Improvement of lettuce growth and yield with

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number, stem fresh weight, stem dry matter and total yield. ..... Effect of mulching with various films on the yield quality of butterhead lettuce and celery stalks.
International Journal of Agriculture and Crop Sciences. Available online at www.ijagcs.com IJACS/2013/6-16/1137-1143 ISSN 2227-670X ©2013 IJACS Journal

Improvement of lettuce growth and yield with spacing, mulching and organic fertilizer Iraj khazaei1, Reza Salehi2, Abdolkarim Kashi2 and Seyed Mohammad Mirjalili1 1. Department of Horticultural Sciences, Faculty of Agriculture and Natural Resources, Islamic Azad University, Karaj Branch, Iran 2. Department of Horticultural Sciences, Campus of Agriculture and Natural Resources, University of Tehran, Karaj, 31587-77871, Iran Corresponding author: Iraj khazaei ABSTRACT: The experiment was conducted in a field in Karaj-Iran to find out the effects of spacing, mulch and organic fertilizer on the growth and yield of lettuce.Four levels of spacing (40×40 cm, 40×35 cm, 40×30 cm and 40×25 cm),two cultivation systems(mulch and nomulch) and two different types oforganic fertilizers (humic acid and vitamint) were conducted onLactuca sativa cv. Iceberg at the Engineer Zeraee’s field.The treatmentswere set up ina split plot factorial design based on the randomized complete block design with three replications.According to results of experiment, plantspacingshowed significant effects onstem diameter, stem weight, stem fresh weight, stem dry matter, leaf number, stem dry weight, leaf dry weight, total yield, NO3 %, P %and K%. Mulching had significant effects on stem length, stem diameter, stem weight, head diameter, leaf number, bud number, stem fresh weight, stem dry matter and total yield. Also stem length, stem diameter, stem weight, bud number, leaf dry weight and K%were significantly affected by organic fertilizer. The highesttotal yield of lettuce was obtained from spacing 40×35 cm and the lowest observed in spacing 40×40. Although vitamint showed better effect on lettuce growth, organic fertilizer hadn’t significant effect on total yield. Finally, total yield increased with mulch application compare with no mulch treatment. Keywords: Lactuca sativa, Spacing, Mulching, Humic acid, Vitamint. INTRODUCTION Lettuce (Lactuca sativa), an annual plant ofAsteraceaefamily,is one of the most important vegetables in human diet.The plant is full of vitamins and minerals with lots of fiber which facilitates colon peristalsis. Lettuce th is 26 among 39 vegetables and fruits of nutrition value and is fourth of consumption. It ‘s the most popular salad crop in the world and because of used crude, its vitaminsinter to human body without change. Iran ranks th th 9 country in the world for lettuce production and 11 for area culture (FAO, 2009). Soil health is a crucial factor for realizing higher yield of vegetables. Excessive application of chemical fertilizers may affect soil health and sustainable productivity (VirgineTenshia and Singram, 2005).Organic farming is appreciated by vegetable consumers as it enhances quality of the produce. Today the people are preferred to get the vegetable without the inorganic fertilizer, because they are suffering with some serious diseases which are due to the effects of chemical fertilizer (Asaduzzaman et al., 2010). To decrease chemical fertilizer’s harmful effects, some organic matter is used. Humic acid (HA) is a heterogeneous mixture of many compounds of organic materials arising from the remains of plant and animal residues,generally with similar chemical properties(MacCarthy et al., 2001). Due to increasing cell membrane permeability, oxygen uptake,respiration, photosynthesis, phosphorus uptake and supplying root cell growth, it performs various functions on the plant growth (Ameri and Tehranifar 2012, Gulser et al., 2010).Humic compounds have beneficial effects onsoil physiochemical properties include stabilizationof soil structure (Piccolo and Mbagwu,1990) and increasingcation exchange (Allison,1973).Also,humic acid increases population of soli microorganisms, especially in the surface layer of root rhizosphere, that create substances which stimulate plant growth (Awad, 2002).In many studies, humic preparations were reported to increase the uptake of mineral elements (Maggioniet al. 1987; Mackowiaket al. 2001), to promote the root length (Vaughan & Malcolm 1979) and to increase the fresh and dry weights of crops (Chen et al. 2004). During crop growth a number of factors may affect vegetable quality and quantity. Improving the growth factors is crop quality and quantity key. Thus growers need to increase their production by adoptingappropriate strategies and techniques which will lead tosufficient and reliable yields without depleting the naturalresource

