Strip Intercropping System Research Articles

Application and Theory of the Corn-soybean Strip Intercropping System in Southwest China

Application and Theory of the Corn-soybean Strip Intercropping System in Southwest China

A Study on Sorghum (Sorghum bicolor L.) + Chickpea (Cicer arietinum) Intercropping Systems with Varying Row Proportions on a Semiarid Vertisol

A field experiment was carried out during rabi 2008 to 2012 at Mulegaon farm of All India Coordinated Research Project for Dryland Agriculture, Solapur Maharashtra to find out suitable geometry for sorghum + chickpea strip intercropping system on Vertisols under dryland condition. Among the various row proportions studied, sorghum + chickpea (3:3) at 45 cm row spacing system was found to be promising and registered significantly higher net returns ( 28676/ha), sustainable yield index (0.41), better land equivalent ratio (1.43) and rainwater use efficiency (31.93 kg/ha-mm) over the respective sole crops followed by sorghum + chickpea (2:6) at 30 cm row spacing ( 28537, 0.67, 1.43 and 32.81 kg/ha-mm, respectively) and sorghum + chickpea (2:1) at 30 cm row spacing ( 27593, 0.60, 1.33 and 30.96 kg/ha-mm, respectively).

Responses of soybean lodging and lodging-related traits to potassium under shading by maize in relay strip intercropping system

The relay strip intercropping system of maize-soybean is dominant in southwest China. Compared to monoculture, the productivity of soybean is unstable in this system, since soybean seedling grow under shading by maize, which beget elongated plants and prone to lodging. Therefore, a 3-year study was conducted to determine the influence of K on lodging and lodging-related traits of soybean, and to identify the key traits associated with lodging resistance in relay strip intercropping system in Sichuan Province, China during 2008-2010. The results showed that K application significantly affected basal stem diameter, stem breaking strength, total nonstructural carbohydrate (TNC) concentration, concentration of K and lignin, while differences in plant height and weight of basal internode were not significantly. The K-fertilized treatments had higher seed yield and seed ratio than treatment without K application. The lodging had significantly negative correlation with grain yield, seed ratio, basal stem diameter, weight of basal internode, stem breaking strength, concentration of lignin and K, but no correlation was observed between lodging and TNC in both pot and field trial. The plant height was positively correlated with lodging only in field trial. Thus, these results suggested that K application could alter the lodging-related traits in soybean for greater lodging resistance, and it may be worthwhile to focus on basal stem diameter, stem breaking strength, and lignin concentration.

Responses of Root Growth and Nitrogen Transfer Metabolism to Uniconazole, a Growth Retardant, during the Seedling Stage of Soybean under Relay Strip Intercropping System

Relay strip intercropping of soybean has been widely developed in the southwest of China to secure China's soybean production. However, due to the shading from maize, soybean plants are thin and have a poor root system. Uniconazole is a plant-growth retardant that could enhance root vigor; increase root length, root volume, and root dry weight; and affect nitrogen (N) metabolism. To understand the effects of uniconazole on the root growth and N-transfer metabolism of soybean seedlings under relay strip intercropping, the changes in some morphological characteristics of root, dry-matter weight, root vigor, nitrate (NO3 −)-N, ammonium (NH4 +)-N, and amino acid of xylem sap after seed treatment with uniconazole powder (0, 2, 4, and 8 mg kg−1 seed) were investigated. Main root length, total lateral root lengths, first lateral root numbers, root nodule numbers, root vigor together with bleeding sap, bleeding sap–top ratio, root dry weight, and root/shoot ratio were increased, indicating uniconazole improved soybean root system in relay strip intercropping. Uniconazole powder treatment could increase NO3 −-N, NH4 +-N, and total amino acid of xylem sap, to increase the potential of leaf and root N reduction and assimilation, and increase of leaf and root N contents. Thus, results suggested that uniconazole treatment can improve root growth and N transfer mechanism of soybean to support its further growth.

