Bell Pepper

With the increasing population, land fragmentation, and rapid urbanization, land
for agriculture is continually decreasing and land-holding size is shrinking. Under
these circumstances, off-season cultivation of vegetable crops under protected
cultivation offers a viable alternative for efficiently using land and other resources.
Bell pepper (Capsicum annuum L. var. grossum Sendt.) is an important off-season
vegetable crop in North India (Prakash et al. 2003). However, low temperature and
sensitivity to frost constrain off-season bell pepper cultivation (Dıaz-Pérez ́ 2010).
Bell pepper requires 20–25°C air temperature (Wien 1997; Rubatzky and
Yamaguchi. 1999) and root zone temperature (RZT) of 21–27°C for optimal
growth, flowering, and fruit setting (Dı́
az-Pérez 2010; Ityel et al. 2014). In North
Indian plains, the outdoor crop suffers from low-temperature stress during winter
(10-year January average = 2°C) and high-temperature stress during summer (10-
year May average = 43.9°C) (Singh and Sharma 2007). For warm-season crops,
such as bell pepper, the production strategies that enhance earliness and extend

availability period may substantially increase market value of the crop are urgently
required. Thus, an improved understanding of modification of crop microclimate
through structural and agronomic interventions that improve plant growth and
yield through optimization of soil and air temperatures is critical for promoting
off-season cultivation of bell pepper in this region.
Protected cultivation is extensively used in India to provide controlled environmental conditions suitable for optimal vegetable crop production (Singh and
Sirohi 2006). Protected cultivation not only improves productivity but also
enhances the produce quality and ensures off-season availability. The economic
returns are 10 to 15 times higher under protected structures as compared with
open-field cultivation (Panda et al. 2008). Protected structures, such as polyhouses,
walk-in tunnels, and row covers, extend crop span and availability period by
safeguarding the crop from inclement weather. Further, the vegetables grown
under these structures possess better quality, reduced pesticide residue, and higher
yield than the ones grown under open-field conditions. (Hunter et al. 2012). The
concept of growing vegetables under protected structures has been gaining popularity among North Indian growers, especially those with small land holdings
(Kumar and Verma 2009). In North India, moderate to severe winter climate
offers great scope for use of low-cost, naturally ventilated polyhouses.
Mulches have been reported to increase yield by stimulating root growth
and nutrient uptake, suppressing weeds, regulating soil, and air temperature
and modifying the radiation budget (Gill and McSorley 2012; Gill, McSorley,
and Branham 2011; Tarara 2000; Wein et al., 1993). In warm environments,
however, plastic mulches may create high RZT conditions that may be detrimental to growth and yield of vegetables (Lamont 2005). Thus, choosing the
appropriate planting date(s) under the North Indian conditions is critical for
escaping late-season (May – June) high-temperature effects, particularly under
polyhouse and mulch treatments (Dhaliwal et al. 2017).
In the past, some efforts have been made to study the effects of growing
environments or cultural conditions, planting dates, and mulch treatments on
vegetative and reproductive responses of bell pepper. However, the information
on their cumulative and interactive effects is lacking. The main objective of this
study was to investigate the interactive effect of planting date and mulch treatments for bell pepper under self-ventilated polyhouse vs. open-field conditions
on plant growth and yield performance. Such information should be useful for
developing protected cultivation practices for off-season cultivation of bell
pepper under moderate to severe winter environments in North Indian plains.
Materials and methods
Location and polyhouse structure
This experiment was conducted at the Vegetable Research Farm of Punjab
Agricultural University (PAU), Ludhiana, India (30°54ʹ north latitude and