Intl J Agri Crop Sci. Vol., 6 (16), 1137-1143, 2013 base.Within the several techniques used in lettucecultivation, the use of mulches is known to be worthwhile,being an important reason for the crop’s quality and productivity improvement (FontanettiVerdial et al. 2001). Mulch is a natural (straw, sawdust, herbage and other materials) or synthetic (polyethylene in different color) material which is used for protection of plant from chilling, drought and other perquisites. Also, it is considered as an agrotechnical procedure which can significantly modify microclimate around plants (Siwek et al. 2007). This treatment not only leads to improving crop quality and quantity, but also its application results in decreasing moisture lost from the soil surface, inhibitingweed growing, decreasing pest populationsand preventingsoil temperature changes(Preece and Read 1993, Splittstoesser1990) Plant spacing is one the factors that can affect vegetable quality and quantity. Optimum plant density ensures the plants to grow uniformly and properly through efficient utilization of moisture, nutrients, light and thus causes to produce maximum yield of lettuce (Firoz et al. 2009).With regard to the importance of humic acid,mulches and plant spacing on the quality and quantity of plants,this study was carried out to determine humic acid and vitaminteffects on lettuce and establish the optimum spacingand mulch which provide the optimum yieldfor use as a vegetable. MATERIAL AND METHODS Field experiment Research with lettuce was conducted in 2010 at thetown Engineer Zeraee’s filed, placed in Karaj, Iran (50.56º W longitude, 47.35ºN latitude and 1261.1 m altitude). At the beginning of study, some physical and chemical characteristics of the soil at the depth of 20 cm were analyzed (Table 1). Table 1.Some physical and chemical properties of the soil of experimental field. Soil properties Textural class EC (ds.m-1) pH Total nitrogen (%) K (ppm) P (ppm) Zn (ppm) Fe (ppm)

Analytical value Clay loam 0.62 7.6 2.5 247.8 28 1.8 8

The treatments of theexperiment comprised of four different plant spacing (40×40 cm, 40×35 cm, 40×30 cm and 40×25 cm),two cultivation systems(mulch and no mulch) and two different types of organic fertilizer (humic acid and vitamint). A split plot factorial design based on the randomized complete blockdesign with three replications was served in this study, where mulching was given in main plot, organic fertilizer and plant spacing in sub-plot.The unit plot size was 3×1.2 m and in total, 48 plots were considered.Lettuce seed cv. Iceberg was prepared from Niagara Company and the seeds were planted into coco-peat mediain tray (on May, 2) and maintained in greenhouse until they formed 3-4 leaves, then transferred to the field (on June, 2). Irrigation pipes, including 20 cm droppers with 40 cm distance from each other, were placed in the field. Silver polyethylene mulches were covered on half of plots and others haven’t mulch, then cave a hole for seedling culture with 40 cm intervaland different plant spaces in each treatment(25, 30, 35 and 40 cm). The plants were -1 fertilized at one month after transplanting, using the spray. Vitamint fertilizer (6 lit.ha ) used on half of plots and -1 others used humic acid(10 lit.ha ).During the growing period, the plants were weekly irrigated. Sampling and traits analysis Four plants were selected atrandomfromeachunit plot on theJuly22th (50 days after transplanting).Following parameters were recorded from the mean of four harvested sample plants: stem length and diameter, number of leaf, number of bud, fresh and dry weightsof stem, fresh and dry weights of leaf, head weight and diameter and total yield.TotalP and K contents of leaves were determined for each treatment according to atomic absorption spectrophotometric (Helrich, 1990) methods.Nitrate accumulation in lettuce leaves was measured by the cadmium reduction method,utilizing a water extract with a spectrophotometric method of analysis (Hach, 2006).Data of all measured parameterswere analyzed statistically by SAS statistical software.Also,Duncan’s Multiple Range Tests (DMRT) was used to compare treatment means at a probability level of 0.05. RESULT AND DISCUSSION Spacing The results of the present study showed that the effects of different spacing treatments on stem diameter, stem fresh and dry weights, leaf dry weight, leaf number, total yield, NO3 %, P % and K% were

