Intercropping and mulching in rain-dependent cotton can improve soil structure and reduce erosion

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This study pointed out that growing an intercrop and retaining its residues as in situ mulch between the cotton rows can improve soil condition by increasing soil microstructure, water stable aggregation and infiltration rate, and reducing run-off and soil loss.

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Nội dung Text: Intercropping and mulching in rain-dependent cotton can improve soil structure and reduce erosion

Environmental Advances 4 (2021) 100068 Contents lists available at ScienceDirect Environmental Advances journal homepage: www.elsevier.com/locate/envadv Intercropping and mulching in rain-dependent cotton can improve soil structure and reduce erosion Desouza Blaise a,∗, A. Manikandan a,b, N.D. Desouza c, B. Bhargavi a, J. Somasundaram d a ICAR-Central Institute for Cotton Research, Nagpur, 441108, Maharashtra, India b ICAR-Indian Agricultural Research Institute, Pusa, New Delhi, 110012, India c Department of Physics, Visvesvarayya National Institute of Technology, Nagpur, 440010, Maharashtra, India d ICAR-Indian Institute of Soil Science, Nabi Bagh, Berasia Road, Bhopal, 462038, Madhya Pradesh, India a r t i c l e i n f o a b s t r a c t Keywords: Transgenic Bt (Bacillus thuringiensis) cotton (Gossypium spp.) hybrids are grown at wide-row spacing in India. Clay soils Farmers practice traditional methods of cultivation that involve excessive inter-row cultivations. These practices Electron microscopy exacerbate soil erosion and run-oﬀ ultimately leading to land degradation. Growing a cover crop between the Inﬁltration rate cotton rows and retaining its residues in situ can reduce erosion and runoﬀ, and improve soil productivity. We Plastic mulch compared the eﬀects of growing an intercrop {sorghum (Sorghum bicolor), sunnhemp (Crotolaria juncea) or sesame Sunnhemp Transgenic cotton (Sesamum indicum)} in between the cotton rows and retaining its residues as in situ mulch, vis-à-vis plastic, Vertisols newspaper mulch and the traditional farmers’ practice (FP) on the soil physical properties (soil microstructure, porosity, water stable aggregates, inﬁltration rate, soil erosion and soil loss) of a Vertisol near Nagpur in central India. Digital image analysis of the micrographs obtained by a scanning electron microscope indicated porosities were highest with intercropping (53–58%) and the least with the FP and plastic mulching (35–36%). Inﬁltration rate was in the order of intercropping (19.4–22.6 mm h−1 ) > newspaper mulch (14.5 mm h−1 ) > FP (13.8 mm h−1 ) > plastic mulch (12.3 mm h−1 ); while the reverse occurred with respect to run-oﬀ. Although run-oﬀ was the greatest (577 mm) in the plastic mulched plots, soil loss was negligible (0.58 Mg ha−1 ). Intercropping resulted in 35% less soil loss than FP (6.7 Mg ha−1 ). This study pointed out that growing an intercrop and retaining its residues as in situ mulch between the cotton rows can improve soil condition by increasing soil microstructure, water stable aggregation and inﬁltration rate, and reducing run-oﬀ and soil loss. 1. Introduction tic and geotextiles are reported to reduce soil erosion, overcome water stress caused by dry spells during the rainy season and improve soil Cotton (Gossypium hirsutum L.) is the major commercial crop in In- organic carbon concentration (Gimenez-Morera et al., 2010; Lal, 2015; dia grown on more than 12 million hectares and more than 90% of Zhao et al., 2019). Organic materials as mulch are also known to im- the area is occupied by the transgenic Bt (Bacillus thuringiensis) Boll- prove soil physical and chemical properties (Lal, 2015). Because trans- gardII® (BGII) cotton hybrids (Blaise et al., 2014). Most of the area genic cotton hybrids are grown at wide inter-row spacing (0.90 to is rain-dependent and farmers practice intensive and frequent tillage 1.2 m), it is possible to sow an