Relay Strip Intercropping Research Articles

Dynamic of recovery growth of intercropped soybean after maize harvest in maize–soybean relay strip intercropping system

AbstractRecovery growth is common in relay intercropping systems and is a useful practice to increase total productivity of these systems. A field experiment was conducted during 2014–2016 to investigate the phenotypic and physiological traits related to light interception and utilization changes and cultivars difference of soybean during the recovery growth period. Two cropping patterns (maize–soybean relay strip intercropping (RSI), analogous soybean monoculture (CK)) and two soybean cultivars (shade‐tolerant Nandou12 and shade non‐tolerant Jiuyuehuang) were evaluated. During the co‐growth period, the growth of both two soybean cultivars was suppressed and showed a series of shade avoidance traits. After maize harvest, the LAI and leaflet number of intercropped soybean exhibited rapid growth, the LAI of Nandou12 (3.09) and Jiuyuehuang (1.32) recovered to 79% and 43% of corresponding CK level, respectively. Subsequently, final biomass of Nandou12 (3972.7 kg ha−1) and Jiuyuehuang (2263.3 kg ha−1) recovered 85.7% and 52% of corresponding CK level, respectively. Leaf blade thickness of Nandou12 recovered to the corresponding CK level, while Jiuyuehuang was not. Pn recovered to 84.5% and 82.8% of sole Pn at 80 days after soybean sowing in 2015 and to 72% and 91.2% at 66 days after soybean sowing in 2016 for Nandou12 and Jiuyuehuang, respectively. The above recovery process promoted the recovery of pod formation and grain yield. The yield of Nandou12 (1159.5 kg ha−1) has no significant difference between the CK level (1325.5 kg ha−1) but significantly higher than that of Jiuyuehuang (566.8 kg ha−1). Taken together, some recovery growth did occur in Jiuyuehuang, but it did not completely compensate for the growth reduction that occurred during the co‐growth period. Shade‐tolerant soybean cultivar has more stronger recovery growth ability in LAI, leaflet number, leaf thickness, and photosynthesis after maize harvest, which promoted the recovery growth of aboveground biomass and grain yield.

Influence of pre-crops on growth and phosphorus uptake of maize and wheat in relay strip intercropping

Relay strip intercropping systems have the advantage of increasing land yield, but there are few studies on how pre-crops affect the grain yield and phosphorus (P) use of subsequent crops in such systems. Field experiments were carried out for four consecutive years, covering two complete cycles of the crop sequence, to evaluate the effects of pre-crops on crop yield, P uptake, and topsoil P balance of maize and wheat. Three pre-crops were used, i.e. fallow, pea, and rutabaga planted with two P levels with (+P) and without (0P) P fertilizer applied to maize and/or the wheat season. Pea significantly improved grain yield in cycle 1 and grain yield, biomass and P uptake of subsequently grown maize in cycle 2, compared with fallow, and P fertilizer application had no effect on maize yield, P uptake and above-ground biomass in cycle 1, but significantly improved yield and P uptake in cycle 2. Regarding the subsequently grown wheat, on average, pea significantly increased the wheat average yield by 11.57 % and 4.27 % under the 0P and + P treatment, respectively; and rutabaga had 5.22 % and 6.40 % higher wheat average yield than under the same conditions of fallow. Pea prominently improved the above-ground biomass, P uptake; soil Olsen-P in the 0–20-cm soil profile, and the inorganic Pi fraction concentration after two consecutive cycles, with a significant positive correlation between Olsen-P and most Pi fractions. Rutabaga prominently improved above-ground biomass and P uptake. The above parameters performed better under pea than rutabaga. P fertilizer application during the maize season barely affected the growth or P uptake of subsequently grown wheat, P applied during the wheat season, however, significantly enhanced agronomic traits and P uptake, and this effect was more pronounced under pea. We therefore conclude that pea as pre-crop is instrumental for subsequent maize and wheat production, and provides more benefits for farmers.

