The Temporal-Spatial Distribution of Light Intensity in Maize and Soybean Intercropping Systems

Transcription

1 June, 212 Journal of Resources and Ecology Vol.3 No.2 J. Resour. Ecol (2) DOI:1.5814/j.issn x The Temporal-Spatial Distribution of Light Intensity in Maize and Soybean Intercropping Systems Report HE Hanming, YANG Lei, ZHAO Lihua, WU Han, FAN Liming, XIE Yong, ZHU Youyong and LI Chengyun* Key Laboratory of the Ministry of Education for Agro-Biodiversity and Pest Management, Yunnan Agricultural University, Kunming 6521, China Abstract: Intercropping can improve field microclimates, decrease the incidence of crop diseases, and increase crop yields, but the reasons for this remain unknown. Solar radiation is the most important environmental influence. To understand the mechanisms of intercropping we established an experiment consisting of three cropping patterns: a monocropping control (treatment A) and two intercropping treatments (B: two rows of maize and two rows of soybean intercropping; C: two rows of maize and four rows of soybean intercropping). Results show that compared to monocropping, intercropping increased the amount of light penetrating to inferior leaves in maize plants. Light intensity reaching maize plants at the heading stage in intercropping increased over two-fold at 3 cm above ground and 1-fold at 7 cm above ground, compared with monocropping. At the flowering to maturity stage, light intensity at 11, 16 and 21 cm above ground among maize plants was greatly increased in intercropping compared with monocropping, by some five-fold, two-fold and 12%, respectively. Moreover, light intensity declined more slowly at the measured heights in the intercropping system compared with monocropping. From the 7 18 th leaf, light intensity per leaf increased two-fold in intercropping compared with monocropping. Daily light duration increased more than a mean of 5 h per day per leaf in intercropping compared with monocropping. The biological characters of maize including thousand kernel weight, yield per plant and area of ear leaves were all greater in intercropping than monocropping. These results suggest that, for maize, intercropping improves light density and duration significantly and this may contribute to biomass and yield increases. Key words: intercropping; maize plants; light intensity; duration time; biological characters 1 Introduction Intercropping is a traditional planting technique and is especially common in Asia and Africa. Intercropping of maize and soybean is known as a facilitative system, but underlying mechanisms remain unknown, both underground and aboveground. Intercropping can more effectively use limited agricultural resources, including solar radiation, fertilizers, water, gas and heat (Willey 199; Zhu et al. 2; Li et al. 29). There is usually a positive correlation between plant dry matter production and the amount of radiation intercepted by crops in both sole cropping and intercropping systems (Shibles et al. 1966; Monteith 1977; Natarajan et al. 198; Sivakumar et al. 1984). Therefore, the temporalspatial distribution of light intensity of the crop canopy may be the key to the production of photosynthesis and crop yield. Some research indicates that light intensity and the photosynthetically active radiation (PAR) intercepted by the upper, middle and under part of the crop canopy in glutinous and hybrid rice intercropping patterns is above that in sole cropping pattern (Zhu et al. 27). In the wheat and winter pea intercrop, better light use up to 1% was one of main causes for the advantages of intercropping in low N conditions (Bedoussac et al. 21). In relay intercrops of wheat and cotton, high productivity compared to monocultures can be fully explained by the increase in accumulated light interception per unit of cultivated area (Zhang et al. 28). Maize and other short stalk intercropping are often cultivated because of their advantages. In maize and bean intercropping, the fraction of radiation intercepted was higher and intercropping had more efficient radiation harvests than sole cropping (Tsubo et al. 21). Maize/soybean and maize/pigeon pea intercropping Received: Accepted: Foundation: this work was supported by the National Basic Research Program (211CB14). * Corresponding author: LI Chengyun. licheng_yun@163.com.

