Soybean Intercropping Research Articles

Sunflower–Soybean Intercrop Productivity under Different Water Conditions and Sowing Managements

The sunflower (Helianthus annus L.)–soybean [Glycine max (L.) Merr.] intercrop has emerged as an option that increases land productivity in the southern Pampas of Argentina, compared with sole crops, because of complementary use of resources between species. A common management practice for this intercrop consists of delay soybean sowing, although delayed planting reduces the capacity of soybean to capture resources. Simultaneous sowing could improve total intercrop productivity because of an increase in soybean grain yield with no or little detrimental effects on sunflower grain yield. The objectives of this study were to analyze the response of the sunflower–soybean intercrop and of their component species under different sowing management (i.e., relay or simultaneous sowing) and water availability conditions. Three experiments were conducted at Balcarce, Argentina. Four cropping systems were evaluated: (i) sunflower–soybean intercrop with simultaneous sowing management (I00), (ii) sunflower–soybean intercrop with 30 d of delay between sunflower and soybean sowing (I30), (iii) sunflower sole crop (SUN), and (iv) soybean sole crop (SOY). Sunflower–soybean intercrop grain yield tend to be higher than that for sole crops of the component species. This yield advantage for intercrop increased with water availability and was associated with an increase in intercropped soybean productivity. Intercrop sowing management had no effect on total intercrop grain yield. However, simultaneous sowing increased soybean contribution to intercrop yield. Finally, our results indicate that agronomic practices that promote intercropped soybean performance increase intercrop productivity relative to the sole crops of their component species.

Capture and use of water and radiation in summer intercrops in the south-east Pampas of Argentina

Intercrops are an alternative to intensify and diversify the agricultural systems in the south-east Pampas of Argentina. The aim of this study was to evaluate resource capture and resource use efficiency in maize–soybean and sunflower–soybean intercrops and in their respective sole crops. Water and radiation capture, biomass and grain production were measured for sole crops and intercrops. Water and radiation productivities were estimated as the energy produced per unit of annual available resource. Comparisons of intercrops with soybean sole crops were emphasized because current soybean expansion in the region represents a threat to agricultural system sustainability.Intercrops showed an increase in crop duration when compared to their sole counterparts. Maize–soybean intercrop resulted in an improved radiation and water productivities compared with soybean sole crops. Maize cultivated as sole crop attained the highest resource productivity. On the other hand, resource productivity of sunflower–soybean intercrop was higher than or similar to its corresponding sole crops.The improvement in water productivity for intercrop compared with soybean sole crop was accounted for by an increase in water capture efficiency and, also, by an increase in water use efficiency in the case of maize–soybean intercrop.The increase in radiation productivity for maize–soybean intercrop compared with soybean sole crop was the result of an increase in radiation use efficiency and of a minor but significant increase in radiation capture efficiency. Contrarily, the improvement in radiation productivity of sunflower–soybean intercrop compared with sunflower or soybean sole crops was null or small.Grain yield of intercropped sunflower and maize was 20% lower than yield of sole crops. Therefore, yield attained by intercropping was mainly limited by a poor production of the soybean component. This work provides eco-physiological basis to improve management practices of summer intercrops.

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

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 30 cm above ground and 10-fold at 70 cm above ground, compared with monocropping. At the flowering to maturity stage, light intensity at 110. 160 and 210 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 7–18th 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.

Nitrogen fertilization and use efficiency in an intercrop system of cassava (Manihot esculenta Crantz) and soybean (Glycine max (L) Meril.)