Effect of Ti treatments on growth, photosynthesis, phosphorus uptake and yield of soybean (Glycine max L.) in maize-soybean relay strip intercropping

Shade is the main growth and yield limiting factor for soybean seedlings in maize-soybean relay strip intercropping. Therefore, a field experiment was conducted to investigate the effect of titanium (Ti) foliar application on soybean under a maize-soybean relay strip intercropping system. In this study, the soybean plants were sprayed with Ti treatments (T0S = 0, T1S = 125, T2S = 250, T3S = 500 and T4S = 1000 mg L−1) under maize-soybean relay strip intercropping. The results have indicated that under intercropping environment, Ti application significantly affected the growth of the plants. The soybean plants supplied with Ti treatment (T1S) significantly improved soybean diameter and stem strength at both V5 and R5 stages. Ti application resulted in a significant increase in SPAD values in T1S (i.e. 31.69 % and 21.21 %) and T2S (i.e. 21.55 % and 22.19 %) in comparison to control at both V5 and R5 stage, respectively. Furthermore, foliar application of Ti (T1S) significantly increased photosynthetic rate by 33.15 % and 22.80 % at both V5 and R5 stages. The stomatal conductance (Gs) increased significantly in T1S (44.39 %) and T2S (31.30 %) at the V5 stage and in T1S (29.85 %) at the R5 stage, respectively in comparison to control leading to increase root and shoot biomass in both V5 and R5 stages except for treatment T4S. Analysis of stem anatomical structure, stem strength (lodging resistance), and phosphorus content revealed that foliar application of Ti not only improved the shade tolerance but also increased yield (16–17 %) of soybean under maize-soybean relay strip intercropping. Conclusively, foliar application of Ti could be helpful in mitigating the shade stress and increasing soybean yield under the strip intercropping system.

Improved post-silking light interception increases yield and P-use efficiency of maize in maize/soybean relay strip intercropping

Abstract Belowground and aboveground interactions are important in increasing yield and nutrient-use efficiency in intercropping. However, how the yield and P-use efficiency respond to shoot-root interactions in intercropping remains unknown. Maize in mono- and intercropping was grown under field conditions (regosol soil, initial Olsen-P 12.6 mg kg−1) with P supply of 0 and 35 kg P ha yr-1 (P0 and P35, respectively) for 3 years. Compared with monocropping, intercropping significantly increased grain yield (by 13.9 %) and plant P-use efficiency (45.1 %), which might be attributed to increasing light interception during the post-silking period. Both sufficient P supply (P35 treatment) and increased light interception delayed leaf senescence through minimizing the degradation of chlorophyll and remobilisation of P as well as increasing the expression of ZmSee2β gene that influences leaf longevity. Increased light interception associated with enhanced leaf longevity increased the duration of photosynthesis, which provided assimilates not only for achieving yield potential, but also for maintaining root growth. It is suggested that sucrose translocated to roots serves as a substrate for root growth and improves P uptake to satisfy the nutrient demand of expanding shoots. This work contributed to understanding of the resource-use efficiency in intercropping as regulated by shoot-root interactions.

Plant Growth Regulators Increase Soybean Yields by Delaying Leaf Senescence in Maize (Zea mays L.)-Soybean [Glycine max (L.) Merr] Relay Strip Intercropping System

Background: The shading caused by maize inhibited the growth of soybean, reduced the yield of soybean under maize-soybean relay strip intercropping system. To investigate whether foliar spraying different types of plant growth regulators could improve the growth and yield of intercropped soybean.Methods: A field experiment was conducted in 2018 to evaluate the effect of foliar spraying 6BA (6-benzylaminopurine), S3307 (uniconazole) and DTA-6 (diethyl aminoethyl hexanoate), at the soybean beginning flowering stage, on the growth and yield of three soybean varieties (i.e., Nandou 25 (ND25), Gongqiu 8 (GQ8) and Guixia 3 (GX3)).Result: The leaf area index of three soybean varieties were highest in DTA-6 at 35 days after spraying (DAS) and no significant difference (p less than 0.05) were observed among three plant growth regulators. The chlorophyll a and chlorophyll b content under 6BA and DTA-6 treatments were significantly higher than CK and S3307 at 35 DAS. The activities of antioxidant enzymes (i.e., SOD (Superoxide dismutase) and CAT (Catalase) and antioxidant substances (i.e., GSH (Glutathione) were increased after spraying 6BA, S3307 and DTA-6 in three soybean varieties at 35 DAS. Independent soybean varieties, foliar spraying 6BA, S3307 and DTA-6 increased the soybean yield, pods per plant, 100-grains weight and grain per plant and the effect of DTA-6 (60 mg l -1) treatment were best than others.