70°45ʹ east longitude). Rainfall, and maximum and minimum temperatures
of the experimental site during 2010–2011 and 2011–2012 seasons are shown
in Figure 1. The framed, naturally ventilated polyhouse structure used in the
study consisted of galvanized iron (GI) pipes covered with an ultra violet
(UV)-stabilized plastic sheet of 200 µm thickness at the top and a UVstabilized 40-mesh size net on the sides. The structure was 3.1 m high at
the center and 2.1 m on the sides.
Nursery raising, transplanting, and experimental design
Seeds of bell pepper cultivar “Indra F1” (Indo-American Hybrid Seeds, India)
were sown on 15 September, 30 September and 15 October during the
2010–2011 and 2011–2012 seasons. To ensure a good crop stand through
prevention of soil-borne, pathogen-induced wilts, experimental plots were
fumigated with 2% solution of formaldehyde applied at 5 Lm−2
. One-month
old seedlings were transplanted, 1 month later, on 15 October, 30 October, and
15 November, respectively. The experiment was conducted in a split-split-splitplot design, with two replications, where the polyhouse vs. open-field conditions
were main plots; three planting dates (15 October, 30 October, and 15
November) sub-plots; and four mulch treatments (black polythene, clear polythene, paddy straw at 6.25 t ha−1
, and no-mulch) sub-sub-plots. Black and clear
polyethylene films were made up of low-density polyethylene 1.2 m in width and
25 µm in thickness. The transplanted seedlings were grown on raised beds

(90 cm between rows and 30 cm within-row spacing) covered with mulch as per
treatments. Each treatment accommodated 16 plants in two parallel rows. The
experiment was drip-irrigated and drippers were placed 30 cm apart, with water
discharge capacity of 2.25 L h−1
. The drip tape (Jain Irrigation System Ltd.,
Jalgaon, Maharashtra, India) was buried in the center of the bed at a depth of
15 cm. Irrigation and fertigation schedules and other agronomic practices, as
recommended for the region by Punjab Agricultural University, Ludhiana (PAU
2010; Sharda et al. 2011), were followed to raise a healthy crop.
Meteorological observations
Root-zone temperature (RZT, °C) at 10 cm depth was recorded daily at 07:30 h
during January-February, the coldest months of the year, using Venus Soil Glass
Thermometer (A. Paul Instruments Co., New Delhi, India) installed in the middle
of the plots and 10 cm from the planted row, as recommended by Ibrahim and
Marlene (1995). The diurnal cycles of net radiation (NR, watts m−2
) received from
09.00 h to 17.00 h were recorded using NR2-07 Dome Net Radiometer (Delta-T
Devices Ltd, Burwell, Cambridge, UK). Morning and afternoon air temperatures
(ºC) were recorded at 07:30 h and 14.00 h, respectively.
Growth and yield
Both plant growth-related and yield-related traits were measured. Plant height
(PH, cm), fruit number plant–1 (FN), fruit weight (FW g, mean of 10 representative fruits), early yield (EY kg plant−1
, fruit harvest till March 31), marketable yield
(MY, kg plant−1
), and total yield (TY, kg plant−1
) were recorded at maturity.
Statistical analysis
The data were subjected to analysis of variance (ANOVA) using PROC GLM
statement of SAS version 9.2 (SAS Inst., Cary, N.C., USA). The data on PH,
FN, FW, EY, MY, and TY were analyzed according to a split-split-split plot
design, as described in Gomez and Gomez (1984). Treatment differences
were determined using Fisher’s protected least significant difference (LSD) at
p ≤ 0.05. p Values for all possible pairwise comparisons generated through
PDIFF option of PROC GLM were used to determine significant differences
among interaction means where the interaction was significant.
Results
Figure 2 represents net radiation (NR) as influenced by growing environments
(polyhouse vs. open-field) and mulch treatments. Overall, polyhouse received
higher amount of NR (328.3 watts m−2
) as compared with the open-field (305.8
watts m−2
) conditions; the trend was the same on all three sampling dates, i.e., 23
February, 15 March, and 25 April, 2011. Black polythene mulch absorbed comparatively higher amount of NR, followed by clear polythene, paddy straw and no