Productivity and land equivalent ratio of intercropping cotton with some winter crops in Egypt

Two field experiments were carried out at Research Station, El-Sharkia Governorate, ARC, Egypt during 2009/2010 and 2010/2011 seasons to inv estigate the effect of relay intercropping cotton with some winter crops as compared with sequential solid plantings of these crops on the productivity, land equivalent ratio and net return of these systems. The split plot des ign with three replications was used. Two cotton cultivars were grown in the main plots , while cropping systems were allocated in sub plots as followed: relay intercropping cotton with faba bean and wheat at 20 March, faba bean and wheat were grown with two population densities. These treatments were compared with growing cotton after Egyptian clover each of 20 th March, 20 April and 20 May, as well as, faba bean at 20 th April and wheat at 20 th May in solid plantings. Intercropping cotton with faba bean and wheat cause d significant reductions in yields of these crops. The results showed that cotton cultivar Giza 86 had igher values of seed cotton yield than Giza 90. Intercropping cotton with faba bean at 20 th March gave higher values, also it had the same effects of cotton characters grown in sequential so lid plantings at 20 th April after faba bean and after Egyptian clover at 20 th March. Intercropping cotton with wheat at 20 th March had the same values of cotton characters of traditional culture. Late planting date of cotton (20 th May) as followed after Egyptian clover or wheat caused significant reducti ons in cotton characters as compared with those grown in the early date. Low plant densities of fab a bean or wheat decreased their effects on cotton characters under relay intercropping. Also, cotton cultivars and the interactions between cotton cultivars and cropping systems had insignificant effects on yield of preceding crops ( faba bean and wheat) while cropping systems had significant effects on yield of wheat and faba bean . Solid planting of wheat in two rows/ridge (S 10) has the highest grain yield, also, solid planting of fa ba bean in high density has the highest seed yield. All intercropping systems gave advantages in LERs a s compared with sequential cropping systems where it ranged from 1.9 to 2.81 of S 2 and S4 respectively. The results revealed that cotton cultivar Giza 86 had higher values of economic retu rn han cultivar Giza 90.


INTRODUCTION
In recent years, trends in agricultural production systems have changed towards achieving high productivity and promote sustainability over time as a result of the rapid increase of the population in Egypt. It is known that Egyptian cotton (Gossypium barbadense L.) is an important crop for fiber and vegetable oil not only in Egypt but also in the world.
However, one of the main problems associated with the Egyptian farmers is escaping from growing cotton in their farms as a result of low cotton productivity after wheat harvest. To solve the problem efficiently, intercropping cotton is a promising strategy through increasing cropping index and maximizing land use. Intercropping should technically help the agricultural policy to be in the challenge against food crises in Egypt (Sayed Galal and Metwally 1986 andMetwally, 1999). Relay intercropping is a kind of intercropping systems in which two or more crops grew simultaneously during part of the life cycle. So, it may be possible that relay intercropping cotton with wheat or faba bean without tillage. So, it may be possible that relay intercropping cotton with wheat or faba bean with no tillage through modified cotton sowing dates could be increased land use and decreased fixed costs. Also, modifying in growing cotton after wheat, Egyptian clover or faba bean could be more remunerative to cotton growers.All intercropping systems with cotton have an advantage in land productivity compared to mono cultures (Zhang et al., 2007). The present study investigated the effect of cotton cultivars and cropping systems on the productivity and land equivalent ratio, as well as, net return of cotton and some winter crops.

The treatments of the study
The present investigation was carried out at Kafr EL-Hamam El-Sharkia governorate, ARC, Egypt, during the two successive seasons 2009/2010 and 2010/2011 to investigate the effect of cotton cultivars and some new cropping systems on the productivity, land equivalent ratio and net return of cotton and some winter crops. The experiment included twenty two treatments which were the combinations between two cotton cultivars and eleven cropping systems ( S 5 Relay intercropping cotton with wheat as that of system 4, but wheat was grown in three rows on the ridge (high and recommended density) S 6 Cotton was planted after three cuts of Egyptain clover at 20 th April, as that of cropping system S 1 S 7 Planting cotton after harvesting faba bean at 20 th April without tillage; wheras faba bean was grown as that of cropping system S 2 .
S 8 Planting cotton after harvesting faba bean at 20 th April without tillage; wheras faba was grown as that of cropping system S 3 .

S 9
Cotton was planted after four cuts of Egyptian clover at 20 th May.

S 10
Planting cotton after harvesting wheat at 20 th May without tillage; wheras, wheat was grown as that of cropping system S 4 .

