Intercropping, the agricultural practice of cultivating two or more crops in the same space at the same time, is an old and commonly used cropping practice which aims to match efficiently crop demands to the available growth resources and labor. The most common advantage of intercropping is the production of greater yield on a given piece of land by making more efficient use of the available growth resources using a mixture of crops of different rooting ability, canopy structure, height, and nutrient requirements based on the complementary utilization of growth resources by the component crops. Moreover, intercropping improves soil fertility through biological nitrogen fixation with the use of legumes, increases soil conservation through greater ground cover than sole cropping, and provides better lodging resistance for crops susceptible to lodging than when grown in monoculture. Intercrops often reduce pest incidence and improve forage quality by increasing crude protein yield of forage. Intercropping provides insurance against crop failure or against unstable market prices for a given commodity, especially in areas subject to extreme weather conditions such as frost, drought, and flood. Thus, it offers greater financial stability than sole cropping, which makes the system particularly suitable for labor-intensive small farms. Besides, intercropping allows lower inputs through reduced fertilizer and pesticide requirements, thus minimizing environmental impacts of agriculture. However, intercropping has some disadvantages such as the selection of the appropriate crop species and the appropriate sowing densities, including extra work in preparing and planting the seed mixture and also extra work during crop management practices, including harvest. The selection of an appropriate intercropping system for each case is quite complex as the success of intercropping systems depend much on the interactions between the component species, the available management practices, and the environmental conditions. Plant breeding can contribute determinedly to increase of productivity of intercropping systems by investigating and exploiting the genetic variability to intercrop adaptation. This paper provides an overall view and evaluation of annual intercropping, summarizing its main advantages supported by a number of key examples from the literature which point out its great value in the context of sustainable agriculture.

/pdf/annual-intercrops-an-alternative-pathway-for-sustainable-fh12loak0h.pdf

Annual intercrops: an alternative pathway for sustainable agriculture.

Interspecific competition, n use and interference with weeds in pea-barley intercropping

Pea-barley intercropping for efficient symbiotic N2-fixation, soil N acquisition and use of other nutrients in European organic cropping systems

The effect of sole and intercropping of field pea (Pisum sativum L.) and spring barley (Hordeum vulgare L.) and of crop residue management on crop yield, NO3- leaching and N balance in the cropping system was tested in a 2-year lysimeter experiment on a temperate sandy loam soil. The crop rotation was pea and barley sole and intercrops followed by winter-rye and a fallow period. The Land Equivalent Ratio (LER), which is defined as the relative land area under sole crops that is required to produce the yields achieved in intercropping, were used to compare intercropping performance relative to sole cropping. Crops received no fertilizer in the experimental period. Natural 15N abundance techniques were used to determine pea N2 fixation. 
The pea-barley intercrop yielded 4.0 Mg grain ha-1, which was about 0.5 Mg lower than the yields of sole cropped pea but about 1.5 Mg greater than harvested in sole cropped barley. Calculation of the land equivalent ratio showed that plant growth resources were used from 17 to 31% more efficiently by the intercrop than by the sole crops. Pea increased the N derived from N2 fixation from 70% when sole cropped to 99% of the total aboveground N accumulation when intercropped. However, based upon aboveground N accumulation the pea-barley intercrop yielded about 85 kg N ha-1, which was about 65 kg lower than sole cropped pea but about three times greater than harvested in sole cropped barley. Despite different preceding crops and removal or incorporation of straw there was no significant difference between the subsequent non-fertilized winter-rye grain yields averaging 2.8 Mg ha-1 Indicating an equalization of the quality of incorporated residue by the NO3- leaching pattern. NO3- leaching throughout the experimental period was 61 to 76 kg N ha-1. Leaching dynamics indicated differences in the temporal N mineralization comparing lysimeters previously cropped with pea or with barley. The major part of this N was leached during autumn and winter. Leaching tended to be smaller in the lysimeters originally cropped with the pea-barley intercrops although not significantly different from the sole cropped pea and barley lysimeters. Soil N balances indicated depletion of N in the soil-plant system during the experimental period, independent of cropping system and residue management. N complementarity in the cropping system and the synchrony between residual N availability and crop N uptake is discussed.

The comparison of nitrogen use and leaching in sole cropped versus intercropped pea and barley

