Wheat/maize or wheat/soybean strip intercropping: II. Recovery or compensation of maize and soybean after wheat harvesting

While early-maturing crops benefit from intercropping, late-maturing crops usually suffer growth penalties during the intercropping phase. It is possible, however, that recovery or compensation of the late-maturing crops occurs after the harvest of the early-maturing crops. Three field experiments were conducted at Baiyun in 1997 and at Jingtan in 1997 and 1998 to test the hypothesis in wheat/maize and wheat/soybean intercropping. The biomass and nutrient accumulation in intercropped soybean were significantly smaller than in sole soybean before wheat harvest but thereafter increased sharply at Jingtan site in 1997. The rates of dry matter accumulation in the intercropped maize (10.0–20.1 g/m² per day) were significantly lower than those in the sole maize (17.1–34.8 g/m² per day) during the early stage from 7 May to 3 August, while mostly intercropped with wheat. After 3 August, however, the rates of intercropped maize, increasing to 58.9–69.9 g/m² per day, was significantly greater than in sole maize (22.7–51.8 g/m² per day) at Baiyun site in 1997 and nutrient acquisition showed the same trends as growth. At Jingtan site in 1998, the disadvantage of the border row of intercropped maize resulted from interspecific competition diminished after wheat harvest and disappeared at maize maturity. It was concluded that there was indeed recovery of growth after wheat harvesting in wheat/maize and wheat/soybean intercropping. However, the recovery was limited under N₀P₀ treatment. The interspecific competition, facilitation and recovery are together contributed to yield advantage of intercropping.     

Isoflavonoid Accumulation Pattern as Affected by Shading from Maize in Soybean (Glycine max (L.) Merr.) in Relay Strip Intercropping System

Abstract

Soybean is the most common resource of isoflavonoid in human food. Wide development of relay strip intercropped soybean has contributed to the soybean industry in China. Due to the shading from maize, growth and grain production of soybean is reduced. However, whether soybean isoflavonoid accumulation pattern is influenced in the relay strip intercropping system is still unclear. Here, we studied the accumulation patterns of soybean isoflavones in the relay strip intercropping system and sole cropping system at the per-harvest stage. The accumulation patterns of soybean isoflavones at the postharvest stage were also studied. The results indicated that accumulation patterns of soybean isoflavones of all varieties in leaf and seed in the two systems were similar, but the trend was delayed in the relay strip intercropping system compared with the sole cropping system. During the pod filling stage, the total content of isoflavone, M-type isoflavone content, G-type isoflavone content in seed in the relay strip intercropping system were lower than those in the sole cropping system. During the after-ripening period, seed isoflavone content, M-type isoflavone content, G-type isoflavone content in seed increased in both systems, but were higher in the relay strip intercropping system. The temperature and photosynthetically active radiation were significantly lower in relay intercropping than in sole cropping, while relative humidity showed the opposite trend. Path analysis showed that total isoflavone content in leaves and seeds showed a significantly positive correlation with temperature and photosynthetically active radiation, but significantly negative correlation with relative humidity. Correlation analysis between the highest isoflavone content in sole cropping or relay intercropping seeds and agronomic traits revealed a significant positive correlation between the number of both branches and pods with total isoflavone, M-type isoflavone and G-type isoflavone in both systems.     

Comparisons of radiation use efficiency of mono-/inter-cropping systems with different row orientations

Intercropping may be helpful to solve future food problem in developing countries. The aim of this study was to compare production efficiency in intercropping with sole cropping in terms of radiant energy use. For analysing crop radiation capture and utilisation, three indices are often used: the fraction of radiation intercepted (F), radiation use efficiency (RUE) and harvest index (HI). Using those indices, maize–bean intercropping was evaluated and compared with maize and bean sole cropping systems. The findings were as follows: the intercrop F was higher than the sole crop F, the sole maize RUE was higher than the others, and there was no difference in HI among cropping systems. From those results, the intercropping may be equivalent to maize sole cropping in the overall efficiency of radiation interception and use. Therefore, when it is considered that both maize and beans would be planted in a given area of land, intercropping has more efficient radiation harvests than sole cropping. No effect of row orientation was found on F, RUE and HI.     