2 17 resulted in a greater land equivalent ratio (LER) and higher economic returns as compared to monoculture at all seed rates of soybean (Hayder et al. 23; Dasbak et al. 29). A maize and peanut intercropping system helps to increase production through the efficient utilisation of solar energy (Awal et al. 26). Previous studies show that intercropping can increase overall light use efficiency and yield. However, the light intensity and duration reaching a maize canopy under an intercropping or monocropping is rarely reported. It is important to quantify the radiation energy in intercropping compared with monocropping to analyze the benefits to maize and any effect on yield. The temporal-spatial distribution of light intensity indicates the spatial change and daily change in light intensity among crop plants. We conducted field experiments and compared the temporal-spatial distribution of light intensity in maize and soybean intercropping to maize sole cropping. Our data will help us understand how and to what extent intercropping improves the light condition among maize plants. 2 Materials and methods 2.1 Materials Field experiments were conducted at the Yunnan Agricultural University farm, Yunnan, China (25 7 N, E; 1916 m a.s.l ) from 6 May 29 to 22 October 29. Crop varieties used in the experiment were maize (Yunrui 88) and soybean (Nandou 12); both varieties are widely used in Yunnan. Maize and soybean seeds were simultaneously sown in north-south orientated rows. Three cropping treatments were prepared. was maize monocropping (row distance 4 cm). was two maize rows (row distance 5 cm) and two soybean rows (row distance 5 cm) intercropping (2:2). The distance from maize to the nearest soybean row was 5 cm. comprised two maize rows (row distance 35 cm) and four soybean rows (row distance 3 cm) (2:4). The distance from maize to the nearest soybean row was 4 cm. For all treatments the distance between maize plants was 2 cm and distances between soybean plants was 3 cm. Experiments were repeated three times, using a two-factor completely randomized block design. Each unit size was 4 m x 5 m. Full irrigation and fertilizers treatments were applied to each cropping system. 2.2 Method A HOBO U12-12 data-logger was placed beside maize plants. The measurement range was 1 3 footcandles (lumens ft -2 ). Light intensity >3 footcandles was recorded as the maximum value. Studies focused mostly on the upper, middle and bottom part of maize plants, where light intensity was usually in the measurement range. A Li- 64 portable photosynthesis meter was used to measure the photosynthetic rate of maize leaves. Light intensity was mainly measured at two stages: Journal of Resources and Ecology Vol.3 No.2, 212 (i) light intensity in the maize canopy was measured at 3 and 7 cm above ground at the heading stage; and (ii) light intensity at four positions in the maize canopy (11, 16, 21 and 26 cm above ground) was measured at the flowering to maturity stage. The HOBO logger recorded data every 3 min from 8: 18: in the heading stage and the flowering to maturity stage. These data were used to calculate daily mean light intensity. The experimental field was partially shadowed by trees, so only one replication included three treatments was selected. Logger location was changed daily to ensure experimental reliability. Biological characters of maize including thousand kernel weight, yield per plant and area of ear leaves were measured after harvest. This research was focused on maize only, characters and yield of soybean were ignored. 3 Results and discussion 3.1 The effect of intercropping on light intensity at 3 and 7 cm above ground during the heading stage The daily mean light intensity 3 cm above ground in the maize canopy is reported in Fig.1a. This indicates that with increasing stem height for maize and soybean, there was a trend of decreasing light intensity. From 4 19 July 29 light intensity in the intercropping plot was about threefold higher than for monocropping, possibly because our observation points were near the top of the soybean canopy, (a) Light intensity chang at 3cm above-ground among maize plants in monocropping and intercropping from 4 28 July, Jul Jul-6 Jul-8 Jul-1 Jul-12 Jul-14 Jul-16 Fig.1 Light intensity at 3 and 7 cm above ground in maize plants in monocropping and intercropping systems at the heading stage. Jul-18 Jul-2 Jul-22 Jul-24 Jul-26 (b) Light intensity chang at 7cm above-ground among maize plants in monocropping and intercropping from Aug., 29 Aug-14 Aug-15 Aug-16 Aug-17 Aug-18 Aug-19 Aug-2 Aug-21 Aug-22 Aug-23 Jul-28 Aug-24