Effect of exogenous plant growth regulators on carbon-nitrogen metabolism and flower-pod abscission of relay strip intercropping soybean

Effect of exogenous plant growth regulators on carbon-nitrogen metabolism and flower-pod abscission of relay strip intercropping soybean

Yielding parameters, nutritional value of soybean seed and weed infestation in relay-strip intercropping system with buckwheat

ABSTRACT The aim of the study was to verify the hypothesis that intercropping of soybean with buckwheat will positively affect yielding parameters and nutritional value of soybean seed. The experimental scheme assumed intercropping of two soybean cultivars alternately with one and two rows of buckwheat. The control (C) was soybean in monoculture. Both Annushka and Mavka cultivars significantly increased seed yield in the intercropping system with one row of buckwheat as compared to control. The addition of two rows of buckwheat resulted in a significant decrease in seed yield of both soybean cultivars compared to control. The seeds of both cultivars had significantly higher fat content and better fatty acid composition in both variants of intercropping with buckwheat compared to soybean monoculture. Significant changes in the amino acid composition were noted in the seeds of Mavka cultivar, in which glutamic and aspartic acids were the most abundant and the cultivation with two rows of buckwheat additionally increased their content. Intercropping of soybean with buckwheat significantly reduced weed infestation in both tested soybean cultivars. The presented results confirm the assumed hypothesis and the most advantageous variant turned out to be the cultivation of soybean with one row of buckwheat.

Uniconazole, 6-Benzyladenine, and Diethyl Aminoethyl Hexanoate Increase the Yield of Soybean by Improving the Photosynthetic Efficiency and Increasing Grain Filling in Maize–Soybean Relay Strip Intercropping System

The shading caused by maize inhibited the growth of soybean, reduced the yield of soybean under maize–soybean relay strip intercropping system. To investigate whether foliar spraying different types of plant growth regulators could improve the growth and yield of intercropped soybean. We conducted a sequential field experiment in 2018 and 2019, with foliar spraying of uniconazole (S3307), 6-benzyladenine (6-BA), diethyl aminoethyl hexanoate (DA-6) and water (CK) on soybean at the anthesis stage. Results showed the value of leaf area index, and chlorophyll (a + b) content, and net photosynthesis rat of soybean leaves were highest under DA-6 and significantly higher than CK at 56 day after spraying (DAS). Foliar spraying 6-BA, S3307 and DA-6 increased the activities of superoxide dismutase (SOD), peroxide (POD), and catalase (CAT) of soybean leaves at 35 and 56 DAS. The soybean aboveground dry matter weight and the dry matter accumulation after flowering stage was highest under DA-6 treatment, and the dry matter transportation ratio and the proportion of dry matter in pods were highest under S3307 treatment. The value of maximum grain filling rate (Vmax) and mean grain filling rate (Vmean) of soybean were highest in S3307, while the value of active grain filling period (D) was highest in DA-6. The hundred-grains weight was highest in S3307, then followed by DA-6 and S3307. The pods per plant in DA-6 were significantly higher than in 6-BA and S3307 and increased by 25.4% and 32.9% compared to CK in 2018 and 2019, respectively. Foliar spraying DA-6 (60 mg L−1) has a better effect on increasing the physiological function and photosynthetic capacity of leaves, leading to improving the grain filling process and increasing the yield of relay-intercropped soybean.

Variable Light Condition Improves Root Distribution Shallowness and P Uptake of Soybean in Maize/Soybean Relay Strip Intercropping System

In this study, soybean root distribution in an inter-cropping system was influenced by various environmental and biotic cues. However, it is still unknown how root development and distribution in inter-cropping responds to aboveground light conditions. Herein, soybeans were inter- and monocropped with P (phosphorus) treatments of 0 and 20 kg P ha yr−1 (P0 and P20, respectively) in field experiment over 4 years. In 2019, a pot experiment was conducted as the supplement to the field experiment. Shade from sowing to V5 (Five trifoliolates unroll) and light (SL) was used to imitate the light condition of soybeans in a relay trip inter-cropping system, while light then shade from V5 to maturity (LS) was used to imitate the light condition of soybeans when monocropped. Compared to monocropping, P uptake and root distribution in the upper 0–15 cm soil layer increased when inter-cropped. Inter-cropped soybeans suffered serious shade by maize during a common-growth period, which resulted in the inhibition of primary root growth and a modified auxin synthesis center and response. During the solo-existing period, plant photosynthetic capacity and sucrose accumulation increased under ameliorated light in SL (shade-light). Increased light during the reproductive stage significantly decreased leaf P concentration in SL under both P-sufficient and P-deficient conditions. Transcripts of a P starvation response gene (GmPHR25) in leaves and genes (GmEXPB2) involved in root growth were upregulated by ameliorated light during the reproductive stage. Furthermore, during the reproductive stage, more light interception increased the auxin concentration and expression of GmYUCCA14 (encoding the auxin synthesis) and GmTIR1C (auxin receptor) in roots. Across the field and pot experiments, increased lateral root growth and shallower root distribution were associated with inhibited primary root growth during the seedling stage and ameliorated light conditions in the reproductive stage. Consequently, this improved topsoil foraging and P uptake of inter-cropped soybeans. It is suggested that the various light conditions (shade-light) mediating leaf P status and sucrose transport can regulate auxin synthesis and respond to root formation and distribution.