Modeling light availability for a subordinate crop within a strip–intercropping system

The shift of rural laborers out of the agricultural sector led to a steady decrease of intercropping in the North China Plain (NCP). Strip intercropping facilitates mechanized management, and has the potential to out yield monocropping by an optimized resource use of the intercropped species. Therefore we developed a light partitioning model, that calculates the available amount of photosynthetically active radiation (PAR) at the top of the canopy for a given point within a strip of a smaller, subordinate crop. The model was described, evaluated on various simulation time steps and tested for the purpose of designing strip–intercropping systems. PAR reaching the top of the canopy of various rows of the strip subordinate bush bean (Phaseolus vulgaris L. var. nana) was measured continuously under different sky conditions. In the dominant strip, maize (Zea mays L.) was grown. Then the model was tested for its ability to account for the influence of different widths of the bush bean strip, strip orientations and maize canopy architecture (height, leaf area index, and leaf angle distributions). Comparison between hourly averaged simulated and observed values of PAR across the bush bean strip showed a high accuracy of the simulations, under both, clear and cloudy conditions. Overall, simulations of hourly values of PAR across the bean strip showed a root mean square error (RMSE) ranging between 47 and 87μmolm−2s−1 and a percent bias (PBIAS) ranging between −3.4 and 10.0%. A simulation time step of 20min is recommended to preserve the accuracy of the model across the strip. The model captured reasonably the influence of strip design (width and orientation) and maize canopy architecture. Results suggested that the highest potential to increase PAR across the bush bean strip is by reducing height and leaf area index of maize, especially in the most shaded border row adjacent to the maize strip. The model proved to be a helpful tool for understanding the characteristics of light availability across the strip of the subordinate species and can be further used to examine a number of strip intercropping arrangements prior to labor and time consuming field trials.

Growth of soybean seedlings in relay strip intercropping systems in relation to light quantity and red:far-red ratio

Maize–soybean intercropping is a common system in several countries. However, different spatial patterns of maize and soybean can directly affect the light environment of soybean growth under this system through the combined effects of the altered light quality and the reduced light quanta. This work aimed to investigate the differences in the light environment of the soybean canopy in terms of the red:far-red (R/FR) ratio and the photosynthetically active radiation (PAR) as well as the different rates of soybean seedling growth under maize–soybean relay strip intercropping and soybean sole planting, to analyze the relationship between the morphological characteristics and the light environment, and to assess the relative contributions of the R/FR ratio and PAR transmittance to soybean seedling growth in intercropping conditions.Field experiments were performed in 2011–2013. The intercropping patterns involved the wide-narrow row planting of alternating maize and soybean. The light environment of the soybean canopy and the morphology of the soybean seedlings were estimated in the relay strip intercropping system by changing the distances of the maize and soybean rows as well as the number of maize vs. soybean rows per strip. These parameters of the intercropping system were compared with those of the soybean monocultures. Furthermore, the relationship between the light environment of the soybean canopy and its morphological parameters were analyzed using correlation analysis.Incident light in maize–soybean relay strip intercropping systems was partly reflected and absorbed by maize leaves. Thus, the spectral irradiance, R/FR ratio, and PAR of the soybean canopy were decreased with maize–soybean intercropping as compared to soybean monocropping. Simultaneously, the stem diameter, root length, aboveground biomass, total root biomass, and root–shoot ratio of relay intercropped soybean were reduced significantly, while its seedling height was increased. The correlation relationship between morphological parameters of soybean and the light environment (R/FR ratio and PAR transmittance) in different planting pattern were significant (P<0.05). Compared to PAR transmittance, the R/FR ratio of the relay intercropped soybean canopy was strongly correlated with morphological parameters of soybean seedling (P<0.01), and the correlation coefficients were higher than 0.88. The response of soybean seedlings to shading by maize was not solely influenced by the PAR or the R/FR ratio. It may be the summed effects of both parameters under relay strip intercropping systems. Therefore, the results reveal the physiological response mechanisms of soybean seedlings to changes in the quality and amount of light, which may support the building three-dimensional growth model of the responses of plant to light quantity and quality, and guide the identification of suitable population planting patterns in the intercropping system in the future.