3 HE Hanming, et al.: The Temporal-Spatial Distribution of Light Intensity in Maize and Soybean Intercropping Systems 171 and the light reaching maize was slightly shadowed. From 2 28 July 29, increasing plant height for soybean and maize meant that light intensity in the intercropping and monocropping systems decreased and then stabilized. Fig.1b indicates that on August 29, very low light intensity at 7 cm was observed in the monocropping system, below the light compensation point (14 foot candles). However, for intercropping, light intensity was about 1-fold higher than for monocropping, especially during sunny days (14 16 August, 22 August and 24 August); less difference was found for cloudy days (17 21 August, 23 August). There were no evident differences in light intensity between treatments B and C. This shows that light radiation was greater at 3 and 7 cm positions for maize plant undergoing intercropping compared to monocropping at the heading stage, especially on clear days. 3.2 The temporal-spatial distribution of light intensity during the flowering to maturity stage Fig. 2a and 2b show that light intensity was high on clear sunny days (31 August to 2 September and 7 9 September) and was low on cloudy days (i.e. 3 6 September) in both monocropping and intercropping C. On both clear and cloudy days, light intensity at 11 and 16 cm height in monocropping was always below 2 footcandles. At 11 (a) The spacial distribution of light intensity among maize plant in monocropping Aug-31 Sep-1 Sep-2 Sep-3 26cm 21cm 16cm 11cm Fig. 2 The spatial distribution of light intensity among maize plants in monocropping and intercropping C at the flowering to maturity stage. Sep-4 Sep-5 Sep-6 Sep-7 Sep-8 (b) The spacial distribution of light intensity among maize plant in intercropping (treatment C) 26cm 12 21cm Aug-31 Sep-1 Sep-2 Sep-3 Sep-4 16cm 11cm Sep-5 Sep-6 Sep-7 Sep-8 Sep-9 Sep-9 cm height, light intensity was always below 1 footcandles and lower than light compensation points. At 21 cm, light intensity in monocropping was ~3 6 footcandles, and light intensity in intercropping C was ~4 8 footcandles. However, at 26 cm height, the differences of light intensity were small between intercropping and monocropping, because the two measurement positions were on the top of the maize canopy. Therefore, it could be inferred that the difference between intercropping and monocropping was mainly found at the positions under 21 cm height. Furthermore, light intensity in the maize canopy was much higher in intercropping than in monocropping on clear sunny days. 3.3 The spatial distribution of light intensity in the crop canopy Fig. 3a and 3b illustrate that vertical patterns of light intensity in the maize canopy were similar. This applied to both clear and cloudy days and in monocropping and intercropping systems. Thus, the lower the vertical height, the weaker the light intensity. The relationship between light intensity and vertical height was approximately linear in monocropping, which indicates that the decrease in light intensity as height declined was relatively rapid in the monocropping system. However, in intercropping the relationship between them was approximately exponential, which may indicate that decreased light intensity with decreased height was relatively gentle. This trend was more obvious on clear than cloudy days. Accordingly, light intensity reduced much slower with decreased vertical height in intercropping than for monocropping. (a) Light intensity on different vertical height of maize plant on clear days R 2 =.76, P = Height (cm) R 2 =.93, P =.3 (b) Light intensity on different vertical height of maize plant on cloudy days R 2 =.81, P = R 2 =.93, P = Height (cm) Fig. 3 Relationship between light intensity in maize plants and height above ground in monocropping and intercropping systems.