intercrop between the rows (Blaise et al., operations to control the weeds in between the cotton rows that are 2014; Rajpoot et al., 2018). The beneﬁts include better weed control, planted at wide-row spacing (Blaise and Ravindran, 2003). Frequent and higher seed cotton yield and proﬁtability (Blaise et al., 2020). It has tillage on a long-term basis with very limited manure application been speculated that because the intercrops are cut and left as mulch, (Prasad and Power, 1991) can result in soil structural degradation it returns crop residue to the soil and improves soil quality more than (Bhattacharyya et al., 2015). Poor soil structure in combination with that under traditional farmers’ practice (FP) or plastic mulch. However, heavy rains received during the rainy season causes accelerated ero- there are no data to support such assumptions. We hypothesized that sion of topsoil leading to a decline in soil organic matter and nutrients in comparison with the FP, soil structure improved by sowing an inter- (Singh et al., 2020). crop between the rows of transgenic cotton. The objective of our study Alternative tillage practices and cropping systems such as mini- was to quantify soil physical properties and soil loss with several inter- mum and no tillage, and mulching with retained crop residues, plas- row management practices at the end of a long-term (2013-14 to 2019- 20) ﬁeld experiment conducted on a rainfed Vertisol in central India (Blaise et al., 2020). Physical properties assessed were microstructure ∗ Corresponding author. (pore shape and pore orientation) measured with a scanning electron mi- E-mail address: blaise_123@rediﬀmail.com (D. Blaise). croscope, water stable aggregation and inﬁltration capacity. Pore shape https://doi.org/10.1016/j.envadv.2021.100068 Received 28 October 2020; Received in revised form 21 April 2021; Accepted 13 May 2021 2666-7657/© 2021 Indian Council of Agricultural Research. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
D. Blaise, A. Manikandan, N.D. Desouza et al. Environmental Advances 4 (2021) 100068 and orientation are direct indicators of the structural state of the soil and sieved so that their natural structure remained intact. Subsample (Romaneko et al., 2019) and inﬂuence processes such as water inﬁltra- of the air-dried soil was coated with gold-palladium mixture by sputter tion, runoﬀ and erosion (Sokolowska et al., 2019). coating technique prior to the analysis. Microstructure analysis was performed using JEOL JSM 6380 scanning electron microscope, SEM 2. Materials and methods (http://www.speciation.net/Database/Instruments/JEOL/JSM6380- ;i18) that allowed visualization of the soil morphology and spatial 2.1. Study site arrangement, viz. number of pores, porosity, pore perimeter, shape factor and fractal dimension. The SEM was equipped with an energy Field experiments were conducted during 2013-14 to 2019-20 at In- dispersive X-ray spectrometer (EDS) coupled with a Bruker detector dian Council of Agricultural Research-Central Institute for Cotton Re- SDD X-Flash (Schrader et al., 2007). The analysis of the scanning search, Panjri Farm, south of Nagpur (21° 04′ 71′′ N and 79° 04′ 40′′ E) electron micrographs was done using the Pores and Cracks Analysis in central India. The region has a monomodal rainfall pattern (June to System (PCAS) software - pore and crack analysis software developed September), with mean annual rainfall of 1064.1 mm (Government of by (Liu et al., 2011). Maharashtra, 2021). Total annual rainfall received was 960 and 1108 mm, respectively, in 2018 and 2019. Surface soil samples were collected 2.4. Water stable aggregates from the study site, before the start of the experiment, from three ran- dom locations, air-dried, and ground to pass a 0.5 mm sieve followed by Water stable aggregates was determined on pre-moistened 4 g soil analysis. The soil is a deep black Vertisol belonging to the Typic Chro- samples (aggregate diameters