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Intl J Agri Crop Sci. Vol., 6 (16), 1137-1143, 2013 significant (Table 2).Stem diameter was increased with increase in spacing up to 40×35 (5.61 cm), but no further increase was observed in 40×40.Stem fresh weight indicated difference between spacing treatment and the highest value was achieved in 40×25 spacing (51.8 gr).Spacing significantly increased the dry weight of stem, as it was maximum at 40×40 spacing(5.29 gr).On the contrary, the highest number of leaves was observed in 40×30 spacing and the lowest was observed in 40×40 spacingand leaf dry weight were obtained in -1 40×30 spacing (32.6 and 11.79 gr, respectively).Total yield of lettuce was the highest (61.318 ton.ha ) in 40×35 spacing.Also, the highest percentage of NO3 was obtained in 40×35 spacing and the highest percentage of K was achieved in 40×30spacing (Table 3). Our total yield result was in confliction with Moniruzzaman (2006). He explained the significant increase in yield at closerspacing (40×20) over wider spacing may solely be ascribed on the function of the highest plant density per unitarea of land. The purpose of this study was to determine the minimum plant spacing thatcould be tolerated without yield or qualityloss under field conditions. Tawaha et al. (2005) studied spacing effect on chickpea and reported that pod number increased with increased density due to plant competition for light and nutrition. On the other hand when the spacing is decreased, unit area and nutrition for each plant is decreased so plant doesn’t have enough growth and branch and pod number will decrease. The improper plant spacing may cause either too dense or too sparse population resulting in the reduction of lettuce yield (Firoz et al., 2009). Our result was in agreement with Sadeghi et al. (2009), Aminifard et al. (2010), Mengistu and Yamoah (2010) and Gomez and Oberpaur (2007). They found that spacing affected significantly lettuce yield and growth factors. High spacing decrease yield with low plant density and low spacing decrease yield with plant competition with each for light, water, nutrition and other growth requirements. Mulch stem length, stem diameter, fresh and dry weights of stem, head diameter, leaf number, bud number, and total yield of lettucewere significantly increased by mulching, but fresh and dry weights of leaf, head weight, stem dry matter and NO3, total P and K contents of leaves were not affected(Table 2).As can be seen, the highest values of stem length, stem diameter, fresh and dry weights of stem, head diameter, leaf number, bud -1 number, and total yield (12.25 cm, 5.6 cm, 45.33 gr, 5.24 gr, 12.63 cm, 31.7, 7.39, 60.836 ton.ha , respectively) were obtained from mulching treatment (Table 3). FontanettiVerdial et al. (2001) studied on effect of mulch on Iceberg lettuce. They mentionedblack plastic mulchand double-faced plastic mulch (silver/black) had the highest averages ofchlorophyll, head weight and dry matter ofhead.The double-faced plastic mulch had the highest average for the nitrogen concentration in the aerial part of the plant. Also the double-faced plastic mulch promoted higher average values for the total amounts of N, P, S, B, and Fe, due to a higher dry matter weight in the plants with these treatments.Finally they explained that the treatments without mulch had lower average values for total quantities of nutrients when compared to the treatments using plastic mulch. Jenni et al., (2004) showed that polyethylene or paper mulches with at least one black side were effective in controlling weed growth and also they reported that growing lettuce on paper or polyethylene mulches increased marketable yield (7%) and resulted in significantly heavier heads compared with the control. Our result showed that mulching hadnot effect on NO3 concentration. But in contrary Wojciechowska et al. (2007) mentioned that mulching with transparent and white film, regardless of the material the film was made from, had a significant effect on decreasing nitrate content in lettuce heads in comparison with the control treatment. Totally mulching causes better nutrition absorption, weed control and temperature adjacent in crown and improved growth and due to them total yield increased. Organic fertilizer The application of organic fertilizer had a significant effect on stem length as well as stem diameter, head weight, bud number and K% (Table 2). The stem length, stem diameter andbud number were greater in the plants fertilized with vitamint (12.37 cm, 5.62 cm and7.52, respectively) than the humic acid treatment, however percentage of K of leaf was the highest with the humic acid fertilization (Table 3). Hochmuth (1998) reported that Megafol spray treatments had not effect on lettuce yields, head size, firmness, tip burn and internal stem length.Also early lettuce growth, early plant vigor and lettuce leaf nutrient concentration at harvest were not affected by Megafol sprays.Masarirambi et al. (2010) studied on effect of organic fertilizer (bounce back compost, cattle manure and chicken manure)and inorganic fertilizer on lettuce yield and quality. They found that type of fertilizer significantly affected growth, yield and nutritional quality of lettuce. The chicken manure exhibited relatively higher values on number of leaves, plant height, marketable yield and mean leaf dry mass.