Modeling evapotranspiration in maize/soybean strip intercropping system with the evaporation and radiation interception by neighboring species model

An experiment was carried out at Shangqiu Agro-Ecosystem experimental station in 2008–2009 to determine the partitioning of evapotranspiration in a maize/soybean intercropping. Sap flow gauges and micro-lysimeters, were used to determine plant transpiration and soil evaporation. Average daily soil evaporation in the intercropping system during the observation period (from June 1 to June 30) in 2008 and 2009 seasons were 2.07 and 2.41mmd−1, respectively. During the observation period, the mean transpiration rates of maize and soybeans in the intercropping arrangement were 1.47 and 0.78mmd−1, respectively. A multi-source model – the ERIN (evaporation and radiation interception by neighboring species), was used to simulate soil evaporation and plant transpiration in the maize/soybean intercropping. Results showed that the ERIN model overestimated plant transpiration of maize and soybean, while the mean bias error (MBE), the root mean square error (RMSE) and the index of agreement (d) were 0.06mmd−1, 0.23mmd−1 and 0.93, respectively. However, the ERIN model underestimated soil evaporation; MBE, RMSE and d were −0.02mmd−1, 0.44mmd−1 and 0.97, respectively. Sources of error were attributed to the uncertainties in characterizing the micrometeorological conditions and specifying the empirical parameters of the resistance terms. The multi-source model was extremely sensitive to the water vapor deficit at canopy source height and the radiation captured by crop and stomatal resistance. Overall, the ERIN model is useful in simulating the partitioning of evapotranspiration in intercropping systems.

Assessment of yield and yield components of corn (Zea mays L.) under two and three strip intercropping systems

Intercropping can be described as the growing of two or more crops simultaneously on the same field. In order to investigate the effects of three spices (corn, soybean and sunflower) strip intercropping on yield and yield components of corn (Zea mays L.) a field experiment was carried out as randomized complete block design (RCB) with three replications in 2011. Results showed that the chlorophyll content of corn significantly affected by neighboring of soybean and sunflower. The maximum chlorophyll content of corn leaves was obtained at intercropping of corn-soybean, additive corn-soybean, corn-soybean-sunflower and corn-soybean-sunflowersoybean while, minimum chlorophyll content of this cultivar was showed at pure culture of corn. The effect of different intercropping on number of leaves, height of plant and diagonal of ear and biological yield of corn was not significant. The most ear length, number of rows in ear, number of grain in row, grain weight, grain yield and harvest index of corn were showed at intercropping of corn-soybean and corn-soybean-sunflower-soybean. The neighboring of sunflower by beside of corn significantly inhibited yield and yield component of this cultivar as the lowest yield of corn was obtained at intercropping of corn-sunflower.

Productivity of strip intercropping systems in agro-pastoral ecotone

Strip intercropping system is not only a technique that achieves high productivity but also an important practice to protect winter and spring wind erosion in Agro-pastoral ecotone. Dry matter accumulation process and yield advantage of intercropping are vital indicators for exploration of intercropping performance and assessing the environmental benefit. This study is aiming to quantify crop growth, yield and land productivity in typical intercropping systems in agro-pastoral ecotone. An expolinear relationship between biomass growth and heat sum of above 0°C temperature was fitted for different crops in the inter-and mono-cropping systems. The regression parameters were used to quantify the delay of crop growth in the intercropping. Land equivalent ratio (LER) was used to explain land productivity and over-yielding of the intercropping systems. The main results showed that sunflower/potato, oats/potato and oats/bean strip intercropping systems with wider width of strips (e.g. 2 m:2 m intercropping) significantly increased land productivity with yield land equivalent ratio (LER) of 1.12, 1.09 and 1.05, respectively, which means 5% to 12% of the land productivity increasing. Intercropping yield advantages were significantly higher in the wider strip intercropping systems than that with narrower ones (1 m:1 m intercropping), and had a less yearly variation. The harvest index (HI) of sunflower was significantly increased in intercropping, while that for other crops were significantly changed. A border row effect was clearly found in the oat based intercropping systems. The border rowers had a significantly higher yield compare to middle rows in the intercrops and sole oats. Strip intercropping decreased the maximum growth rate cm, while the relative growth rate rm stayed as the same as the monoculture. The growth delay of crops in the intercrops was quantified by using the parameter tb, which indicated the thermal time requirement at the time of reaching maximum canopy cover. The growth of five species in the intercropping systems, e.g. sunflower, potato, oats, faba bean and vetch, were delayed 117 to 387 degree days compared to that of monocultures, which resulted 8-26 d of growth delay when we took the daily average temperature (15°C) into accounts. All in all, Strip intercropping systems not only have over-yielding effects and higher economic benefits, especially in intercropping systems with wider strips, but also reduce the agricultural risks in the agro-pastoral ecotone climatically and economically.