Root system dynamics, productivity and N use were studied in inter- and sole crops of field pea (Pisum sativum L.) and spring barley (Hordeum vulgare L.) on a temperate sandy loam. A 32P tracer placed at a depth of 12.5, 37.5, 62.5 or 87.5 cm was employed to determine root system dynamics by sampling crop leaves at 0, 15, 30 and 45 cm lateral distance. 15N addition was used to estimate N2 fixation by pea, using sole cropped barley as reference crop. The Land Equivalent Ratio (LER), which is defined as the relative land area under sole crops that is required to produce the yields achieved in intercropping, were used to compare the crop growth in intercrops relative to the respective sole crops. The 32P appearance in leaves revealed that the barley root system grows faster than that of pea. P uptake by the barley root system during early growth stages was approximately 10 days ahead of that of the pea root system in root depth and lateral root distribution. More than 90% of the P uptake by the pea root system was confined to the top 12.5 cm of soil, whereas barley had about 25–30% of tracer P uptake in the 12.5 – 62.5 cm soil layer. Judging from this P uptake, intercropping caused the barley root system to grow deeper and faster lateral root development of both species was observed. Barley accumulated similar amounts of aboveground N when grown as inter- and sole crop, whereas the total aboveground N acquired by pea in the intercrop was only 16% of that acquired in the pea sole crop. The percentage of total aboveground N derived from N2 fixation in sole cropped pea increased from 40% to 80% during the growth period, whereas it was almost constant at 85% in intercropped pea. The total amounts of N2 fixed were 95 and 15 kg N ha−1 in sole cropped and intercropped pea, respectively. Barley was the dominant component of the pea-barley intercrop, obtaining 90% of its sole crop yield, while pea produced only 15% of the grains of a sole crop pea. Intercropping of pea and barley improved the utilization of plant growth resources (LER > 1) as compared to sole crops. Root system distribution in time and space can partly explain interspecific competition. The 32P methodology proved to be a valuable tool for determining root dynamics in intercropping systems.

Temporal and spatial distribution of roots and competition for nitrogen in pea-barley intercrops – a field study employing 32P technique

http://directory.umm.ac.id/Data%20Elmu/jurnal/E/European%20Journal%20of%20Agronomy/Vol12.Issue2.March2000/3.pdf

Intercropping corn with soybean, lupin and forages: yield component responses

Intercropping corn with soybean, lupin and forages: weed control by intercrops combined with interrow cultivation

Intercropping of corn with legumes is an alternative to corn monocropping and has a number of advantages, for example, lower levels of inputs, lower cost of production and better silage quality than monocrop systems. An experiment was carried out at two sites in 1993 and 1994 to investigate the effects of seeding soybean or lupin alone or in combination with one of three forages (annual rye-grass, Lolium multiflorum Lam.; perennial ryegrass, Lolium perenne L.; red clover, Trifolium pratense L.) on silage yield and quality. The intercrop plots received 90 kg ha -1 less nitrogen fertilizer than monocrop plots, which received 180 kg ha -1 . Corn biomass yield had a variable response to the treatments, but showed no change at most site-years. Soybean and lupin biomass yields were decreased by intercropping (80-98 % for soybean, and 94-100 % for lupin). However, when corn growth was limited due to poor establishment at one site in 1994, soybean was able to grow well and produce yields similar to those of monocropped soybean. The three underseeded forages did not grow well during the period examined (up to silage harvest) and had no effect on the yield of any crop. Total silage yields were similar to corn monocrop biomass yields even during 1994 at the site with low corn population densities because soybean was able to compensate for reduced corn growth.

Intercropping of Corn with Soybean, Lupin and Forages: Silage Yield and Quality

Intercropping of corn with legumes is an alternative to corn monocropping and has a number of advantages, for example, lower levels of inputs, lower costs of production and better silage quality than the monocrop system. An experiment was carried out at two sites in 1993 and 1994 to investigate the effects of seeding date (simultaneous with corn or 3 weeks later) and number of rows of large-seeded legumes (one or two) seeded between the corn rows. The intercrop plots received 90 kg ha−1 less nitrogen fertilizer than the monocrop plots, which received 180 kg ha−1. Silage yields were sometimes decreased by the simultaneous seeding of corn and large-seeded legumes. Protein content and concentration were not affected by most treatments and provided reasonable quality silage, despite a reduction in the amount of nitrogen fertilizer used.

Zusammenfassung

Mischanbau von Mais mit Leguminosen ist eine Alternative fur den Reinanbau von Mais und hat eine Anzahl von Vorteilen, z. B. geringere Bestellungskosten, geringere Kosten der Produktion und eine bessere Silagequalitat als der Reinanbau. Es wurde ein Experiment auf zwei Standorten in den Jahren 1993 und 1994 durchgefuhrt, um den Einfluss des Aussaatdatums (gleichzeitig mit Mais oder drei Wochen spater) sowie im Hinblick auf die Anzahl der Reihen zwischen den Maisreihen mit grosikornigen Leguminosen (1 oder 2) untersucht. Die Mischanbauparzellen erhielten 90 kg ha−1 weniger Stickstoffdunger als die Reinbestande, die 180 kg ha−1 erhielten. Die Silageertrage waren etwas verringert bei einer gleichzeitigen Aussat von Mais und Leguminosen. Eiweisigehalt und -konzentration waren durch die meisten Behandlungen nicht beeintrachtigt und ergaben ausreichende Qualitat der Silage trotz einer Reduktion in der verwendeten Stickstoffdungermenge.

Q. Fe

Papers

Intercropping corn with soybean, lupin and forages: yield component responses

Intercropping corn with soybean, lupin and forages: weed control by intercrops combined with interrow cultivation

Intercropping of Corn with Soybean, Lupin and Forages: Silage Yield and Quality

Intercropping of corn with soybean and lupin for silage : Effect of seeding date on yield and quality