Recovery growth and water use of intercropped maize following wheat harvest in wheat/maize relay strip intercropping

Recovery growth is common in relay intercropping systems and is a feasible practice for increasing total productivity of these systems. Previous studies have focused on the description of recovery growth, but the physiological changes and water use assessment during the recovery growth period remain unclear. A field experiment was conducted in Yangling, Shaanxi province, China during the 2014–2015 and 2015–2016 growing seasons to investigate maize physiological characteristics, root morphology, and transpiration efficiency during the recovery growth period. Three cropping systems (sole wheat, sole maize, wheat/maize intercropping) and two water treatments (supplementary irrigation and rainfed) were evaluated. Wheat was more competitive than maize during the intercropping co-growth period. During the co-growth period, the aboveground dry matter of intercropped wheat was 20.1 %–37.8 % greater than for sole wheat and water consumption was 14.9 %–15.9 % greater than for sole wheat. However, plant height and aboveground dry matter of intercropped maize during the co-growth period were less than for sole maize. Total root length of intercropped maize under supplementary irrigation initially exhibited rapid growth after wheat harvest, especially in the border rows. Subsequently, aboveground dry matter showed recovery growth, with final aboveground dry matter (2-yr average) of border rows and inner rows being 1 % and 4.5 %, respectively, greater than sole maize dry matter. Relative chlorophyll content and photosynthetic rate of intercropped maize were 4.3 %–19.2 % and 1.7 %–15.9 %, respectively, higher than observed for sole maize under irrigated conditions. Transpiration efficiency of intercropped maize during the recovery period was 10 % and 50.9 % greater than observed for sole maize under irrigated conditions in 2015 and 2016, respectively. Some recovery growth did occur under rainfed conditions, but it did not completely compensate for the growth reduction that occurred during the co-growth period. Supplementary irrigation promoted recovery growth of intercropped maize. Recovery growth improves intercropped maize grain yield and efficient use of water resources.

Diversity of the Seedborne Fungi and Pathogenicity of Fusarium Species Associated with Intercropped Soybean.

Maize/soybean relay strip intercropping has been widely practiced in Southwest China due to its high productivity and effective application of agricultural resources; however, several seedborne diseases such as seedling blight, pod and seed decay are frequently observed causing severe yield loss and low seed quality. So far, the population and pathogenicity of the seedborne fungi associated with intercropped soybean remain unexplored. In this study, seeds of 12 soybean cultivars screened for intercropping were collected from three growing regions in Sichuan Province of Southwest China, and the seedborne fungi were isolated from the surface-sterilized seeds. Based on sequence analysis of ribosomal DNA internal transcribed spacer (rDNA ITS), 148 isolates were identified into 13 fungal genera, among which Fusarium covered 55.0% as the biggest population followed by Colletotrichum. Furthermore, Fusarium isolates were classified into five distinct species comprising F. fujikuroi, F. proliferatum, F. verticillioides, F. asiaticum and F. incarnatum through sequence analysis of translation elongation factor 1 alpha (EF-1α) and DNA-directed RNA ploymerase II second largest subunit (RPB2). Among them, F. fujikuroi accounted for 51.22% (42/82) and was isolated from 91.7% (11/12) soybean varieties. Pathogenicity assay showed that five Fusarium species were able to infect the seeds of soybean cultivar “Nandou12” and caused water-soaked or rot symptoms, while F. fujikuroi and F. asiaticum had much higher aggressiveness than other species with significant reductions of seed fresh weight and germination percentage. Accordingly, this study indicates that Fusarium species are the dominant seedborne fungi in the intercropped soybean in Sichuan, China, and this provides some useful references for the effective management of seedborne fungal diseases as well as soybean resistance breeding in maize/soybean relay strip intercropping.