Land Equivalent Ratio of Groundnut-Fingermillet Intercrops as Affected by Plant Combination Ratio,and Nitrogen and Water Availability

Abstract

Field experiments were conducted to characterize intercropping advantages in groundnut-fingermillet intercrop in relation to crop combination ratios, soil moisture and nitrogen (N) availability. Three intercrops in 1 : 2, 1 : 1 and 2 : 1 alternating rows of groundnut and fingermillet were examined for their growth and yield in comparison with their respective sole crops in 1996. The effect of well watered (W) and water stressed (D) conditions on the intercropping advantage was also examined for 1 : 1 intercrops in 1995 and 1996. Fertilizer N was applied at the rate of 20 kg ha^?1 in 1995 and 50 kg ha^?1 in 1996. The total above-ground biomass (DM) and its land equivalent ratio (LER) were highest in the 1 : 1 combination ratio. The DM production of intercropped fingermillet was higher in 1996 with higher N than in 1995 with low N application, while those of groundnut were similar in both years. The intercropped groundnut exhibited significantly higher DM production after the fingermillet harvest. The LERs in grain yield were higher in 1996 (1.43 under W and 1.45 under D), than in 1995 (0.87 under W and 1.22 under D). Also, LERs were consistently higher under D than W conditions. Water stress severely reduced the leaf area index (LAI) of fingermillet at a low N, especially in the later stages, whereas higher N alleviated the water stress effect. A close linear relationship was observed between LAI and leaf area (LA) per unit leaf N both for groundnut and fingermillet, with intercrops producing larger LA per unit leaf N than sole crops. Intercropping maintained higher ability in leaf net photosynthesis and transpiration of groundnut up to later stages, and significantly reduced water evaporation from the soil surface under the canopy than sole cropping of fingermillet. These results suggest that three processes associated with the intercropping yield advantages in the groundnut-fingermillet intercrop; 1) higher leaf photosynthesis and vigorous growth of groundnut after the fingermillet harvest, 2) higher LA production per unit N and 3) efficient water use. In conclusion, interspecific shading was considered to be the key mechanism associated with these processes, leading to the intercropping advantages. The degree of the interspecific shade and its effect on growth and yield depended on the available soil N and water.     

Maize plant types suitable for present and possible bean relay systems in Central America

This study explores the effect of maize plant type on yields of bush and semi-climbing beans (Phaseolus vulgaris) planted at maize physiological maturity and describes how rainfall and pests determine the variants of this relay system used by farmers in Central America. It also investigates the possibility of avoiding end-of-season drought in bean relay crops by advancing their planting date relative to maize. Two trials to maize cultivars × bean planting data × bean cultivars in relay cropping were planted under experimental station conditions in Costa Rica. Two complementary trials were planted on farmers' fields in Nicaragua. There were no interactions of maize cultivar × bean cultivar, indicating that within the relay system, genetic improvement of maize and bush or semi-climbing beans may proceed separately, rather than simultaneously. When beans were planted at maize physiological maturity, differences in bean yield in relay with different maize cultivars were not significant. The mean advantage over sole cropping was 18%. When, however, beans were planted 20 days before maize physiological maturity, less-leafy maize cultivars depressed bean yield by 7%, while more-leafy cultivars depressed bean yield by 32%. Although the less-leafy maize cultivars used were earlier and yielded less, there was an economic advantage in using these, provided that the bean: maize price ratio was above 2.45. In order to plant beans before maize physiological maturity, attention should be paid to breeding less-leafy maize cultivars which are not earlier maturing and thus yield the same as present cultivars, while competing less with beans.     