Experiments were conducted at the Department of Crop Science, University of Nigeria, Nsukka Research farm during the 2008 and 2009 cropping seasons to determine the effects of intercropping cassava and soybean on cassava tuber and soybean grain yields respectively and on nitrogen use efficiency of cassava at the intercropping system. The experiment for each year was laid out in a factorial arrangement in randomized complete block design (RCBD). The treatments were the nitrogen rates, sole soybean (TGM 579), sole cassava (TMS 30572) and cassava + soy bean intercrop. Intercropping cassava with soybean showed a significant (P ≤ 0.05) yield advantage over sole cropping system in 2008. Increased fertilizer rates up to 90 kg N/ha -1 increased fresh cassava yield in sole cropping system, while in the intercrop, increased application of nitrogen at 60 kg N decreased cassava tuber yield. The cassava nitrogen use efficiency (NUE) increased with increase in applied nitrogen up to 60 kg N/ha -1 and then decreased beyond this point. Similar trend was observed in 2009, except that total harvested cassava tuber yield was significantly higher in 2009 than that obtained in 2008. This result suggests that intercropping cassava with soybean with or without application of nitrogen is beneficial but high doses of nitrogenous fertilizer in sole soybean field is uneconomical and should be avoided. Key words: Cassava, soybean, intercrop, sole crop, nitrogen use efficiency.

EFFECT OF FYM AND N FERTILIZER ON YIELD AND LAND USE EFFICIENCY OF MAIZE – SOYBEAN INTERCROPPING.

Two field experiments were carried out at Sanhout village Menia Al-Kamh district- Sharkia province under Agronomy Department supervision, Faculty of Agriculture, Zagazig University, Egypt, during two summer successive growing seasons i.e. 2009 and 2010.The investigation aimed to study the effect of farmyard manure (FYM) (Without, 20 and 40 m3 /fed.) and nitrogen fertilizer levels (Without, 45 ,90 and 135 kg N / fed.) on yield and land use efficiency of maize (Zea mays L.) – soybean (Glaycine max (L.) Merr.) intercropped. Soybean variety Giza-22 was sown at 93.333 plant per fed. as pure stand and intercropping as well and maize variety TWC 324 which was sown at 23,333 plant per fed. as pure stand and intercropping (3:3) were used in this investigation included: Pure stand of maize variety TWC 324 (23,333 plant per fed.), Pure stand of soybean variety Giza-22 (93.333 plant per fed.), maize was sowing on one side and two plants per hill (46.666 plant per fed) instead of one plant per hill in the solid plots, simultaneously, soybean was always sown and thinned as two plants in hill 10 cm apart on both sides of the ridge (186.666 plant / fed) instead of one side of the ridge in the solid plots (growing three ridges of maize in alternation with three ridges of soybean). The obtained results showed that: Grain and seed yields of maize and soybean components significantly reduced by intercropping ,compared to the pure stand yield, However, the relative yield of those two components was 82 and 85% for maize and soybean ,respectively. Thus, intercropping efficiency i.e. economic yield advantage of the combined intercrop yield reached 67% in the maize – soybean intercrop.Grain and seed yields of maize and soybean components were significantly increased due to FYM application up to 40 m3 and N up to 135 kg N / fed.Further more, land equivalent ratio (LER), area time equivalent ratio (ATER) and its LER average , land equivalent coefficient (LEC) and Agressivity (A) criterions were observed that addition of FYM did not have any significant effect on aforementioned traits in both seasons and their combined analysis. But, adding N fertilizer have significant effect on those traits (combined analysis). However, intercropping of maize and soybean, again, was more productive than growing them separately, as can be observed from the LER, ATER and its average values which were greater than unity and from the LEC values which were greater than 0.25 and from sign of agressivity values which were positive for soybean component and negative for maize at three FYM and four N fertilizer levels.

The challenge of placental bed disorders

A six-year (2010–2015) study of sugarcane (Saccharum officinarum) and soybean (Glycine max) intercropping combined with reduced nitrogen (N) fertilizer input was conducted to investigate sustainable agriculture via the functional soil microbial community in Southern China. The Illumina MiSeq platform and the microarray GeoChip 5.0 were applied in this study to detect the abundance, diversity and structure of bacterial and fungal communities, and to link specific functional genes with soil microbial-mediated N-cycling processes under experimental practice. The results revealed the α-diversity of bacterial communities to be relatively stable while the fungal α-diversity increased over the years. Intercropped sugarcane on rhizosphere soils under reduced and conventional N input harbor different bacterial and fungal community structures. Specifically, fungal α-diversity (e.g. Ascomycota and Basidiomycota) was found to be more sensitive to field practices while bacterial community (e.g. Bacteroidetes and Acidobacteria) changed moderately in abundance. Besides that, soil TN, AP, pH, and C/N ratio could explain the major variations in structure of soil microbial groups and in key functional genes. This study revealed the effect of N reduction and cropping patterns on functional traits based on both taxa and gene categories of microbial community, thereby improving understanding of structure-function relationships of microbial N-cycling processes in the different N input levels combined with cropping systems.