Uptake and utilization of nitrogen, phosphorus and potassium as related to yield advantage in maize-soybean intercropping under different row configurations

Intercropping advantage occurs only when each species has adequate time and space to maximize cooperation and minimize competition between them. A field experiment was conducted for two consecutive years between 2013 and 2014 to investigate the effects of maize and soybean relay strip intercropping systems on the uptake and utilization of nitrogen, phosphorus, and potassium. The treatments included “40:160” (T1, maize narrow and wide row spacing of 40 and 160 cm, where two rows of soybean with a 40 cm row were planted in the wide rows. The area occupation ratio of maize and soybean both were 50% of the every experimental block), “80:120” (T2, maize narrow and wide row spacing of 80 and 120 cm, the soybean planting was the same as T1 treatment. The area occupation ratio of maize and soybean were 60% and 40% of the every experimental block), “100:100” (T3, one row of maize and one row of soybean with a 100-cm row. The area occupation ratio of maize and soybean was the same as T1 treatment), sole cropping of maize (CK1, The area occupation ratio of maize was 100% of the every experimental block), and sole cropping of soybean (CK2, The area occupation ratio of soybean was 100% of the every experimental block). The results show that, compared with the sole cropping system (sole maize), the economic yields in T1, T2, and T3 treatments increased by 761, 536, and 458 kg·ha−1, respectively, and the biological yields increased by 2410, 2127, and 1588 kg·ha−1. The uptake and utilization of nitrogen, phosphorus, and potassium in T1, T2, and T3 treatments were significantly higher than those in sole crops, and the nutrient advantage is mainly due to nutrient uptake rather than nutrient use efficiency. The land equivalent ratio values in T1, T2, and T3 treatments were 1.43, 1.32, and 1.20, respectively. In particular, the economic and biological yield in T1 treatment exhibited potential as an intercropping pattern.

Effect of 6-Benzylaminopurine on Morphogenesis and Production Process of Sweet Pepper (Capsicum annuum L.)

Effect of 6-Benzylaminopurine on Morphogenesis and Production Process of Sweet Pepper (Capsicum annuum L.)

Maize/Soybean Relay Strip Intercropping Reduces the Occurrence of Fusarium Root Rot and Changes the Diversity of the Pathogenic Fusarium Species.

Fusarium species are the most detrimental pathogens of soybean root rot worldwide, causing large loss in soybean production. Maize/soybean relay strip intercropping has significant advantages on the increase of crop yields and efficient use of agricultural resources, but its effects on the occurrence and pathogen population of soybean root rot are rarely known. In this study, root rot was investigated in the fields of the continuous maize/soybean strip relay intercropping and soybean monoculture. Fusarium species were isolated from diseased soybean roots and identified based on sequence analysis of translation elongation factor 1α (EF-1α) and RNA polymerase II second largest subunit (RPB2), and the diversity and pathogenicity of these species were also analyzed. Our results showed that intercropping significantly decreased soybean root rot over monoculture. A more diverse Fusarium population including Fusarium solani species complex (FSSC), F. incarnatum-equiseti species complex (FIESC), F. oxysporum, F. fujikuroi, F. proliferatum and F. verticillioides, F. graminearum and F. asiaticum was identified from intercropping while FSSC, FIESC, F. oxysporum, F. commune, F. asiaticum and F. meridionale were found from monoculture. All Fusarium species caused soybean root infection but exhibited distinct aggressiveness. The most aggressive F. oxysporum was more frequently isolated in monoculture than intercropping. FSSC and FIESC were the dominant species complex and differed in their aggressiveness. Additionally, F. fujikuroi, F. proliferatum and F. verticillioides were specifically identified from intercropping with weak or middle aggressiveness. Except for F. graminearum, F. meridionale and F. asiaticum were firstly reported to cause soybean root rot in China. This study indicates maize/soybean relay strip intercropping can reduce soybean root rot, change the diversity and aggressiveness of Fusarium species, which provides an important reference for effective management of this disease.