Water use and yield of wheat/maize intercropping under alternate irrigation in the oasis field of northwest China

A field experiment was carried out to investigate the effects of alternate irrigation (AI) on the yield, water use and water use efficiency (WUE) of wheat (Triticum aestivum L.)/maize (Zea mays L.) intercropping system in an oasis region of northwest China in 2006-2008. Three planting patterns, i.e., sole wheat, sole maize and wheat/maize intercropping. Three irrigation levels were applied for each treatment during 3 years. Results showed that land use efficiency of wheat and maize was significantly enhanced by intercropping system; land equivalent ratio (LER) of wheat/maize intercropping system in different treatments was all greater than 1.0. Moreover, significant difference in grain yield was observed between intercropping treatment and sole cropping treatment, in which the yield of intercropped wheat was 55.37-74.88% of sole wheat, and intercropped maize was 66.63-78.87% of sole maize. Wheat/maize intercropping treatments increased water use by 1.8-16.4% than half of the total water use of sole-cropping wheat and maize. Compared to sole cropping wheat treatments, wheat/maize intercropping with alternate irrigation significantly improved water use efficiency (WUE) by 30.5-57.7%, 55.5-71.4% and 12.0-19.8%, and increased by 32.7-37.8%, 9.5-15.8% and 4.0-20.8% than sole cropping maize treatments in 2006-2008, respectively. Our results suggest that AI should be a useful water-saving irrigation method on wheat/maize intercropping in arid oasis field where intercropping planting is decreased because of limited water resource.     

Potato intercropping systems with maize and faba bean

Potato is a major cash crop for Bhutanese highland farmers, who widely use intercropping systems combining potato (Solanum tuberosum) with maize (Zea mays). Scarcity of information on existing cropping practices limits the scope of present extension programs. Experiments evaluating potato intercropping systems with maize and faba bean (Vicia faba) were conducted at Yusipang (2700 m) and Kangma (1900 m). Potato yield reductions through intercropping ranged from 0–21 percent depending on year, and location. Variation in planting geometry and maize planting date did not affect potato yield reductions. The land equivalent ratio ranged from 1.03–1.06 for faba bean and from 1.11 to 1.49 for maize intercropping systems. Compared to potato as a sole crop maize intercropping increased gross benefits in Kangma by 12–15 percent with maize plant densities of 2.8 per m². In Yusipang, gross benefits were not increased through intercropping. Reducing risks of environmental and market impacts favor the use of intercropping systems.     

恩施山区马铃薯与玉米、蔬菜立体种植模式

为了增加单位面积产值,充分利用有限的耕地,恩施州农户巧妙地将马铃薯与玉米、蔬菜进行立体种植,获得相当可观的经济效益。本研究在充分调查的基础上对这种立体种植模式进行了试验。研究方法为在海拔855m的地方采用双行玉米套种单行马铃薯,在玉米生育期内套种两季四季豆、一季白萝卜;对照为传统双行玉米套种单行马铃薯。试验结果为:立体种植模式马铃薯商品薯667m2产量达615.9kg,玉米产量达614.6kg,四季豆产量达1577.0kg,白萝卜产量达2755.0kg,667m2总产值达4149.4元,净产值达3044.9元,比传统种植模式的净产值增加509.7%。     

4种间作作物对夏秋季茶园主要叶部病害发生的影响

为了寻求适合高山茶园的间作模式,探究不同间作作物对茶园主要叶部病害发生的影响。本文通过田间试验,明确川西北茶园主要叶部病害种类;通过对茶-黄豆、茶-玉米、茶-李树、茶-厚朴间作茶园和单作茶园的病害发生情况进行调查研究,比较分析不同模式茶园叶部病害发生的差异性。结果表明,川西北高山茶园主要叶部病害为茶饼病、茶炭疽病、茶云纹叶枯病、茶圆赤星病和茶赤叶斑病;4种间作作物中黄豆和玉米是较为理想的间作作物。茶-黄豆间作的茶园茶饼病和茶炭疽病发病率最低,两种病害发病率分别比单作茶园降低了85.12%和74.34%;茶-玉米间作茶园炭疽病发病率比单作茶园降低了49.76%。茶-厚朴间作茶园茶饼病的平均发病率为27.82%,是单作茶园的11.50倍。同时茶-厚朴间作茶园9月份炭疽病的发病率高达51.67%是单作茶园发病率的2.73倍。因此,黄豆和玉米是替代厚朴等林木类较为理想的高山茶园间作作物,间作黄豆可显著降低茶园病害的发生,减轻病害的损失。     