Effect of Wheat/Maize/Soybean and Wheat/Maize/Sweet Potato Relay Strip Intercropping on Bacterial Community Diversity of Rhizosphere Soil and Ni-trogen Uptake of Crops

为探讨小麦/玉米/大豆和小麦/玉米/甘薯套作体系中根际细菌群落多样性与作物氮素高效吸收的差异特性及二者间的关系，应用变性梯度凝胶电泳(DGGE)技术研究了小麦–大豆(A1)、小麦–甘薯(A2)、玉米(A3)、小麦/玉米/大豆(A4)和小麦/玉米/甘薯(A5)5种种植模式的根际细菌群落多样性。结果表明，与A1、A2、A3及A5相比，A4套作提高了各作物在开花期(或吐丝期)与成熟期的籽粒吸氮量、地上部总吸氮量和Shannon-Weiner index多样性指数( H ′)。处理间的吸氮量与 H ′的变化规律为套作>单作、大豆茬口>甘薯茬口，以A4处理最高。不同种植模式下DGGE图谱条带的数量及亮度有较大区别，且有几条特征性条带发生了明显变化。不同种植模式间的细菌群落结构相似性较低，群落相似度系数( Cs )表现为套作与套作间>套作与单作间；A4与A5间的 Cs 相对较小，二者间的细菌群落结构差异较大。A4模式有利于提高根际细菌群落多样性，增强植株对氮素的吸收能力。

Dependence of the productivity of maize and soybean intercropping systems on hybrid type and plant arrangement pattern

Intercropping systems could improve utilization of the most important resources (soil, water and nutrients), provide a better control of weeds, pests and diseases, and finally higher productivity, especially under rain-fed growing conditions. This study aimed to determine the effects of three maize (Zea mays L.) prolific hybrids (FAO 500, 600 and 700) and the spatial intercrop patterns on the above-ground biomass and grain yields of maize and soybean (Glycine max L. Merrill), on chernozem soil type at Zemun Polje, Belgrade, in 2003, 2004 and 2005. The experimental design was a complete randomized block with four replications and three treatments: 3 rows of maize and 3 rows of soybean in strips for each maize hybrid (three variants, 3 rows of maize and 3 rows of soybean in alternate rows for each hybrid (another three variants) and monocrops of both maize and soybeans. To optimize the ecological and economic benefits of maize/soybean intercrop in terms of yield, variety selection and compatibility of the component crops should be made using established agronomic management practices involving the two crops. Suitable maize varieties for maize/soybean intercrop systems are varieties that have less dense canopy. These varieties would therefore have lesser shading effect to the understory beans. However, establishment of an appropriate spatial arrangement of the component crops would be essential to alleviate negative effects especially on the less competitive crop. The intercropping system in alternate rows showed significantly higher above-ground biomass and grain yields in comparation with both the strip intercropping system and maize monocrops in 2004. Soybean gave significantly lower above-ground biomass and grain yield in intercrops than in monocrops. Maize prolific hybrid growing in intercropping with soybean as legume crop, increased productivity of cropping system, especially in favourable agroecological conditions. Maize and soybean yields reduction could have also been due to interspecific competition for resources such as nutrients and water. Moreover, performance of the currently grown varieties in the semi-arid regions depends on the amount of rainfall received during the growing season.