Soil aggregation and total diversity of bacteria and fungi in various tillage systems of sub-humid and semi-arid Kenya

Stable soil aggregates and high microbial diversity are essential for efficient nutrient recycling in soil. This study evaluated effects of different arable land-use systems on soil aggregation and associated composition and total diversity of bacteria and fungi. For this purpose, 5- and 3-year-old field trials were selected, two in sub-humid (orthic Acrisols and oxidic Ferralsols) and one in semi-arid (chromic Cambisol) region in Kenya. The treatments included combinations of tillage (conventional tillage [CT] and reduced tillage [RT]), crop residue management (0 and 2tha−1 maize stover) and cropping systems (continuous maize, maize–soybean intercropping and rotation) in the sub-humid sites, and of different tillage (CT, no-till and tied-ridging) and organic fertilization management (manure and crop residue) in semi-arid Kenya. The innovativeness of this study is the research in tropical soils where the concept of aggregate hierarchy is not generally accepted yet. The results showed that aggregate mean weight diameter (MWD) at 0–15cm depths had increased from 19 to 34% under RT relative to CT management (P<0.05). Crop residue additions also significantly increased MWD by 22% at the top 5cm (P<0.01) compared to treatments without residue in oxidic Ferralsols. At all the three sites, tillage resulted in greatest shifts of bacterial and fungal community composition, while cropping system had largest positive effect on the total microbial diversity indices. Total microbial diversity indices as well as MWD were higher in soybean–maize intercropping systems than under rotation or continuous maize cropping. Changes in total bacterial diversity related inversely to changes in the amount of free silt+clay, while fungal diversity related inversely to the contents of soil macro-aggregates >2mm (P<0.05). We conclude that RT plus supply of organic resources and intercropping are best strategies to increase total diversity of soil bacteria and fungi and improve soil structure in these tropical soils.

Efficacy of intercropping and harvest time modification for reducing field infestation of maize by Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

Most management practices of Sitophilus zeamais Motschulsky, a field-to-post-harvest insect pest of cereals, have focused on post harvest control methods. This experiment was designed to investigate the potential of cropping system and modification of time of harvest to control S. zeamais. Intercropping and harvest time modification had significant (P < 0.05) effect on the number of S. zeamais emerging 42 days post-harvest. For the early harvest (15 weeks after planting (WAP)), the mean number of S. zeamais recorded from a maize monoculture (7.39) was significantly (P < 0.05) higher than the mean numbers of weevils emerging from a maize–soybean intercrop (2.31), but not significantly higher than the number recorded in maize–groundnut (3.87) intercrop. For the late harvest (18 WAP), the mean number of emerged adult observed in the maize–soybean intercrop (6.13) was significantly lower than the mean number of adult emerging from the monocrop maize (13.24). Maize–groundnut intercrop did not significantly reduce field infestation of S. zeamais compared with monocrop maize. Percentage weight loss observed in early harvested maize was significantly (P < 0.0001) lower than what was observed in late-harvested maize. Percentage weight loss was highest in stored maize harvested from monocrop maize plots for the early harvest, whereas intercropping maize with soybean reduced percentage weight loss when harvest was delayed.