4 172 (a) Daily mean light intersity of the 7 18 th leaves in monocropping and intercropping on clear days th 17 th 16 th 15 th 14 th Time Fig. 4 Daily variation in light intensity among maize plants for different leaves in monocropping and intercropping. 3.4 Light intensity distribution of the 7 18 th leaves Light intensity data at 3, 7, 11, 16, 21 and 26 cm above ground in both monocropping and intercropping systems were subject to regression analysis. According to the height of leaves, the light intensity of most maize leaves was calculated. Fig. 4a illustrates the difference in light intensity of the 7 18 th leaves height of maize plant for monocropping and intercropping. In intercropping, light intensities of the 7 18 th leaves positions were greater than the light compensation point. In monocropping, only light intensities of the th leaves positions were greater than the light compensation point, and that of the 7 13 th leaves were below this. Ear leaves (the 12 th leaf, 11 cm height) are essential for grain production, where light intensity were all below the light compensation point in monocropping, but >5 footcandles in intercropping (five-fold that in monocropping). Moreover, light intensity of the th leaves in intercropping was 5 8 footcandles, about three-fold that of monocropping. The light intensity of the 7 11 th leaves in monocropping was much less than the light compensation point in intercropping. However, the values all reached 4 footcandles, some eight-fold that of monocropping. Accordingly, it can be concluded that light Leaf 13 th 12 th 11 th 1 th 9 th 8 th 7 th (b) Daily Light intensity of the 7 18 th leaves in monocropping and intercropping C on clear days 18th 16th 14th 8: 1: 12: 14: 16: 18: 5 8: 1: 12: 14: 16: 18: th 1th 8th 15 2 Leaves Journal of Resources and Ecology Vol.3 No.2, 212 intensity among the maize plant of the 7 18 th leaves position in intercropping was much higher than for monocropping. The duration of light intensity is also important for photosynthesis. Fig. 4b shows the light intensity change of the maize canopy in monocropping and intercropping on a whole clear day. Light intensities of the 7 15 th leaves in monocropping were all <5 footcandles, but in intercropping the duration of light intensity >5 footcandles of the 9 12 th leaves reached 2, 2.5, 3 and 4 h, respectively. Furthermore, the duration of light intensity >1 footcandles of the th leaves, reached 2, 3 and 3 h, respectively. Table 1 indicates that the time of effective radiation (viz. above the light compensation point) on the position of most maize leaves in intercropping was longer than for monocropping, especially from the bottom to middle part of the maize plant. Light intensity on the position from the 7 12 th leaf in monocropping was consistently below the light compensation point. However, in intercropping the duration of light intensity above the light compensation point reached h. The duration of light intensity above the light compensation point from the th leaves in monocropping was 3, 5.5 and 8 h respectively; but in intercropping all reached 1 hours. For the th leaves height on maize plants, the difference in the duration of light intensity above the light compensation point between monocropping and intercropping was not evident. Therefore, compared to monocropping the duration of effective radiation from the middle to top position of the maize plant in intercropping had a definite advantage. 3.5 Comparing the biological characters of maize for monocropping and intercropping Table 2 indicates that maize yield characters in intercropping, including thousand kernel weight, yield per plant, and area of ear leaves are greater than for maize monocropped. The thousand kernel weight showed treatment C> treatment B > treatment A; yield per plant showed treatment B > treatment C > treatment A; and the area of ear leaves was B > treatment C > treatment A. From the trial results it was seem that the biological characters of maize were improved under an intercropping system. Table 2 Biological characters of maize in monocropping and intercropping. Thousand kernel weight (g) Yield per plant (g) Ear leaf area (cm 2 ) Table 1 Duration (h) of light intensity above the light compensation point for the 7 18 th maize leaves height in monocropping and intercropping. Leaves 18 th 17 th 16 th 15 th 14 th 13 th 12 th 11 th 1 th 9 th 8 th 7 th Monocropping Intercropping