D. Blaise, A. Manikandan, N.D. Desouza et al. Environmental Advances 4 (2021) 100068 Fig. 1. SEM image of the soil samples from diﬀerent treatments: (a) sorghum; (b) sunnhemp; (c) sesame; (d) polythene mulch; (e) newspaper mulch; and (f) farmers’ practice. Table 1 Inﬂuence of the diﬀerent treatments on the soil and pore parameters obtained by PCAS. Sorghum Sunnhemp Sesame Polythene Newspaper Farmers’ Practice Number of pores 355 458 294 223 257 304 Porosity (%) 52.9 54.2 58.1 35.2 48.6 36.0 Perimeter 253.5 224.6 242.4 270.9 321.2 254.5 Average shape factor 0.348 0.364 0.359 0.301 0.316 0.324 Fractal dimension 1.584 1.558 1.556 1.403 1.566 1.393 and compact. Speciﬁcally, porosity was greater with intercropping (53 ter ranged from 225 to 321 μm with highest values occurring with the to 58%) than with plastic or newspaper mulch, or FP (35 to 49%) newspaper mulch followed by the plastic mulch and FP. On average, the (Table 1). Among the intercrops, porosity was in the order of sesame > intercropped plots had lower values. The shape factor values occurred sunnhemp > sorghum, and the maximum number of pores in the order in a narrow range of 0.301 to 0.364 with the highest values present with of sunnhemp > sorghum > sesame. The pores were of two main types, intercropping and lowest with the plastic mulch. Fractal dimension val- mesopores (10–50 nm) and macropores (>50 nm). Numbers of micro- ues (Table 1) denote the shape irregularities and the changes brought pores were negligible whereas macropores accounted for the greatest about by the intercrops and the mulching relative to the FP. The values proportion in all treatments. Plastic mulching had the fewest number of the fractal dimension ranged from 1.39 to 1.58, and were lower with of pores which was similar to that of the newspaper mulch followed the plastic mulch and FP than with intercropping. FP had the lowest by the sesame intercrop and FP. Average values of the pore perime- values and sorghum intercropping the highest. 3
D. Blaise, A. Manikandan, N.D. Desouza et al. Environmental Advances 4 (2021) 100068 Table 2 Water stable aggregates, Inﬁltration rate, rain water run-oﬀ and potential soil loss in the diﬀerent treatments. Water stable aggregates (%) Inﬁltration rate (mm h−1 ) Rain water run-oﬀ (mm) Potential soil loss (Mg ha−1 ) Sorghum 65.8 21.1 337.8 4.39 Sunnhemp 66.9 19.4 366.7 4.57 Sesame 68.4 22.6 314.8 4.09 Plastic mulch 63.5 12.3 577.0 0.58 Newspaper mulch 64.4 14.5 492.5 5.10 FP 62.5 13.8 515.1 6.70 LSD (p > 0.05) 3.6 2.42 - - 3.2. Water stable aggregation Intercropped plots had higher porosities and more pores per unit area. Greater porosity may have been due to one or more of the follow- Data presented in the Table 2 indicates that the water stable aggrega- ing processes: (a) reduction in foot and vehicular traﬃc (Adimassu et al., tion was aﬀected by the diﬀerent treatments. Intercrop treatments had 2019); (b) addition of organic matter by the decomposing surface mulch 6.7% greater percent water stable aggregates than with FP (Table 2). placed on the soil (Mikutta et al., 2006); (c) creation of biopores by Among the intercrops, treatment diﬀerences were not signiﬁcant. Sig- growing intercrop roots (Stirzaker et al., 1996); (d) stimulation of soil niﬁcantly (p > 0.03) greater aggregation was observed with sesame in- fauna and microﬂora activity by the mulch, thereby enhancing soil tercrop than the FP, plastic and newspaper mulch. Water stable aggre- porosity (Lee and Foster, 1991; Valdez et al., 2020). In addition, the gate values of the FP treatment were similar to plastic and newspaper roots may have stimulated microbial activity, which in turn enhanced mulched treatments. stabilization of soil organic matter and improved porosity (Liang et al., 2017). Furthermore, due to the absence of subsequent soil disturbance in the intercropped plots pore continuity may have been maintained over 3.3. Inﬁltration rate the seasons (Hulugalle et al., 1997), whereas with FP frequent inter-row cultivation occurred. As a result, soil