玉米行距对大豆/玉米间作作物生长及种间竞争力的影响

为探明大豆玉米间作系统中玉米种植行距对间作作物生长及种间资源竞争的影响。在固定带宽的大豆/玉米间作系统中,设置10,20,45,60和70 cm 5个间作玉米种植行距,分析间作系统的间作优势、作物生长情况以及大豆相对于玉米的资源竞争力变化。结果表明:随间作玉米行距增加,间作优势增加,70 cm行距间作优势最大,达4 271.4 kg·hm^-2。Logistic生长拟合曲线表明:随玉米行距增加,大豆生物累积量减小,达到最大日生长速率峰值的天数缩短,玉米生物累积量最大值出现在D45处理下,达43 471.1 kg·hm^-2,D45处理达到最大日生长速率峰值的天数最长,达130 d,且生长后期日生长速率持续高于其它处理;共生期内,伴随作物生长,大豆相对于玉米的资源竞争力A_sm逐渐降低,共生后期,表现为随间作玉米种植行距增加,大豆相对于玉米的竞争力A_sm逐渐减小。综合分析表明:河西灌区大豆/玉米间作系统中,玉米是强竞争力作物,玉米种植行距为45 cm,有利于大豆和玉米的生长及产量形成,大豆和玉米种间竞争力较弱,可作为河西灌区大豆/玉米间作系统中间作玉米的最佳行距配置。     

Silage fermentation profile,chemical composition and economic evaluation of millet and soya bean grown in monocultures and as intercrops

In recent years, dairy farmers in semi‐arid regions have shifted from maize (Zea mays L.) as their primary source of feed to drought‐tolerant crops, such as millet (Pennisetum glaucum L.), due to lack of water for irrigation. However, millet alone may not provide feed of sufficient quality and crude protein content for dairy cows. A field experiment was conducted in 2 years to evaluate (i) whether intercropping millet with a relatively drought‐tolerant soya bean cultivar (Glycine max Merr, cv. Williams) could improve silage quality with minimum yield penalty, and (ii) if the application of molasses could further enhance the nutritive value of silage of millet–soya bean intercrops. There were three intercropping ratios (60% millet with 40% soya bean, 50% millet with 50% soya bean, 40% millet with 60% soya bean) and monocultures of millet and soya bean. Mixed forages were treated with three levels of molasses: M₀ (without molasses), M₁, and M₂ (2·5 and 5% fresh matter respectively). Inclusion of soya bean in millet crops resulted in decreased silage yield compared with millet alone. The highest yield was obtained from the ratio of 60% millet with 40% soya bean. Molasses‐treated silage had higher lactic acid, lower pH, and lower acid detergent fibre (ADF) and neutral detergent fibre (NDF). Silage produced from millet–soya bean intercrops exhibited enhanced fermentation, indicated by lower pH (3·64) and higher lactic acid (16·63 g kg^?1 DM) than silage from monocultures. Intercropping ratios had lower water‐soluble carbohydrate, ADF and NDF than millet monoculture. Overall, an intercropping ratio of 60% millet with 40% soya bean was advantageous over other ratios in terms of higher yield, nutritive value and economic value.     

Intercropped wheat (Triticum aestivum L.) and bean (Vicia faba L.) as a whole-crop forage: effect of harvest time on forage yield and quality

Abstract Sole crops and intercrops of wheat (Triticum aestivum L.) and bean (Vicia faba L.), at three harvest dates, representing successive growth stages, were evaluated for biomass production of whole‐crop forage and quality characteristics of crude protein (CP), neutral‐detergent fibre (NDF), acid‐detergent fibre (ADF), water‐soluble carbohydrate (WSC) concentrations and ash content. These tests were carried out for two field experiments, respectively, drilled during the spring of 1997 and autumn of 1997 on Imperial College Farm, Wye, UK. Results indicated that optimum forage yield and quality were obtained from the second to third harvest dates for the spring‐drilled experiment and the second harvest for the autumn‐drilled experiment. Wheat and bean intercrops were higher in total forage dry matter (DM) yield than either wheat or bean grown as sole crops. Field bean intercropped with wheat led to increased forage quality (CP and NDF concentrations) compared with sole wheat, and higher WSC concentrations compared with sole bean. Intercrops also enhanced weed suppression compared with sole bean. It is suggested that winter wheat–bean intercrops may have considerable potential as a moderate‐yielding, relatively high‐quality, low‐input and environmentally benign forage crop with considerable potential with regard to yield and quality and warrant further study.     