5 HE Hanming, et al.: The Temporal-Spatial Distribution of Light Intensity in Maize and Soybean Intercropping Systems Conclusions Light is the most important energy source for plant photosynthesis. Light intensity and distribution at different heights directly affect leaf photosynthate. Our study shows that compared with monocropping, the light intercepted in intercropping systems differs in several aspects. (1) Light intensity at 3 cm above ground (while the maize was at the small bell stage) and 7 cm (near the top of the soybean plant) for maize plants intercropped was much higher than for monocropping. Light intensity increased approximately two-fold and 1-fold, respectively, on clear days. (2) Light intensity under an intercropping system was much higher at 11, 16 and 21 cm for maize plants and increased about five-fold, two-fold and 12%, respectively. The relative increase was greater on sunny days than cloudy days. With decreasing maize plant height, light intensity decreased more gently in the intercropping treatment than monocropping control. (3) From leaves 7 18 th, greater light intensity reached maize plants in intercropping than monocropping. This increased nearly two-fold for every leaf. Light duration was longer, by a mean of 5 h per day in intercropping compared with monocropping. (4) The yield components of maize including thousand kernel weight, yield per plant and leaf area were greater in the intercropping treatment than monocropping one. This study suggests that light conditions for maize were improved greatly in maize-soybean intercropping systems, which may contribute to biomass and yield directly. Mechanisms of intercropping are very complex, including crop-crop interaction, crop-microbe interaction underground, and crop-climate interaction aboveground. Many factors lead to light interception, when intercropping changes the crop cultivation structure and population structure. To understand the contribution of light to the development and growth of both maize and soybean, future studies should measure more points to fully realize the light distribution among maize plants. In addition, some principles of light change may be quantitatively identified by combing modeling and data, measuring biomass, disease resistance, and yield performance under strictly controlled conditions of light density and duration. These additional measures and controls are necessary to understand the effective use of light resources in intercropping systems. References Awal M A, H Koshi, T Ikeda. 26. Radiation interception and use by maize/peanut intercrop canopy. Agricultural and Forest Meteorology, 139: Bedoussac L, E Justes. 21. Dynamic analysis of competition and complementarity for light and N use to understand the yield and the protein content of a durum wheat winter pea intercrop. Plant and Soil, 33(1-2): Dasbak M A D, J E Asiegbu. 29. Performance of pigeon pea genotypes intercropped with maize under humid tropical ultisol conditions. Journal of Animal & Plant Sciences, 4(2): Hayder G, S S Mumtaz et al. 23. Maize and soybean intercropping under various levels of soybean seed rates. Asian Journal of Plant Sciences, 2(3): Li C Y, He X H, et al. 29. Crop Diversity for Yield Increase. PLoS ONE, 4(11): e849. doi:1.1371/journal. Pone.849 Monteith J L Climate and the efficiency of crop production in Britain. Philosophical Transactions of the Royal Society, London, B 281: Natarajan M, R W Willey Sorghum-pigeonpea intercropping and the effects of plant population density. 2. Resource use. The Journal of Agricultural Science, 95:59-65 Shibles R M, C R Weber Interception of solar radiation and dry matter production by various soybean planting patterns. Crop Science, 6: Sivakumar M V K, S M Virmani Crop productivity in relation to interception of photosynthetically active radiation. Agricultural and Forest Meteorology, 31: Tsubo M, S Walker, E Mukhala. 21. Comparisons of radiation use efficiency of mono-/intercropping with different row orientations. Field Crops Research, 71: Willey R W Resource use in intercropping systems. Agricultural Water Management, 17: Zhang L, W van der Werf, et al. 28. Light interception and utilization in relay intercrops of wheat and cotton. Field Crops Research, 17: Zhu Y Y, Chen H R, et al. 2. Genetic diversity and disease control in rice. Nature, 46: Zhu Y Y, Li C Y, et al. 27. Genetic diversity for crops diseases sustainable management. Beijing: Science Press, (in Chinese) 玉米净作和间作植株间光强的时空分布 何汉明, 杨磊, 赵丽华, 吴晗, 范黎明, 谢勇, 朱有勇, 李成云 农业生物多样性与病虫害控制教育部重点实验室, 云南农业大学, 昆明 6521 摘要 : 作物多样性种植能够有效减少病虫危害, 显著增加产量, 但其中的机理尚不清楚 太阳辐射是最重要的影响因子之一 本试验研究了玉米净作 (A) 及玉米 / 大豆 2:2 (B,2 行玉米 2 行大豆 ) 和 2:4 (C,2 行玉米 4 行大豆 ) 两种间作模式下, 玉米冠层内太阳辐射强度的时空变化 研究结果表明, 多样性种植可在不同高度上对玉米植株间的受光强度和受光时间产生明显影响 在玉米穗期, 相比净作, 在 3cm 高度上,B 和 C 模式下光强都超过了 2 倍, 在 7cm 高度上, 光强超过 1 倍 花粒期, 在 和 21cm 位置上, 相比净作,B 和 C 模式下光强分别提高了 5 倍 2 倍和 12%, 而且随着测量高度的下降, 间作模式下光强下降较为缓慢 从第 7 18 叶, 相比净作, 各叶位间作模式下光强平均增加 2 倍, 而且日有效辐射时间平均提高了 5 小时 此外, 玉米的一些生物学性状, 如千粒重 每株产量和穗位叶叶面积等也表现出间作 B 和 C 模式都显著高于净作 因此, 间作提高了玉米的受光强度和有效辐射时间, 是改善玉米生物学性状的重要因子 关键词 : 间作 ; 玉米 ; 光强 ; 持续时间 ; 生物学性状