structure was disrupted, and poros- In general, steady state inﬁltration rate was greater with intercrop- ity and pore number decreased. Pore numbers and porosities were low ping (Table 2). Among the intercropped treatments, inﬁltration rate was with plastic and newspaper mulch, even though the soil surface was pro- the highest in the sesame plots and was signiﬁcantly greater than the tected. Traﬃc associated with the replacement of plastic and newspaper sunnhemp but did not diﬀer with sorghum. All the intercropped plots mulch every season may have caused compaction and low porosity. In had signiﬁcantly greater inﬁltration rate than the plastic and newspaper addition, tiny microscopic fragments of plastic and newspaper remain- mulch and FP treatments. Average inﬁltration rate with intercropping ing at the end of the season may have blocked the soil pores. was 21.0 mm h−1 and was 30% higher than that with FP. Lowest inﬁl- The improvements in soil microstructure and water-stable aggrega- tration rate occurred with plastic mulching, followed in turn by FP and tion with intercropping were likely responsible for the high inﬁltra- newspaper mulching; but these diﬀerences were not signiﬁcant. tion rate (Table 2). Retention of mulch on the surface may have also prevented detachment of soil particles during high intensity rainfall 3.4. Runoﬀ and soil loss (Prosdocimi et al., 2016). Consequently, more water inﬁltrated into the soil and soil loss was reduced with intercropping. Our estimates Rainfall lost as surface runoﬀ was in the order of plastic mulching > of soil loss in the diﬀerent treatments were similar to those reported FP > newspaper mulch >intercropping (Table 2). Average runoﬀ with for soybean-based systems in a Vertisol from central India (Singh et al., intercropping was of the order of 340 mm and was 55% less than that 2020). Our ﬁndings also concur with many previous studies that re- in treatments without an intercrop. Among the intercropped treatments, ported reductions in soil loss with straw mulch (Adekalu et al., 2007; runoﬀ was least with sesame, followed by sorghum and sunnhemp. Soil Bhatt and Khera, 2006). loss ranged from 0.58 to 6.7 Mg ha−1 , and was lowest with plastic Although soil loss was negligible with plastic mulching, much of the mulching. Greatest soil loss occurred with FP followed by that in news- eﬀective rainfall received at high intensity was lost as surface run-oﬀ paper mulched plots. Among intercropped plots, soil loss was in the or- because of the impervious nature of the plastic. When compared with der of sesame < sorghum < sunnhemp. Averaged across intercropping the plastic, newspaper mulch disintegrated into smaller particles fol- treatments, soil loss in intercropped plots was 35 ± 2.5% less than that lowing heavy storm events, and was thus, less eﬀective in reducing soil with FP. loss. As expected, FP was the most vulnerable to soil erosion because it had no soil cover, lower soil porosity and fewer water stable aggregates. Furthermore, soil disturbance associated with frequent inter-row culti- 4. Discussion vation for weed control resulted in excessive loosening of the topsoil. Porosity refers to the proportion of voids within a given soil. Those with porosities greater than 40% are considered porous whereas form 5. Conclusions factor values (range from 0 to 1, with 1 corresponding to a perfect circle) describe pore shape (Anovitz and Cole, 2015). Values in the present Our studies, for the ﬁrst time, demonstrated the improvements in study were less than 0.4 indicating irregularities in pore shapes. From soil microstructure of the rain-dependent cotton grown on the Vertisols the data in Table 1, it is evident that the two treatments that had the by intercropping sorghum, sesame or sunnhemp between the rows of lowest porosities were FP and plastic mulching. Both had form factor cotton compared with the local farmers’ practice and plastic and news- values
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