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Intl J Agri Crop Sci. Vol., 6 (16), 1137-1143, 2013 Cattle manure was second, and then bounce back compost and lastly the inorganic fertilizers.Mohammadipour et al. (2012) performed a study on marigold and they showed that the effect of humic acid treatments on number of leaves and flowers, dry weight and plant height was significant. As previous mentioned Humic acid is a commercial product containing abundant nutrients improves soilfertility and increase the availability of nutrients to plants and thus it influences plant growth and yield and in Table 3showed that increased K % in plant but hadn’t effect on P and NO3 content in plant. Interaction effects The interaction between spacing and organic fertilizer was significant for the head diameter, leaf number and NO3 %.Interaction effect of spacing and mulching onP and K contents of lettuce leaf were significant.Also, head diameter, NO3 % and K % were affected significantly by interaction effect of mulching and Organic fertilizer. Finally, interaction between spacing, mulching and Organic fertilizer was significant only for NO3 % (Table 2).Results ofinteraction of treatment for some traits were different with main effects of treatments. CONCLUSION Based on the results, there were significant differences on the different plant spacing, mulch application and different types of organic fertilizer as statistically analyzed. It was observed that lettuce grown in 40×35 spacing, no mulch application and vitamint fertilizer performed thebest result for NO3 which was significantly affected by spacing, mulching and Organic fertilizer among the other treatment combination used for this experiment. As we know higher nitrate percentage is negative attribute and caused NO3 accumulation but it can promote vegetative growth. The best result for total yield observed by 40×35 spacing and mulch application. It is however, recommended that further investigation be evaluated across different locations with varied soil types. Table 2. Variance analyses for the lettuce traits. Source of variation

Degree of freedom

Block Spacing Mulch Spacing×Mulch Organic fertilizer Spacing×Organic fertilizer Mulch×Organic fertilizer Spacing×Mulch×Organic fertilizer Error CV

2 3 1 3 1 3 1 3 16

Stem length (cm) 7.27 ns 5.49 ns 42 ** 1.37 ns 54.4** 8.04 ns 8.75 ns 1.25 ns 4.11 17.9

Stem diameter (cm) 1.5 ns 1.44 ** 3.85** 0.42 ns 4.56** 0.36 ns 0.1 ns 0.1 ns 0.27 9.79

** significant at 0.01 and * at 0.05;

Stem fresh weight (gr) 6.84 ns 558.4** 516.7** 112.6 ns 3.79 ns 26.6 ns 4.87 ns 34.08 ns 55.13 17.65 ns

Stem dry weight (gr) 0.5 ns 3.63* 10.1** 0.89 ns 0.22 ns 0.98 ns 0.22 ns 0.62 ns 0.8 19.58

