With the development of the facility vegetables, long time continuous cultivation caused
the soil physical and chemical conditions deteriorated, the plant diseases and insect pests
frequently occurred. This resulted in the yield declined and not only seriously hampered the
sustainable development of facility agricultural production, but also had the adversely effect
on the safety of agricultural products and ecological environment. In recent years, pepper
cultivation areas continued to expand because of the economic benefit. Pepper had become
one of the important facility vegetables in northwest region and also proved to be the superior
crop for increasing farmers′ income and promoting rural economic development. Mulching
were widely used in agricultural production because of its good effect, however, this study
was mainly on the field crops and also concentrated one of the mulching effect on crops. And
lacked of systematic research on the effect of various mulching practices, especially in the
greenhouse vegetable production this system was less researched. Therefore, this study was
carried out in the experimental greenhouse of Institute of the soil and water conservation, the
Chinese Academy of Science and Ministry of water Resources in Yangling in 2011 and 2012.
And the objective of the research was to study the effect of the different mulching practices
(CK, without mulching; FM, plastic film mulching; CM, combined mulch with plastic film
and wheat straw; SM, straw mulching) on the physiological characteristics and soil conditions
of hot pepper in greenhouse. And multiple objective comprehensive evaluations were
conducted with principal component analysis method and grey relational analysis method.
The following results were obtained:
(1) Mulching improved the soil environment. Soil water content (SWC) was higher under
the mulching practices than under no-mulching condition and SWC followed the order
CM>FM>SM>CK; Soil temperature had significantly difference between different treatments,
mulching had warmer effect and soil temperature was also higher under mulching than under no-mulching; Mulching increased the crop absorption of nitrogen, phosphorus and potassium
and increased the fertilizer use efficiency, which significantly improved soil environmental
quality. Soil respiration (Rs) of hot pepper was changed under mulching practices. The
highest Rs was obtained under CM treatment and the Rs measured in the control soil was
always lower than that for any mulch material treatment over the entire growing season; The
differences between CK and FM and CM and SM were significant at p<0.05; Based on the
grey correlative analysis, the result showed that soil organic matter, root vigor, soil and air
temperature were the key influencing factors under mulching practices and the relationship of
Rs and soil organic matter was most closely, pH had the lowest correlation coefficients with
Rs which was 0.707.
(2) Physiological characteristics of hot pepper were changed under mulching practices.
During the growth process of hot pepper, the leaf net photosynthesis rate was significant
difference between different treatments, being highest for CM application (15.98 umol CO 2
m -2 s -1 ), lowest for CK management (8.15 umol CO 2 m -2 s -1 ); Results indicated that the
photosynthesis-light response curves of hot pepper was appropriate to a non-rectangular
hyperbolic model, measured curve and simulated curve were consistent (Decision coefficients
were higher than 0.9); Apparent quantum efficiency was higher under CM (0.103) and FM
(0.08) than under CK (0.07) and SM (0.06); CM maintained more lower light compensation
point (LCP) and SM maintained higher light saturation point (LSP), which indicated pepper
was more adapted to low light under CM treatment while pepper was more adapted to strong
light under SM practices.
(3) Analysis of yield, water use efficiency and economic benefits of hot pepper under
mulching practices. Yield was highest under CM treatment and FM, CM, SM increase yield
by 55.76%, 160.58%, 135.58%, respectively; Economic income of pepper was highest under
CM (16.26 yuan m -2 ) while lowest under CK (6.24 yuan m -2 ); Water use efficiency was
significant difference between different treatments (p<0.05) and followed the order
CM>SM>FM>CK, which indicated CM was significantly better than other treatment in terms
of water conservation, increasing yield and income.
(4) Fruit quality of hot pepper was changed under mulching practices. Pepper fruit length
followed the order CM>FM>SM>CK, and also showed significant difference between different treatments (p<0.05); Pepper fruit diameter under FM, CM and SM was wider by
5.18%, 12.35% and 1.19% than CK management, while CM was the widest; Pepper fruit
shape index under CM was changed smallest (0.03) during the growing season, which showed
CM was better to maintain the consistency of the products; Vitamin C of pepper was highest
for FM (33.81 mg kg -1 ) while the lowest under CK (22.73 mg kg -1 ) treatment; The content of
pepper capsaicin was increased under CM and SM treatments and also showed significant
difference between CK and FM treatments; Mulching reduced the nitrate content in pepper
fruits, FM had the lowest nitrate content (29.81 mg kg -1 ).
(5) Principal component analysis method and grey relational analysis method were used
to conduct the multiple objective comprehensive evaluations. The result of comprehensive
evaluation was CM>SM>FM>CK while using principal component analysis methods, CM
got the highest score (4.21) while CK got the lowest score (1.53); the result of comprehensive
evaluation was CM>SM>CK>FM while using grey relational analysis method, the correlation
coefficients was highest under CM (0.912) while lowest under FM (0.709) treatment; CM was
got highest score and correlation coefficients under the two comprehensive evaluation
methods, indicating CM treatment could achieve pepper high-efficient, high-quality and
soil-quality production and CM should be promoted in facility and efficient agriculture.
Key words: Mulching, Greenhouse, Hot pepper, Physiological characteristics, Soil
environment, Comprehensive quality evaluation.