Crotalaria (C. ochroleuca G. Don.) as a green manure in maize–bean cropping systems in Uganda

Crotalaria (C. ochroleuca G. Don.) used as a green manure may improve the productivity of maize–bean cropping systems in eastern Africa. To test this hypothesis, three field studies were conducted over three consecutive cropping seasons at Kawanda Agricultural Research Institute in Uganda. In the first season, crotalaria biomass was produced in pure stands or in intercrop systems with either common beans (Phaseolus vulgaris L.) or maize (Zea mays L.) as companion crops. Crotalaria was sown at planting and three weeks after planting the food crops. The biomass of early planted crotalaria was mulched, that of late planted crotalaria was incorporated into the soil at planting of the following crop. The first subsequent crop was maize, and the second was either beans (in two seasons) or maize (in one season). In the crotalaria production season, mean yield losses of maize through intercropping with early or late sown crotalaria were 40 and 22%, respectively; the corresponding values for beans were 45 and 14%. In the first cropping season after crotalaria production, the increase in maize grain yield on account of crotalaria averaged 39%; the best response (68% increase) to crotalaria was obtained with early sown sole crotalaria applied as mulch. Major differences in soil mineral nitrogen content among the treatments occurred at the six-leaf stage of maize only. In the second cropping season following crotalaria production, the mean increases in seed yields of beans or maize, due to crotalaria, were 23 and 19%, respectively, indicating a considerable residual effect of crotalaria green manure. The decrease in bulk density, and the increase in water infiltration capacity of the soil suggest that the yield stimulation because of crotalaria not only resulted from the increased nitrogen supply, but also from more favorable soil physical properties. Considering the competitive effect of crotalaria with the food crops and the positive effect on yields of subsequent crops, two options are especially promising: incorporation of crotalaria produced by relay intercropping with beans and mulching of early sown crotalaria produced in pure stands.     

Effect of cropping system on genetic variability and component analysis in soybean

The nature and magnitude of genetic variability and component analysis was assessed in 50 diverse genotypes of soybean grown in monoculture and in association with maize. Cropping system effects and interaction of cropping systems with genotypes were significant for all traits except 100-seed weight, oil % and protein %. Branches/plant, total pods/plant, pod clusters/plant, harvest index and seed yield/plant decreased under intercropping. There was no effect of cropping system in the manifestation of phenotypic and genotypic variability. The estimates of heritability and genetic advance for seed yield components were less in the associated cropping system than in the sole crop. Genotypes interacted differentially to the different cropping systems. The performance of as many as 30 genotypes was comparable under both cropping systems. Fourteen genotypes recorded reduction in seed yield/plant under intercropping. However, the performance of six genotypes was higher under intercropping. Among the commercial varieties, the performance of ‘Bragg’ and ‘Hardee’ was comparable under both cropping systems. ‘Punjab-1’ performed better in associated cropping, while ‘Shilajeet’ and ‘Lee’ performed better under sole-crop.The correlation coefficients between traits were found to differ, both in nature and magnitude, between monoculture and intercropping. In monoculture, seed size, harvest index and oil % were positively related with seed yield. By contrast, plant height, branches/plant, pods/plant and pod clusters/plant, besides 100-seed weight and harvest index, were correlated with seed yield under intercropping. Seed size followed by branches/plant appeared to be the important characters to undertake selection for higher seed yield under sole-crop. Yield improvements in intercrop were associated with increased harvest index. Genotypes and the characters to be utilized to develop varieties suitable for sole-crop and intercropping have been suggested.     