S 11
Planting cotton after harvesting wheat at 20 th May without tillage; wheras, wheat was grown as that of cropping system S 5 . Treatments were arranged in a split plot design with three replications. Cotton cultivars were assigned to the main plots, while cropping systems were allocated in sub plots.
Each sub plot consisted of 6 ridges, 5.0 m in length, 0.7 m in width and plot area was 21.0m 2 .
Other agronomic recommended practices were practiced according to technical recommendations of cotton, wheat, faba bean and Egyptian clover. Cotton cultivars were grown by 142857 plants per ha, while faba bean was planted by 285714 plants per ha in S 3 and S 7 but density at S 2 and S 6 reduced to 142857 plants per ha. Egyptian clover was drilled by rate of 48.0 kg per ha. Wheat was planted by rate 119kg/ ha (high density) in S 5 and S 9 , while S 4 and S 8 was planted by rate 95 kg/ha. (low density). Ten individual guarded plants from cotton, faba bean and wheat were randomly taken from each experimental plot to study yield components. Seed cotton yield per ha was estimated as the weight of seed cotton yield picked from the four middle ridges in plot, then converted to yield per ha. With respect to faba bean seed yield and wheat grains per ha were estimated from the four middle ridges in sub plots and converted to yield per ha. Forage yield of Egyptian clover per ha (ton) was estimated as fresh weight of cuttings taken from the sub plot and converted to yield per ha.
The studied characters were as follows: A. Yield 1.Seed cotton yield (t/ha).
2.Yield (t/ha) of wheat and faba bean, as well as, forage yield of Egyptian clover (t/ha).

1-Land equivalent ratio (LER)
It is calculated as follows as according to (faba bean or wheat).

2-Area time equivalent ratio (ATER)
It is calculated according to Hiebsch ( Total return = (yield a x price a + yield b x price b).The prices were presented by Bulletin of Statistical Cost Production and Net Return (2013), as well as, market prices.

Net return / ha (L.E.).
Net return / ha = total return -variable costs for both crops in solid and intercropping patterns.

D. Statistical manipulation
The data were statistically analyzed according to the technique of analysis of variance (ANOVA) for the split plot design using COSTAT Computer software package. Least Significant Difference (LSD) was used to test the differences between treatment means at 5% level of probability as described by Gomez and Gomez (1984). The homogeneity test was conducted of error mean squares and accordingly, the combined analysis of the two experimantal seasons was carried out.

Cotton cultivars
Seed cotton yield was affected significantly by the two cotton cultivars in the combined data across 2010 and 2011 seasons (Table 2). In all cropping systems, cotton cultivar Giza 86 had higher seed cotton yield than Giza 90. These may be due to some varietal differances of each cultivar which formed its canopy could be interacted with the environmental conditions that reflected finally on seed cotton yield (Table 2).
So, it is known that differing cotton leaf shapes with varying lobing cause large alterations in the structure of the plant canopy and its ability to intercept light (

2.Cropping systems
Seed cotton yield was affected significantly by cropping systems (Table 2). Growing cotton with faba bean by relay intercropping system at 20 th March or sequential double cropping system at 20 th April gave significant increases in seed cotton yield as compared to the corresponding cropping system of wheat. Also, low density of faba bean (S 2 ) caused insigificant increment of cotton production (compare between S 2 and S 3 ) These results could be due to the reduction of inter and intra-specific competition between the two species for basic growth resources in relay intercropping cotton with faba bean as compared with those of wheat. Also, it seems that faba bean and Egyptian clover Growing cotton with wheat increased inter and intra-specific competition between the two species for basic growth resources i.e. light, water and nutrients from the sowing cotton at 20 th March, until harvesting wheat at 20 th May. During this period (about 8 weeks), shading of wheat had adverse effects on cotton plants. This effect was increased by incraesing plant density of wheat from two to three rows per ridge. Increasing plant density of wheat may be increase soil nutrients defeciency through its allelopathic effects for cotton growth and development compared with low density (S 4 and S 8 ). Also, three rows of wheat per ridge allowed lower light transmission inside cotton canopy than two wheat rows. Relay intercropping cotton with wheat at 20 th March increased seed cotton yield significantly as compared with sequential double cropping system of cotton after Egyptian clover and wheat at 20 th May, these may be due to longer period of vegetative growth during normal environmental conditions to produce more dry matter accumulation through photosynthesis process from stem elongation stage to pollination process as compared with the late date of 20 th May.

Respone of the interaction between cotton cultivars and cropping systems
Seed cotton yields per plant and per ha were affected significantly by the interaction between the two cotton cultivars and cropping systems (Table 2). Relay intercropping cotton cultivar Giza 86 with low density of faba bean gave the highest value of seed cotton yield than other systems. Also, cotton cultivar Giza 86 recorded higher seed cotton yields than the other cultivar in all cropping systems except growing it in sequential systems at 20 th May after wheat or Egyptian clover. These results revealed that cotton cultivar Giza 90 was more tolerant to delaying sowing date than cultivar Giza 86.

B. Yield of wheat grains and faba bean seeds 1. Cotton cultivars
There were no significant effects ofcotton cultivars on the productiviy of winter crops (wheat and faba bean).