Effect of Intercropping and Crop Arrangement on Yield and Productivity of Late Season Maize/soybean Mixtures in the Humid Environment of South Southern Nigeria

Field experiments were carried out between September and December in 2007 and 2008 at Akamkpa (150 15'' N; 80 22'' E), Nigeria. The objective was to investigate yield and productivity of maize and soybean as sole crops and as additive mixtures (100:100) in response to five levels of nitrogen (0, 25, 50, 75 and 100 kg/ha) and five crop arrangements (sole maize at 53,333 plants/ha, sole soybean at 266,666 plants/ha and maize: soybean intercrop arrangements of 1:1, 2:2 and 1:2). The trial was a split-plot design in a randomized complete block with nitrogen in main plot and crop arrangement in sub-plot, with three replications. Intercropping had no significant effect on grain yield of maize in 2007. In 2008, maize grain yield grain yield reduction in mixture was 6 percent compared to sole cropping. Soybean seed yield reduction in mixture was 32 and 43 percents in 2007 and 2008, respectively. Crop arrangement significantly influenced yield components and yield in both maize and soybean. Planting maize and soybean in 1:1, 2:2 or 1:2 arrangement had no significant effect on maize in 2007 but depressed grain yield of maize by 38, 35 and 14 percents in 2008. Spatial arrangement of maize and soybean in 1:1, 2:2, and 1:2 depressed soybean yield by 51, 44 and 45 percents in 2007 and by 86, 64 and 73 percents in 2008. Intercropping reduced the relative maize grain yield by only 1 percent in 2007 and from 4 to 9 percents in 2008. Soybean relative yields were from 31 to 34 percent lower than sole crop yield in 2007 and 39 to 46 percent lower in 2008. The relative yield totals for both 2007 and 2008 were well above unity, an indication that the system was highly productive. This implies that intercrops were 64, 66 and 63 percents in 2007 and 43, 57 and 65 percents in 2008, more productive than the sole crops at 2:2, 1:2 and 1:1 arrangements, respectively. Late season maize and soybean may be planted in 2:2 or 1:2 arrangements to take advantage of optimum soybean seed yield and 65-100 percents of the maize grain yield in the humid South Southern Nigeria.

Effect of phosphorus fertilizer application on the performance of maize/soybean intercrop in the southern Guinea savanna of Nigeria

Field experiments were conducted at the Teaching and Research Farm, Ladoke Akintola University of Technology, Ogbomoso, Nigeria in 2007 and 2008 to determine the effects of phosphorus fertilizer application on performance of intercropped maize and soybean. The experiments, arranged as a split plot in a randomized complete block design, replicated four times. A cropping system with sole maize, sole soybean and maize/soybean intercrop formed the main plot treatments while P rates with 0, 15 and 30 kg P2O5 ha−1 were the subplot treatments. For both years, neither P fertilizer application nor cropping systems had a significant effect on maize grain yield. However, soybean grain yield was significantly higher (92.3% in 2007 and 44.5% in 2008) under sole cropping than under maize/soybean intercropping. On average, N fixed by soybean increased with the increase in P rate (from 51.8% without P to 60.5% with 30 P), but there was no significant difference in N fixed by sole soybean and soybean/maize intercrop. However, the interaction effect on N fixed between cropping systems and P rates was significant (P ≤ 0.05). N, P and K contents in maize grain were significantly higher (>100%) in intercropped maize than in sole maize. The cropping systems had no significant effect on post-harvest soil chemical characteristics. The land equivalent ratio was 1.52 in 2007 and 1.78 in 2008. The result shows that in utilizing legumes for N enrichment, the alleviation of P deficiency can enhance N2-fixation by legumes. Furthermore, P replenishment in a maize/soybean intercrop may improve maize grain quality even though yield is not increased.

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.