Head weight (gr) 8171.5 ns 13071.4 ns 38250.5ns 2301.5 ns 8453.5 ns 4116.9 ns 196.02 ns 4379.5 ns 10570.1 16.9

Head diameter (cm) 2.37 ns 11.15 ns 28.49 * 9.07 ns 5.08 ns 14 * 15.43 * 4.9 ns 4.1 17.07

Number of leaf 109.7 ns 67.8 * 161.3 ** 5.38 ns 56.3 ns 38.9 * 30 ns 7.47 ns 13.52 12.3

not significant

Table 2. Variance analyses for the lettuce traits. (Continue) Source of variation Block Spacing Mulch Spacing×Mulch Organic fertilizer Spacing×Organic fertilizer Mulch×Organic fertilizer Spacing×Mulch×Organic fertilizer Error CV

Degree of freedom 2 3 1 3 1 3 1 3 16

Number of bud 0.1 ns 0.6 ns 8.75 * 2.19 ns 14.6 ** 0.96 ns 0.005 ns 1.44 ns 1.07 1.03

Leaf fresh weight(gr) 9086.3 ns 31574.4 ns 24286.9 ns 2170.1 ns 8552.01 ns 4763 ns 26531.5 ns 6265.2 ns 10353.3 24.46

Leaf dry weight (gr) 97.9 ns 336.9 * 208.8 ns 45.3 ns 60.22 ns 60.65 ns 110.6 ns 3.82 ns 77.03 18.05

Yield (ton.ha-1) 59214 ns 60148 * 58990 * 60800 ns 60150 ns 61174 ns 59324 ns 60217 ns 60070 12.4

NO3 (%)

P (%)

K (%)

0.14 ns 57.8 ** 0.01 ns 0.009 ns 0.16 ns 0.5 ** 0.2 * 0.42 ** 0.05 8.89

0.01 ns 0.33 ** 0.0001 ns 0.49 ** 0.09 ns 0.03 ns 0.01 ns 0.07 ns 0.06 4.87

0.00005 ns 0.003 * 0.001 ns 0.002 * 0.1 ** 0.0003 ns 0.005 * 0.001 ns 0.0009 5.29

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Intl J Agri Crop Sci. Vol., 6 (16), 1137-1143, 2013 ** significant at 0.01 and * at 0.05;

ns

not significant.

Table 3. The effects of spacing onlettuce traits. Treatmens

Stem lengh (cm)

Spacing 25×40 10.54 a 30×40 12.19 a 35×40 11.29 a 40×40 11.23 a Mulching No Mulch 10.37 b Mulch 12.25 a Organic fertilizer Humi acid 10.25 b Vitamint 12.37 a

stem diameter (cm)

Stem fresh weight (gr)

Stem dry weight (gr)

Head diameter (cm)

Leaf fresh weight (gr)

Leaf dry weight (gr)

4.86b 5.23 ab 5.61 a 5.56 a

51.8 a 40.6 b 51.13 a 50.7 a

4.24 b 4.37 b 5.23 a 5.29 a

10.83 a 13.13 a 11.53 a 11.95 a

491.6 a 402.04 b 390.9 b 379.2 b

37.02 b 35.4 b 46.7 a 47.04a

5.02 b 5.6 a

38.77 b 45.33 a

4.33 b 5.24 a

11.09 b 12.63 a

393.4 a 438.4 a

46.52 a 50.69 a

5.01 b 5.62 a

42.33 a 41.77 a

4.85 a 4.72 a

12.18 a 11.53 a

429.3 a 402.6 a

47.49 a 49.73 a

For the same variable, means with different letters were significantly different at the 5% level as determined by Duncan’s multiple range test (DMRT). Table 3. The effects of spacing onlettuce traits. (Continue) Treatmens

Number ofleaf

Spacing 25×40 28.2 bc 30×40 32.6 a 35×40 31 ab 40×40 27.5 c Mulching No Mulch 28.04 b Mulch 31.7 a Organic fertilizer Humi acid 28.7 a Vitamint 30.95 a

Number of bud

Yield (ton.ha-1)

