices (ZTDSR_R+ in particular) could be the strategic options for achieving the higher system productivity, economic returns, and energy use efficiency with the reduced emission of greenhouse gases.

Figure 1

Effective tiller, panicle length, and grains panicle⁻¹ of rice as influenced by different tillage based crop establishment practices. Error bar indicates standard error of mean. Different lowercase letters correspond to treatments are significantly different at p < 0.05 by Duncan’s multiple range test.

Figure 2

Field view of soil cracks under different tillage cum crop establishment practices (a–c). Crack width (d), depth (e) and volume (f) as influenced by different tillage cum crop establishment practices (2-year mean). Error bar represents the standard error of mean; Different lowercase letters correspond to treatments are significantly different at p < 0.05 by Duncan’s multiple range test.

Figure 3

Soil moisture content (w/w) under different tillage and residue management treatments during 2016–2017 and 2017–2018; *significantly different at p < 0.05; ‘ns’ non-significant.

Figure 4

Soil moisture depletion from soil profile (0–30 cm) under different tillage and residue management practices. Error bar indicates standard error of mean. Different lowercase letters correspond to treatments are significantly different at p < 0.05 by Duncan’s multiple range test.

Figure 5

Emission of N₂O and global warming potential (GWP) of N₂O as influenced by different crop rotations in rice-fallow (2-year mean).

Figure 6

Scatter plot of treatments [CERM × WC] on PCA coordinates. R-C: rice-chickpea; R-L: rice-lentil; R-SF rice-safflower; R-Li: rice-linseed; R-M: rice-mustard. SREY: system rice equivalent yield; WCGY: winter crop grain yield, SNR: system net returns; SBCR: system benefit cost ratio; SEI: system energy input; SNEO: system net energy output; SWUE: system water use efficiency.