How to Overcome the Slow Death of Intercropping in the North China Plain

Intercropping has a strong potential to counteract the severe degradation of arable land in the North China Plain (NCP). However, a rapid decline of intercropping can be observed in the last decades. The present paper investigates the reason for this development and suggests solutions on how to adjust intercropping systems to fit modern agriculture. Firstly, the developments of socioeconomic conditions for farming were assessed, analyzing the statistical yearbooks of the seven provinces of the North China Plain. Secondly, a survey was conducted in the study region to understand the current state and future of intercropping systems. The investigations revealed that, due to limited off-farm income possibilities in the past, intercropping has been a viable solution to intensively use the limited land resources per farm household. However, a shift of rural laborers into other sectors has recently been observed. Thus, decreasing importance of income from agriculture and increasing labor costs are heralding the slow death of labor-intensive intercropping systems. Two possible solutions are discussed in the paper. Either the traditional row-intercropping systems can be transformed into strip-intercropping systems that can be mechanized using existing machinery; or, new machinery has to be developed that enables the mechanization of the traditional row-intercropping systems.

Effect of phosphorus and potassium nutrition on growth and yield of soybean in relay strip intercropping system

A field experiment was conducted to determine the effect of Phosphorus (P) application (0, 8.5, 17.0 and 25.5 kg ha-1) and Potassium (K) application (0, 37.5, 75.0 and 112.5 kg ha-1) on growth and yield of soybean (Glycine max (L.) Merr.) in relay strip intercropping system. The plant height, stem diameter, branch number and leaf area increased at first and then decreased with the increment of P application, but the performance of lodging rate showed oppositely. By applying K from 0 to 112.5 kg K ha-1, plant height, lodging rate, unfilled pod ratio, and 100 seeds weight were significantly reduced, while pods per plant, seeds per pod, and harvest index remarkably increased. The Highest benefit in growth and seed yield was obtained at rates of 17.0 and 112.5 kg ha-1 for P and K, respectively. Application of 17.0 kg P ha-1 at the rate of 112.5 kg K ha-1 gave 18.5, 13.7, and 4.0% higher seed yield than its application at rates of 0, 37.5, and 75 kg K ha-1, respectively. In conclusion, the findings suggested that the combination of P (17.0 kg ha-1) and K (112.5 kg ha-1) can maximize productivity of soybean in the relay strip intercropping system. Keywords: Phosphorus, potassium, growth, yield, relay strip intercropping soybean.

Corn and Soybeans in a Strip Intercropping System: Crop Growth Rates, Radiation Interception, and Grain Yield Components

Crop growth rates (CGR), radiation interception (IPAR), yields, and their components were determined in two crops monocultures (using one corn and two soybean genotypes) and in intercropped “strips,” during three growing seasons. Corn yield in the strips significantly increased in the three seasons (13–16%) as compared to that in the monocultures. This response was due to increased yield in corn plants of the border rows of the strips, which was highly correlated to an increased IPAR, allowing high CGR at critical crop stages. As a result, more dry matter was partitioned to grain and also an increased number of ears per plant were generated. Conversely, yields of soybeans in the strips were 2 to 11% lower than that in the monocultures, with variable significance depending on soybean cultivar and/or year. Grain number per unit area was the yield component most closely associated to yield variation in both crops. We believe that if yield components of this system are more closely identified, more appropriate genotypes will fit into strip intercropping, thus contributing to the spread of this technique and thus to the sustainability of actual massive monocultured agricultural systems.