Effects of Shade on Nitrogen and Phosphorus Acquisition in Cereal-Legume Intercropping Systems

With increasing economic and environmental costs associated with fertilizer use, the need for low-input agroecological systems is on the rise. It is well documented that intercropping legumes can increase the supply of nutrients, through N2-fixation and P mobilization. Concurrently, the integration of trees in the agricultural landscape shows increasing evidence of nutrient inputs through efficient biogeochemical cycles. However, little is known about the effects shade has on legume-crop performance. This research aims to determine whether intercropping of the legumes soybean (Glycine max L. Merr.) and alfalfa (Medicago sativa) with wheat (Triticum turgidum durum) is beneficial for performance, particularly under shady conditions associated with tree-based intercropping. Test species were cultivated in hydroponics with a broad nutrient solution and steady state addition of N for 3 weeks. Individual plants were transferred to rhizoboxes with a 2 mm zone of soil for 16 days under (i) full sun or (ii) shade to mimic light levels at the tree-crop interface. Under monocropping, shading was found to significantly decrease wheat biomass. Intercropping wheat with alfalfa under full sun had no negative effect on growth but did increase wheat P uptake as compared to monocropped wheat. In contrast, intercropping wheat with soybean under full sun decreased wheat biomass, suggesting competition. However, under shade, this competitive effect was mitigated, as wheat exhibited similar biomass and higher N and P shoot concentration when associated with soybean as compared to monocropped wheat under lower light levels. This effect may be attributed to reduced biomass of soybean combined with higher soybean N2-fixation under shade. Legume-based intercrops may increase nutrient supply and growth but these beneficial effects will be dependent on matching species selection to light levels under tree-based intercropping.

THE IMPACT OF SOYBEAN AND CORN INTERCROPPING SYSTEM AND SOIL FERTILITY MANAGEMENT ON SOYBEAN APHID POPULATIONS APHIS GLYCINES (HEMIPTERA: APHIDIDAE) AND SOYBEAN GROWTH PERFORMANCE

Agricultural management cropping systems play an important role in affecting a crop plant’s ability to tolerate or resist insect pests. Field studies were conducted to examine the effect of two strategies management systems: fertilizer treatment and intercropping soybean with corn on soybean aphid (Aphis glycines Matsumura) population and soybean growth and yield parameters. The intercropping treatments were: soybean alone; 2:1 soybean/corn intercrop; and 3:1 soybean/corn intercrop. While the soil fertility treatments were the combination of NPK (urea 100 kg ha-1 + SP-36 200 kg ha-1 + KCl 200 kg ha-1) levels, dolomite (4 ton ha-1), compost (10 ton ha-1), and chicken manure (10 ton ha-1). The results of the first study showed that the intercropping soybean with corn significantly reduced the population density of soybean aphids. However, there were no significant effects of intercropping systems on soybean growth (plant height) and yield (number seed per pod and thousand seed weight) performances except on the number of soybean pods per plant. Meanwhile, the result of the second study indicated that soil fertilizer treatments had a significant effect on the soybean plant characteristics: leaf numbers; pod numbers; and plant height. Combining intercropping methods and soil fertilizer management offer an opportunity to protect the soybean plants by natural and sustainable pest management.

Polycultural manipulation for better regulation of planthopper populations in irrigated rice-based ecosystems

The frequent outbreaks of rice planthoppers, especially brown planthopper Nilaparvata lugens (Stål), in the last ten years in China and other Asian countries have caused serious rice (Oryza sativa L.) yield losses. The key problem is possibly due to biodiversity loss in rice ecosystems. We examined the potential of intercrops of soybean (Glycine max L.) and corn (Zea mays L.), both of which are more profitable than rice and mostly planted in levees, to diversify rice ecosystems and enhance insect pest management. We studied the impacts of such intercrops on planthopper populations and their natural enemies. The results showed significantly lower numbers of rice planthoppers in rice fields with intercrops of corn than in rice monocultures and rice fields with intercrops of soybean. Rice fields with corn intercrops had 26–48% fewer planthoppers than rice monoculture. Rice fields with soybean intercrops had lower rice planthopper abundance compared to rice monoculture in 2008 but higher in 2009. However, neither parasitoid nor predator numbers were significantly affected by intercropping. There were no significant differences in directional movements of planthoppers or natural enemies between crop subplots in the different cropping systems. Moreover, movement of planthoppers was very limited. Our study indicated that soybean and corn intercrops do not greatly enhance the ability of natural enemies to suppress planthoppers. However, rice fields with intercrops of corn had lower abundance of planthoppers and this strategy may be useful as part of an integrated pest management strategy for the sustainable rice production.