Dynamic process-based modelling of crop growth and competitive water extraction in relay strip intercropping: Model development and application to wheat-maize intercropping

Strip intercropping increases land use efficiency but the effect on water use efficiency is less well-known. Here we develop a modelling method to simulate the growth of an intercrop taking into account the acquisition of light and water by the component species in order to calculate the efficacy of light and water acquisition in an intercropping system as compared to sole crops. The model is parameterized, calibrated and validated using data on wheat-maize intercropping in Gansu province, Northwest China. Observed above-ground biomass was 1630 g m−2 for sole wheat and 1334 g m−2 for intercropped wheat while it was 3023 g m−2 for sole maize and 2259 g m−2 for intercropped maize. The average water use was 405 mm in sole wheat, 595 mm in sole maize and 711 mm in wheat-maize intercropping. Based on observed yields, the land equivalent ratio (LER) was 1.59 and the water equivalent ratio (WER) was 1.14, where LER and WER express the relative amounts of land and water needed to achieve the yields obtained in a unit area of intercrop using sole crops. These results indicate that relay strip intercropping of wheat and maize achieves an increase of land use efficiency of 59% and of water use efficiency of 14%. Overall the intercrop model gave satisfactory predictions, with coefficients of efficiency (CE) in validation of 0.86–0.97, 0.90–0.95, 0.85–0.91 and 0.98 for biomass of sole wheat, sole maize, intercropped wheat, and intercropped maize, respectively. Overall CE of water use was 0.95. Simulated LER and WER were similar to observed LER and WER. The results show that intercropping could be used to obtain more yield on less land with less water. Policies that limit water use per unit land and prohibit the use of intercropping on the basis of its high water use per unit area may therefore be counter-productive. The model for intercrop growth and development under water limitation may be used for exploring production possibilities under land and water constraints.

Yield gain, complementarity and competitive dominance in intercropping in China: A meta-analysis of drivers of yield gain using additive partitioning

Abstract Intercropping is known to increase the efficiency of land use, but no meta-analysis has so far been made on the yield gain of intercropping compared to sole cropping in terms of absolute yield per unit area. Yield gain could potentially be related to a relaxation of competition, due to complementarity or facilitation, and/or to the competitive dominance of the higher yielding species. The contributions of competitive relaxation and dominance were here estimated using the concepts of complementarity effect (CE) and selection effect (SE), respectively. We compiled a dataset on intercropping of grain-producing crops from China, a hotspot of strip intercropping in the world. We quantified the yield gain and its components and analysed the contribution to yield gain of species traits (C3, C4, legume, non-legume), complementarity in time and nutrient input. Total yield in intercrops exceeded the expected yield, estimated on the basis of sole crop yields, by 2.14 ± 0.16 Mg ha−1 (mean ± standard error). Ninety percent of this yield gain was due to a positive CE while the remaining 10 % was due to SE. The net yield gain increased with temporal niche differentiation (TND) which is the proportion of the total growing period of the crop mixture during which species grow alone. The mechanism underlying yield gain shifted from competitive dominance of the higher yielding species when there was more overlap in growth period between the two species, to competitive relaxation when there was less overlap, while competitive relaxation remained the major component of the yield gain. The yield gain was substantially greater in intercrops with maize than in intercrops without maize, but there was no difference in yield gain between systems with and without legumes. The yield gain increased with nitrogen (N) input in maize/C3-cereal intercrops but not in cereal/legume intercrops, illustrating the ability of legumes to compensate for low N input, and highlighting the need for N input for high productivity in intercropping systems without legumes. Yield gain did not respond to phosphorus (P) input. We conclude that competitive relaxation is the main contributing factor to yield gain in the investigated Chinese intercropping systems, which were mostly relay strip intercropping systems. The underlying drivers of yield gain were related to presence of maize and species complementarity in time, but we did not find strong evidence for the selection effect.

Effects of strip width on yields in relay-strip intercropping: A simulation study

Intercropping is the cultivation of multiple crop species on the same land. Relay strip intercropping is an intercropping system in which the component species are grown in strips, while the growing periods of the crop species overlap only partially. The effects of strip width on yields in relay-strip intercropping are still poorly understood. Here in a case study on wheat-maize relay intercropping a simple strip intercropping model was applied to quantify intercropping performance as a function of a wide range of strip widths. Simulations showed that (1) the optimum strip width is less than 1 meter and (2) benefits of intercropping rapidly drop as strips become wider. Most previous experimental work was also done at narrow configurations, with strips less than 3 meters wide. Benefits of intercropping may therefore be less than what would be expected from experiments if narrow configurations are not attainable because of lack of mechanisation. All optimised strip configurations showed a Land Equivalent Ratio (LER) larger than 1 indicating benefits of intercropping, irrespective of assumptions that were made on radiation use efficiency in intercropped species as compared to sole crops. At current prices of wheat and maize, however, intercropping gross margin exceeded sole cropping gross margin only if the intercrop RUE was larger than sole crop RUE for both species. This study shows that strip crop growth models can be used to specify needs for future machinery, that will enable farmers to attain benefits from intercropping.