Non-hydraulic root-sourced signaling and grain yield stability under shade of maize during progressive soil drying in soybean

Production practice shows shaded soybean in wheat-maize-soybean; relay strip intercropping system has better tolerance to drought as compared with sole cropping soybean. Our researches are to understand the reasons through non-hydraulic root signals (nHRS), yield and the relationships among them. Pot experiments were conducted with two soybean cultivars, under shade of maize (LI) and normal irradiance (HI). nHRS were traced during manipulative progressive soil drying period at branching stage under good soil conditions (HW), water stress treatment (LW), in 2010. Well-watered (WW), light drought (LD), moderate drought (MD) and severe drought (SD) were applied in 2009. In response to soil drying, nHRS appeared earlier in Gongxuan No.1 (GX) than Gongqiudou 05-8 (GQ) under two irradiance treatments, but it disappeared earlier for GX than GQ under normal irradiance. GX exhibited a wider average soil water content threshold range (TR) of nHRS under low irradiance. Drought stress significantly decreased the shoot dry mass, root mass and grain yield (P<0.05), excluding LD and nHRS treatments. Water use efficiency was significantly higher (P<0.05) in GX than GQ under drought conditions in both irradiances. In a conclusion, soybean cultivar GX has wider TR in low irradiance condition, light drought had no significant effect on yield, nHRS maybe beneficial to maintain soybean yield under drought condition. Key words: Soybean, drought, shade, non-hydraulic root-sourced signal, water use efficiency, yield stability.

Combination of lettuce and rocket cultivars in two cultures intercropped with carrots

The intercropping practice is a viable technological option for the production of vegetables and the success of the association between crops will be greater the greater the complementarity between them. The present work was conducted from June to November 2006, at Universidade Federal Rural do Semi-Árido, Rio Grande do Norte State, Brazil, to evaluate the productive performance of two lettuce and two rocket cultivars in two cultures in strip-intercropping systems. The experimental design was randomized complete blocks, with five replications and treatments arranged in a 2 x 2 + 2 factorial. The treatments consisted of the combination of two lettuce cultivars (Babá de Verão and Tainá) and two of rocket (Cultivada and Folha Larga) intercropped with carrot 'Brasília' plus two additional treatments (two lettuce cultivars or two rocket cultivars grown in sole crop). In each block a plot with carrot in sole crop was grown. The evaluated traits in lettuce were plant height and diameter, number of leaves per plant, productivity and shoot dry matter mass. In rocket were evaluated plant height, number of leaves per plant, green mass yield and shoot dry matter mass; and in carrot: plant height, total and marketable productivity, besides root classes, in long and medium roots, short roots and scrap roots. The Tainá lettuce cultivar had the best yield performance both in sole crop and intercropping system. The Cultivada and Folha Larga rocket cultivars had similar yield performance in both cropping systems. Both lettuce and rocket crops had better productive performance in the second culture. The mean production of carrot marketable roots in intercropping systems was 68.3%, being 48.6% for long and medium roots and 19.7% for short roots, while in the sole crop the mean production of marketable carrot roots was of 75.0%, being 51.7% for long and medium roots and 23.3% for short roots.

Sweet potato (Ipomoea batatas L.)-based strip intercropping: I. Interspecific interactions and yield advantage

A field experiment was conducted at the Regional Centre of the Central Tuber Crops Research Institute, Dumduma, Bhubaneswar for three consecutive years (2006–2008) under rainfed conditions on Alfisols to quantify the effects of strip intercropping on crop yields and yield components. A significantly higher yield was obtained from sweet potato (Ipomoea batatas L.) border rows when pigeonpea (Cajanus cajan (L.) Millsp.) was intercropped. Analyses of sweet potato yield components indicated that the number of roots/plant, root length and root diameter were significantly higher in border rows when rice (Oryza sativa L.), finger millet (Eleusine coracana L.) and pigeonpea were used as intercrop compared to monoculture sweet potato. The number of tubers/plant of sweet potato in border rows was significantly lower when maize (Zea mays L.) was intercropped, but the root length and root diameter were found to increase compared to sole sweet potato. The yields of rice, finger millet, maize and pigeonpea in inside rows in strip cropping were a little higher than in monoculture. The yield difference was mainly due to an increase in the number of seeds/panicle or cob. Sweet potato was the dominant crop when grown with rice or finger millet, but it was the subordinate crop when grown along with maize or pigeonpea. Sweet potato yields were consistently higher in strip intercropping than in monoculture when calculated across all the strips on an equal area basis. A strip intercropping system involving sweet potato + pigeonpea resulted in a higher land equivalent ratio (1.31) and net return ( $623.9) compared to the other forms of intercropping and to monocropping.