Intercropping in a temperate environment for irrigated fodder production

Fodder crops such as maize and oats are very productive under irrigation in a temperature environment; however, their protein content is too low for rapidly growing or lactating animals. Intercropping with legumes could help overcome this protein limitation.Dry matter (DM) production, protein content and total protein yield were measured in a range of intercropping combinations. For summer fodder production, maize (Zea mays L.) was intercropped with lablab bean (Lablab purpureus L.) or soybean [Glycine max (L.) Merr.]. For winter production, oat (Avena sativa) was intercropped with field pea (Pisum sativum).Alternative-row maize-plus-soybean was the most promising intercrop combination. Averaged over two years, the intercrop yield was 14.1 t¹/ha compared with a sole maize yield of 17.5 t/ha, while protein contents were 93 and 71 g/kg. In one of the two years protein production per unit area of the intercrop was significantly greater than that of sole maize.Intercropping with lablab bean planted in the same rows as maize increased protein content by approximately 10 g/kg. Reducing the maize population to one third of normal (2.4 vs 7.2 plants/m²) decreased maize yield and increased lablab bean production in one year but had no effect in the next year. Intercropping with soybeans in the same row as maize was less effective than with lablab bean.The oat-with-pea intercrops were similar to maize-with-lablab bean in raising the protein content about 10 g/kg. None of the planting patterns used reduced the dominance of the oats to a level where the peas contributed more than 10% of the total DM.     

玉米-大豆带状套作高产玉米品种的形态特征

通过两年大田试验,在玉米-大豆带状复合种植模式下,研究21个玉米品种在净作和套作模式下的产量水平,以产量为7 500 kg/hm~2为界限,将供试玉米品种划分为3个产量类别,通过比较净作高产套作高产与净作高产套作低产两个类别下玉米的形态特征,从品种间形态的变异系数和形态指标与产量相关性,筛选出叶面积、株高、穗上位二叶夹角和穗位高可作为选择套作高产玉米品种的主要形态指标。套作玉米品种叶面积吐丝期为6 415～7 158 cm~2/株,穗上位二叶夹角分别为20°～31°和22°～28°,株高为259～280 cm,穗位高为94.5～113.0 cm时,可获得较高的套作玉米产量。     

Faba bean in cropping systems

The grain legume (pulse) faba bean (Vicia faba L.) is grown world-wide as a protein source for food and feed. At the same time faba bean offers ecosystem services such as renewable inputs of nitrogen (N) into crops and soil via biological N₂ fixation, and a diversification of cropping systems. Even though the global average grain yield has almost doubled during the past 50 years the total area sown to faba beans has declined by 56% over the same period. The season-to-season fluctuations in grain yield of faba bean and the progressive replacement of traditional farming systems, which utilized legumes to provide N to maintain soil N fertility, with industrialized, largely cereal-based systems that are heavily reliant upon fossil fuels (=N fertilizers, heavy mechanization) are some of the explanations for this decline in importance. Past studies of faba bean in cropping systems have tended to focus on the effect of faba bean as a pre-crop in mainly cereal intensive rotations, whereas similar information on the effect of preceding crops on faba bean is lacking. Faba bean has the highest average reliance on N₂ fixation for growth of the major cool season grain legumes. As a consequence the N benefit for following crops is often high, and several studies have demonstrated substantial savings (up to 100–200 kg N ha⁻¹) in the amount of N fertilizer required to maximize the yield of crops grown after faba bean. There is, however, a requirement to evaluate the potential risks of losses of N from the plant–soil system associated with faba bean cropping via nitrate leaching or emissions of N₂O to the atmosphere as a consequence of the rapid mineralization of N from its N-rich residues. It is important to develop improved preventive measures, such as catch crops, intercropping, or no-till technologies, in order to provide farmers with strategies to minimize any possible undesirable effects on the environment that might result from their inclusion of faba bean in cropping system. This needs to be combined with research that can lead to a reduction in the current extent of yield variability, so that faba bean may prove to be a key component of future arable cropping systems where declining supplies and high prices of fossil energy are likely to constrain the affordability and use of fertilizers. This will help address the increasing demand by consumers and governments for agriculture to reduce its impact on the environment and climate through new, more sustainable approaches to food production. The aims of this paper are to review the role of faba bean in global plant production systems, the requirements for optimal faba bean production and to highlight the beneficial effects of faba bean in cropping systems.     