NO3 (%)

P (%)

K (%)

6.66 a 7a 7.2 a 7a

56.416 b 56.325 b 61.318 a 53.872 c

2.57 b 2.76 ab 2.93 a 2.58 b

5.04 b 5.34 a 5.45 a 5.3 a

0.54 b 0.59 a 0.56 ab 0.56 ab

6.54 b 7.39 a

55.843 b 60.836 a

2.73 a 2.69 a

5.28 a 5.28a

0.56 a 0.57 a

6.41 b 7.52 a

60.514 a 60.311 a

2.65 a 2.77 a

5.33 a 5.24 a

0.58 a 0.54 b

For the same variable, means with different letters were significantly different at the 5% level as determined by Duncan’s multiple range test (DMRT). Table 4. The interaction effects of spacing and organic fertilizer on lettuce traits. Spacing

Fertilizer

25×40 25×40 30×40 30×40 35×40 35×40 40×40 40×40

Humic acid Vitamint Humic acid Vitamint Humic acid Vitamint Humic acid Vitamint

Head diameter (cm) 11.41 bc 10.25 c 11.95 abc 14.31 a 12.92 ab 10.15 c 11.46 abc 11.43 bc

Number of leaf

NO3 (%)

25 d 31.5 ab 32 ab 33.3 a 29.5 abc 32.5 ab 28.6 bcd 26.5 cd

2.61 bcd 2.52 cd 2.62 bcd 2.9 b 2.62 bcd 3.22 a 2.75 bc 2.42 d

For the same variable, means with different letters were significantly different at the 5% level as determined by Duncan’s multiple range test (DMRT).

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Intl J Agri Crop Sci. Vol., 6 (16), 1137-1143, 2013 Table 5. The interaction effects of spacing and mulching on lettuce traits. Spacing 25×40 25×40 30×40 30×40 35×40 35×40 40×40 40×40

Mulch No mulch Mulch No mulch Mulch No mulch Mulch No mulch Mulch

P (%) 4.84 c 5.24 b 5.19 b 5.49 ab 5.68 a 5.23 b 5.41 ab 5.19 b

K (gr) 0.55 bc 0.54 c 0.59 a 0.58 ab 0.54 c 0.58 ab 0.55 bc 0.57 ab

For the same variable, means with different letters were significantly different at the 5% level as determined by Duncan’s multiple range test (DMRT). Table 6. The interaction effects of organic fertilizer and mulching on lettuce traits. Fertilizer

Mulch

Humic acid Humic acid Vitamint Vitamint

No Mulch Mulch No Mulch Mulch

Head diameter (cm) 11.98 a 12.39 a 10.2 b 12.87 a

NO3 (%)

K (%)

2.61 b 2.7 ab 2.85 a 2.68 ab

0.57 b 0.6 a 0.55 bc 0.54 c

For the same variable, means with different letters were significantly different at the 5% level as determined by Duncan’s multiple range test (DMRT). Table 7. The interaction effects of spcing, organic fertilizer and mulching on NO3 content of lettuce. Spacing 25×40 25×40 25×40 25×40 30×40 30×40 30×40 30×40 35×40 35×40 35×40 35×40 40×40 40×40 40×40 40×40

Fertilizer Humic acid Humic acid Vitamint Vitamint Humic acid Humic acid Vitamint Vitamint Humic acid Humic acid Vitamint Vitamint Humic acid Humic acid Vitamint Vitamint

Mulch No Mulch Mulch No Mulch Mulch No Mulch Mulch No Mulch Mulch No Mulch Mulch No Mulch Mulch No Mulch Mulch No Mulch Mulch

NO3(%) 2.62 bcdef 2.61 bcdef 2.57 cdef 2.47 ef 2.81 bcde 2.42 ef 2.8 bcde 3.01 b 2.3 f 2.95 bc 3.51 a 2.94 bcd 2.69 bcdef 2.8 bcde 2.53 def 2.31 f

For the same variable, means with different letters were significantly different at the 5% level as determined by Duncan’s multiple range test (DMRT).

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