Soil Moisture and Soil Nutrient Content in Walnut-Crop Intercropping Systems in the Loess Plateau of China

Agroforestry has been widely applied in the Loess Plateau of China as a means of reducing soil and water losses, restoring ecological balance, and improving both land-use efficiency and economic returns. However, agroforestry also introduces a degree of competition for soil moisture and nutrients. Walnut (Juglans regia L.)–peanut (Arachis hypogaea L.) and walnut–soybean (Glycine max L. Merr.) intercropping systems that have been used throughout the Loess Plateau were selected as the basis for a study of agroforestry system—its advantages and its disadvantages with respect to soil moisture, soil nutrients, root distributions, yields, and economic returns. The results showed that soil moisture and nutrient levels were affected by intercropping with walnut trees, and that the degree to which they were affected decreased as distance from the trees increased. On the other hand, intercropping with walnut trees can increase land-use efficiency by 75% and economic returns by 17%. On the basis of the study findings, we conclude that walnut–peanut and walnut–soybean intercropping can be practical and beneficial in the study region, but irrigation and fertilization methods need to be further studied and improved, root barriers should be installed at the tree-crop interface, and the distance between crops and tree rows should be adjusted to minimize competition for soil moisture and nutrients.

Estimates of kinetic degradability parameters and passage of materials originated from intercropping of brachiaria grass and corn and soybean crops

The study was conducted to determine the kinetic parameters of in situ DM and NDF and the passage of particles of forages produced from the intercropping of brachiaria grass with corn and soybean crops. Three experiments were performed, as follows: Experiment 1 - Brachiaria grass intercropped with corn at different plant ages; Experiment 2 - Cultivation of brachiaria grass intercropped with corn set in different sowing arrangements; and Experiment 3 - Intercropping of brachiaria grass and soybean. Passage kinetic of particles was determined by the recovery of markers in feces. In order to obtain the ruminal degradation of DM and NDF, nylon bags were used at zero time, 3, 6, 9, 12, 24, 48, 72, 96, 120 and 144 hours. The particles' passage kinetic of corn with brachiaria grass silage and brachiaria grass silage presented 3%/h and 2.3%/h, respectively; and for soybean and brachiaria grass silage, it was 1.8%/h, which can be explained in part by the mixture of materials ensiled. The materials originated from the intercropping caused rumen fill. Degradation rates were lower when compared with literature data. The brachiaria grass silage obtained from corn and/or soybean crop-pasture integrated system is a feed with low nutritive value due to its low NDF degradation rate and low passage rate, causing rumen fill and, thus, possibly resulting in low intake and poor animal performance.

The response of late season maize/soybean intercropping to nitrogen in the humid environment of south Southern Nigeria

Field experiments were carried out between September and December in 2007 and 2008 at Akamkpa (15&deg; 15'' N; 8&deg; 22'' E), Nigeria. The objective was to investigate the productivity of maize and soybean as sole crops and as additive mixtures (100:100) in response to five levels of nitrogen (0, 25, 50, 75 and 100 kg/ha) and five crop arrangements (sole maize at 53,333 plants/ha, sole soybean at 266,666 plants/ha and maize: soybean intercrop arrangements of 1:1, 2:2 and 1:2). The trial was a split-plot design in a randomized complete block with nitrogen in main plot and crop arrangement in sub-plot, with three replications. Nitrogen fertilization increased yield in both maize and soybean at all the treatment levels, when grown sole or in mixtures. Application of 100kg N/ha to maize increased number of ears per plant, cob diameter, cob length, 100-grain weight, cob yield and grain yield by 46, 106, 95, 35, 138 and 153 percent, respectively in 2007, and by 15, 33, 63, 48, 88 and 109 percent, respectively in 2008, over no nitrogen application. Similarly, application of 100kg N/ha to soybean increased number of pods per plant, number of barren pods and 1000-seed weight by 53, 120 and 16 percent, respectively in 2007, and by 55, 99 and 14 percent, respectively in 2008, over no nitrogen application. Optimum seed yield in soybean was obtained at 50 kg N/ha. The yield values of 1,352.8 and 1,158.2 kg/ha were higher than those obtained at 0 kg N/ha by 31 and 21 percent in 2007 and 2008, respectively. Increasing the nitrogen level further to 100 kg/ha depressed seed yield by 8 percent in 2007 over 0 kg/ha. The nitrogen x crop arrangement interaction effects on grain yield and all other parameters were not significant (p&lt; 0.05). Late season maize and soybean may be planted at 50 kg N/ha to take advantage of optimum soybean seed yield and 66-76 percent of the maize grain yield.Keywords: maize, soybean, intercropping, additive mixtures, interplant arrangement