Agronomic performance of no-tillage relay intercropping with maize under smallholder conditions in Central Brazil

In the context of conservation agriculture on small scale farms of the Brazilian Cerrado, we hypothesized that planting a cover crop in relay with a commercial crop improves the efficiency of use of available natural resources, increasing biomass for use as fodder without reducing the grain yield of the main crop. The objective of this study was to measure the performance of two intercropped systems in terms of total above-ground biomass production and maize (Zea mays) grain yield: pigeon pea (Cajanus cajan) and Brachiaria (Brachiaria ruziziensis) sown as cover crops in established maize under a no-tillage management. The cover crops were sown at two different dates and a comparison was made with the three crops sown as a sole crop at the early sowing date. The experiment was conducted during the 2007-2008 and 2008-2009 growing seasons. Maize grain yield was not reduced by the presence of the relay cover crops in comparison with maize as the sole crop, even when the cover crop was sown soon after maize emergence. In contrast, the production of above-ground biomass by the cover crop was significantly lower when grown with maize than it was when grown as a sole crop. In the intercropped systems, when sown early, the cover crop produced higher total biomass than when sown late. Total above-ground biomass production of maize intercropped with a cover crop was much higher than that of any of the crops sown alone: the total biomass (average of the two growing seasons) produced by maize and pigeon pea was more than double that of maize grown alone. The land equivalent ratio (LER) of maize grain yield and biomass production was higher than one whatever the intercropped system used. It was particularly high when maize was intercropped with early sown pigeon pea; grain yield LER and biomass LER reaching, respectively, 1.72 and 1.73 in 2007-2008 and 2.02 and 2.03 in 2008-2009. These high LER values provide evidence for the complementary and the high efficiency of use of available resources by the intercropped plants and thus the advantage of such systems to produce both maize grain and cover crop forage under the conditions of our study.     

玉米花生带状间作对植株氮吸收和土壤微生物群落的影响

为探明玉米花生带状间作模式下植株氮吸收利用和土壤微生物群落特征,设置玉米单作（SM）、花生单作（SP）和玉米花生间作（IMP）三种种植模式,系统分析了不同种植模式下氮素吸收利用规律,并采用16S/ITS测序技术明确玉米花生带状间作系统下根际土壤细菌/真菌群落结构变化。结果表明,间作玉米边行优势明显,地下和地上部干物质积累量和氮积累量显著高于单作玉米和间作玉米中间行。间作玉米和间作交互区根际土壤细菌和真菌多样性和丰富度降低,而间作花生根际真菌多样性和丰富度增加,其中变形菌门、担子菌门、子囊菌门等有益菌最为显著富集。土壤中细菌和真菌存在复杂的相关性,变形菌门与子囊菌门正相关。间作丰富了物种功能多样性,参与氨基酸运输、代谢和碳水化合物代谢的细菌和腐生营养型真菌的显著富集,改善了植物养分吸收,促进了植株生长发育。可见,玉米花生间作可通过优化土壤微生物的群落结构,促进植株对氮素的吸收和利用,本研究为玉米花生带状间作氮营养互促吸收提供了科学依据。     

宁夏引黄灌区胡麻套种玉米带型优化研究

对宁夏引黄灌区胡麻套种玉米不同带型的作物产量、生育表现和经济效益进行了研究,结果表明：作物总产与玉米产量呈高度正相关（r＝0．99**）,玉米产量与其占地面积比例呈正相关（r＝0．99**）.据此认为在套种条件下,胡麻与玉米的面积比例应以0．60：0．40～0．65：0．35为宜;带宽为2．25m,胡麻1．35m,玉米0．9m的处理B和带宽为2．05m,胡麻1．35m,玉米0．7m的处理A为较佳带型。