Distribution of roots and root length density in a maize/soybean strip intercropping system

Abstract In a field experiment in the Yellow River Basin conducted in 2007 and 2008, it was found that, under full irrigation, the roots of maize not only penetrated deeper than those of soybean but also extended into soybean stands underneath the space between inner rows of soybean. The roots of soybean, however, were confined mainly to the zone near the plants. Horizontal growth of the roots of both the crops was confined mainly to the soil layer 16–22 cm below the surface, a layer that lay above an existing plough pan. Root length density (RLD) was much higher in the top layer (0–30 cm deep) and in the zone closer to the plants. The exponential model proved suitable to describe the RLD vertically and horizontally in both sole cropping and in intercropping.

The Ecological Effects of Young Elm Trees Belt-Pumpkin Strip Intercropping System at the Agro-Pastoral Ecotone in Northern China

Young elm trees belt-pumpkin strip intercropping was studied to solve the actual problem of resource losses in the large barren area resulted from reconverting cultivated land into forest in the agro-pastoral ecotone in northern China. The final objective was to realize effective utilization of the barren land with both ecological improvement and economic development. Field experiments were conducted together with laboratory analysis. The results indicated that the soil moisture level was remarkably increased in young elm trees belt-pumpkin strip intercropping because the pumpkin vines covered the gap between pumpkin planting-furrow and elm trees belt. The water use efficiency of the intercropping system was increased by 23.7-163.3% as compared with the single cropping. Elm trees belt-pumpkin strip intercropping changed the sequential succession trend of the grasses growing in the gap of the pumpkin planting-furrow. The annual grasses become the dominant vegetation. The nutritive value as fodder and yield of the annual grasses were also increased remarkably. The biomass of pumpkin, elm trees and grasses under intercropping increased by 24.4, 28.4 and 144.4%, respectively, as compared with those under single cropping. The land use efficiency was increased by 132%. It was also indicated that the soil erosion from the intercropping land was not increased due to pumpkin plantation. The differences in the soil erosion among intercropped area, elm trees belt and pumpkin strip with single cropping were not remarkable. Therefore, it was concluded that young elm trees belt-pumpkin strip intercropping is an effective way to utilize the barren land between the young elm trees belt and realize synergistic enhancement of ecological benefit and economic profit.

Seed Treatment with Uniconazole Powder Improves Soybean Seedling Growth under Shading by Corn in Relay Strip Intercropping System

The relay strip intercropping system of wheat-corn-soybean is widely used in southwest China. However, it is hard to obtain a stable production of soybean with this system, since soybean plants grow under shading by corn; the stems are thinner and susceptible to lodging. We examined the effects of seed treatment with uniconazole powder (0, 2, 4 and 8 mg kg-1 seed) on the growth of soybean seedlings under relay strip intercropping, some morphological characteristics and yield. The seedling height, first internode length, cotyledonary node height and leaf area per plant were decreased, while the stem diameter, root dry weight, shoot dry weight, root volume, leaf greenness and root to shoot dry weight ratio were increased by uniconazole treatment. The root vigor and root active absorption area were also increased significantly by uniconazole treatment. Moreover, 2 and 4 mg kg-1 uniconazole powder treatment increased shoot dry weight, number of pods per plant, number of seeds per pod and seed yield significantly. Thus, the results suggested that seed treatment with uniconazole powder at a suitable concentration can improve soybean seedling growth, resist the lodging and also increase the seed yield under shading by corn in relay strip intercropping system.