Ameliorated light conditions increase the P uptake capability of soybean in a relay-strip intercropping system by altering root morphology and physiology in the areas with low solar radiation

Belowground interspecific facilitation and complementarity contribute to the phosphorus (P) uptake advantages in the cereal-legume intercropping system. However, the root morphological and physiological plasticity and, subsequently, the P uptake capability response to light conditions in intercropping systems remain unclear. Soybean was grown under two levels of P application rates in sole and intercropping systems (maize/soybean relay strip intercropping) from 2016 to 2018 in Renshou, southwest of China. As a supplement to the field experiment, soybean was also grown in L-S (simulating the light conditions of sole cropping in the field: light first and then shading) and S-L (simulating the light conditions of intercropping in the field: shading first and then light) light conditions with two levels of P application in 2018 in a pot experiment. After maize harvest (approximately 3/4 of the soybean growth period), light capture in intercropping was higher than sole (ameliorated light conditions in intercropping system), which resulted in an advantage of P uptake in intercropped soybean. Both low P supply and more light capture increased the total root length and root APase activity. The genes GmEXPB2 (which is associated with root growth) and GmACP1 (which is associated with exudation of APase) were highly expressed in plants that captured more light under both P-sufficient and P-deficient conditions. Additionally, more light capture increased the production of lateral roots and the proportion of in the upper 15 cm soil layer roots at the reproductive stage in the field. Across the field and pot experiments, increased root morphological and physiological plasticity were associated with lower P concentrations in the leaves and greater allocation of photosynthates to roots as sucrose. It is suggested that ameliorated light conditions can regulate soybean root growth plasticity and, consequently, P uptake in maize/soybean relay strip intercropping systems, especially in the areas with low solar radiation.

Intercropping contributes to a higher technical efficiency in smallholder farming: Evidence from a case study in Gaotai County, China

Intercropping entails the concurrent production of two or more crop species in the same field. This traditional farming method generally results in a highly efficient use of land, but whether it also contributes to a higher technical efficiency remains unclear. Technical efficiency refers to the efficiency with which a given set of natural resources and other inputs can be used to produce crops. In this study, we examined the contribution of maize-based relay-strip intercropping to the technical efficiency of smallholder farming in northwest China. Data on the inputs and crop production of 231 farms were collected for the 2013 agricultural season using a farm survey held in Gaotai County, Gansu Province, China. Controlling for other factors, we found that the technical efficiency scores of these farms were positively affected by the proportion of land assigned to intercropping. This finding indicates that the potential negative effects of intercropping on the use efficiency of labour and other resources are more than offset by its higher land-use efficiency when compared with monocropping.

Shade stress decreases stem strength of soybean through restraining lignin biosynthesis

Lodging is the most important constraint for soybean growth at seedling stage in maize-soybean relay strip intercropping system. In the field experiments, three soybean cultivars Nandou 032-4 (shade susceptible cultivar; B1), Jiuyuehuang (moderately shade tolerant cultivar; B2), and Nandou 12 (shade tolerant cultivar; B3) were used to evaluate the relationship between stem stress and lignin metabolism in the stem of soybean. Results showed that the intercropped soybean was in variable light condition throughout the day time and co-growth stage with maize. The xylem area and cross section ratio played a main role to form the stem stress. The B3 both in intercropping and monocropping expressed a high stem stress with higher xylem area, lignin content, and activity of enzymes (phenylalanine ammonia-lyase (PAL), 4-coumarate: CoA ligase (4CL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD)) than those of B1 and B2. Among the soybean cultivars and planting pattern, lignin content was positively correlated with stem stress. However, a negative correlation was found between lignin content and actual rate of lodging. In conclusion, the shade tolerant soybean cultivar had larger xylem area, higher lignin content and activities of CAD, 4CL, PAL, and POD than other soybean cultivars in intercropping. The lodging in maize-soybean intercropping can be minimized by planting shade tolerant and lodging resistant cultivar of soybean. The lignin content in stem could be a useful indicator for the evaluation of lodging resistance of soybean in intercropping and activities of enzymes were the key factors that influence the lignin biosynthesis.