Investigation Corn and Soybean Intercropping Advantages in Competition with Redroot Pigweed and Jimsonweed

Investigation Corn and Soybean Intercropping Advantages in Competition with Redroot Pigweed and Jimsonweed

Harvest Aid Application Timing Affects Wheat and Relay Intercropped Soybean Yield

Early‐seeded soybean [Glycine max (L.) Merr.] relay intercropped into standing wheat (Triticum aestivum L.) using soybean seed‐coat technology may allow profitable wheat production in the Midwest on highly erodible soils. Dry conditions in mid‐ to late June have reduced relay intercropped soybean stands and yield in some years. We hypothesized that using glyphosate as a wheat harvest aid would reduce the impact of wheat interference on relay intercropped soybean grain yield and increase gross margins. Field research conducted over four site‐years in upstate Missouri evaluated timings for application of glyphosate as a harvest aid on wheat and relay intercropped soybean. The cost effectiveness of these cropping systems was compared to full‐season soybean, double‐cropped wheat–soybean, and wheat‐only production systems. Glyphosate applied to wheat 1 wk before harvest, after late dough, in a relay intercrop production system with coated‐soybean maintained wheat grain yields similar to nontreated wheat, and increased soybean grain yields 290 to 770 kg ha−1 compared to nontreated wheat relay intercropped or double‐cropped with soybean. Earlier glyphosate application timings (2–3 wk before wheat harvest) reduced wheat grain yields 10 to 25% and grain density 3 to 13%, but soybean yield increased 430 to 520 kg ha−1 compared to nontreated wheat in a relay intercrop system. A relay intercrop system with seed coat technology and glyphosate as a harvest aid may allow farmers to maintain wheat in their crop rotation while minimizing risk associated with early fall frost or dry conditions at seeding that may otherwise decrease double‐crop soybean yields.

Yield response to plant density of maize and sunflower intercropped with soybean

Maize–soybean and sunflower–soybean intercrops have the potential for increasing yield per unit land area and time in fully mechanized farming systems. The objectives of this work were to measure the land equivalent ratio index of maize and sunflower intercropped to soybean, to assess the effects of plant density of its components, and to gain insight into ecophysiological processes affecting their yield determination. Maize–soybean and sunflower–soybean intercrops and their respective sole crops were grown at Balcarce, Argentina during two growing seasons. Treatments included a wide range of plant densities for sole and intercropped sunflower (2–9 plants m −2) and maize (4–12 plants m −2). Plants were harvested to determine shoot dry matter and grain yield per plot and at the individual plant level. Land equivalent ratio index (LER) increased 11% (mean of the two years) when plant density of sunflower was reduced from 6 to 3 plants m −2; and LER increased 5% (year 1) or it was maintained (year 2) when maize plant density was reduced from 8 to 4 plants m −2. Yield response to plant density of sunflower and maize influenced LER. The response to plant density of intercropped sunflower and maize grain yield followed the same pattern than that in a sole crop, and grain yield of intercropped sunflower or maize were lower than those for the sole crops at each plant density except at the lowest sunflower plant density. Yield reductions from sole crop to intercrop at each plant density averaged 20% and were associated (i) with lower intra-row spacing in the intercrop and (ii) with a lower shoot production rather than to a change in the dry matter partitioning to reproductive structures; in addition, detrimental effects of soybean over maize or sunflower yield were undetectable.