Cropping systems -Productivity of wheat crop
Grain yield of wheat were affected significantly by cropping systems (Table 3) With regard to wheat plant densities, there were no significant differences between high and low densities under solid or intercropping systems. -

Productivity of faba bean crop
Seed yield was decreased significantly under intercropping culture (S 2 ) and (S 3 ) as compared to solid ones, (S 7 and S 8 ). These results may be due to the competition between cotton and faba bean plants for light, nutrients and available water (Table 3).
With respect to faba bean plant densities, seed yield was higher by doubling plant density of faba bean (on both sides) under solid and intercropping cultures (S 3 and S 8 ) than low plant densities (one side). The increasing in seed yield was quite expected as a result of

Respone of the interaction between cotton cultivars and cropping systems
The interaction between cotton cultivars and cropping systems had no significant effects on grain yield of wheat, as well as, faba bean seed yields (Table 3). -

Productivity of Egyptian clover
In Egypt, cotton and Egyptian clover are grown in sequential solid cropping system at different planting dates for cotton from March to May. Forage yield of Egyptian clover recorded 26.19, 41.65 and 57.12 t/ha of cropping systems (S 1 , S 6 and S 9 ), respectively, as a result of increasing number of cuts and growing cycles (Table 3).

Land equivalent ratio (LER)
Relative yield of intercropping cotton with faba bean or wheat was affected significantly by cotton cultivars (Table 4). Cotton cultivar Giza 86 had higher values of relative seed cotton yield than the cultivar Giza 90.
Relative seed cotton yield of relay intercropping cotton with faba bean was increased significantly than that of sequential cropping system (compare systems S 2 and S 3 with system S 8, Table 4) where it reached +8%. The corresponding values of intercropping cotton with wheat was increased to 178 % as compared by sequential doubling cropping system (100%), (compare systems S 4 and S 5 with system S 11 ). These increments were due to long period of vegetative growth during normal environmental conditions to produce more dry matter accumulation and yield production.
Also, relative seed cotton yield of intercropping cotton with low densities of faba bean or wheat in S 2 and S 4 systems had higher values as compared to high densities of these crops at S 3 and S 5 systems. These results may be due to little competition effects at low densities of faba bean and wheat with cotton plants.
In regard to relative yields of winter crops (faba bean and wheat), relative yield of faba bean and wheat did not affect significantly by cotton cultivars (Table 4). Relative yield of faba bean was decreased significantly +20% by relay intercropping with cotton than that of sequential double cropping system (S 2 and S 3 with S 8 ).
On the other hand, relative yield of wheat did not differ significantly by relay intercropping cotton as compared to solid culture (S 4 and S 5 with S 11 ).  Values of LERs were estimated by using data of relay intercropping compared with solid double cropping systems of those crops (Table 4). LER was not affected significantly by cotton cultivars in case of faba bean. But the converse was true with wheat (Table 4). Cotton cultivar Giza 86 had higher values of LER than those of cultivar (Giza 90).
With respect to faba bean, LER was decreased significantly +10% by intercropping cotton with faba bean (S 2 and S 3 ) as compared to sequential double cropping system (S 8 ).
In regard to intercropping cotton with wheat, LER increased significantly +74% than that of sequential double cropping system "S 11 " (Table 4) LER was not affected significantly by the interaction between cotton cultivars and cropping systems in case of faba bean but the converse was true with wheat. LER was decreased more by intercropping cotton cultivar Giza 86 with high plant density of wheat (S 5 ) as compared with cotton cultivar Giza 90.

2-Area time equivalent ratio (ATER)
Results of ATER were calculated according to Hiebsch and McCollum (1987). Values of ATER were less than LER. With respect to faba bean crop, ATER was not affected significantly by cotton cultivars (Table 5). But it was affected significantly by cropping systems (Table 5). In general, intercropping cotton with faba bean (S 2 and S 3 ) had higher values of ATER compared to sequential double cropping system (S 8 ). This mean that yield advantage was produced and land usage efficiency increased by intercropping cotton with faba bean by 4%. ATER was influenced significantly by the interaction between cultivars and cropping systems. With respect to intercropping cotton with wheat, values of ATER were affected significantly by cotton cultivars, cropping systems and the interaction between them. Giza 86 had higher values than Giza 90 (Table 5). Intercropping cotton with two rows of wheat (low density, S 4 ) had higher ATER values as compared to cropping systems (S 5 and S 11 ) whereas it reached 1.69%. These results may be due to decreasing inter and intra-specific competition between the two species (cotton + wheat) and the same species (wheat), respectively, for basic growth resources (nutrients, water and solar radiation)

D. Economic performance
The results revealed that cotton cultivar Giza86 had higher values of total and net returns than cotton cultivar Giza 90. In regard to cropping systems, total and net returns of intercropping cotton after faba bean gave higher values of total and net returns (Tables 6 and   7); while, planting cotton at 20 th May harvesting gave lower values in total and net return, i.e.
4609.0 and 4423.0, and 1144.0 and 1454.0 USD /ha in S 11 and S 9, respectively.

CONCLUSION
The finding of this study is useful to increase cotton production in Egypt by using new cropping systems such as relay intercropping cotton with faba bean and wheatat 20 th March and planting cotton after faba bean at 20 th April. These cropping systems produced high production of seed cotton with good quality, in addition to the increases of land equivalent ratio and economic return. These new cropping systems will be encourged Egyptian farmers to grow cotton in their fields.