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Agricultural College, Yanbian University, Yanji 133002, China

1 Introduction

Due to excessive use of inorganic fertilizer and chemical pesticide and long-term continuous cropping, many problems are emerging, including the decline of soil fertility and microbial diversity, accumulation of auto toxin and soil borne disease, soil acidification[1-2]. Finally, it could make crop yield and quality decline, and environment be contaminated. In recent years, organic fertilizer improving plant nutrition is paid much attention to. Organic fertilizer could improve microecological structure and physical-chemical property of soil and directly increase organic matter content in soil[3-5]. In tomato pot experiment, it could improve physical properties and fertility of soil, increase the number of beneficial bacteria and tomato yield by taking cottonseed shell as organic fertilizer[6-7]. In the research of Lu Lilanetal., the fertilization amount of 75% organic fertilizer+25% chemical fertilizer could make plant height, stem diameter and leaf area of patchouli respectively increase by 47.06%, 123.64% and 94.64%[8]. Li Pingpingetal. studied the effects of different organic fertilizer treatments on yield and quality of spring tea and soil nutrient content, and results showed that the treatment of 70% organic fertilizer+30% chemical fertilizer had the most significant impact, and average yield increased by 276.91% than control[9].

The source of organic fertilizer is wide, such as agricultural waste, animal faeces, crop residue and compost[10]. The compost fermented by solid organic waste is applied in agricultural cultivation, which becomes research hot spot in organic agriculture in recent years. The compost could improve crop yield and quality, reduce crop disease incidence, improve physical-chemical properties of soil and increase microbial diversity in soil[11-13]. Mixed application of organic manure and inorganic fertilizer in production must select suitable proportion, which could decline nitrate content in fruit and make vegetable quality and yield be greatly improved[14].

To effectively use solid organic waste and improve spinach yield and quality, by singly adding organic fertilizer and mixing organic fertilizer and chemical fertilizer, fertilizer proportion suitable for spinach growth was studied via root length, plant height, leaf nitrogen content, nitrogen content, fresh weight and dry weight, which could provide theoretical basis for actual agricultural production.

2 Materialsandmethods

2.1ExperimentalmaterialsBiological organic fertilizer was provided by Agricultural College of Yanbian University, spinach seed was produced by Yanbian Sanlin Seed Industry, and chemical fertilizer was commercially available.

2.2TestsoilThe soil from test site of Agricultural College of Yanbian University (soil type in the region was mainly gray brown soil) was sieved, and stone was removed.

2.3ExperimentaldesignThere were ten formulas in the test, specific formulas of A, B, C, D, E, F, G, H, I and J were shown as Table 1. The test designed two treatments: single organic fertilizer and organic fertilizer+chemical fertilizer, and CK was control. In organic fertilizer treatment, pot test was conducted according to 1%, 5% and 10% of soil weight, and added amount of chemical fertilizer was fixed: 0.74 g N, 0.65 g P and 0.18 g K (Table 2). Each treatment had two repeats, and design in random district was conducted. Ten plants of spinach were planted in each pot, with 2 cm of soil cover, 400 mL of water was given in time, and other treatments were same. Three plants of spinach with the best growth were selected from each pot to measure leaf chlorophyll content (chlorophyll meter: Meinengda SPAD-502Plus), nitrogen content (plant nutrient tacheometer: Zhejiang Putuo Instrument Co., Ltd. TYS-3N), leaf temperature, leaf width, plant height, root length and fresh weight.

3 Resultsandanalyses

3.1TheimpactonchlorophyllcontentofspinachleavesbydifferentfertilizationtreatmentsOrganic fertilizer could significantly improve chlorophyll content of spinach leaves. As shown in Fig.1, chlorophyll content in the treatment of only adding organic fertilizer was all higher than that in CK1. Moreover, chlorophyll content in the combination of organic fertilizer + chemical fertilizer was higher than that in the treatment of only adding organic fertilizer except A1-A2, B3-B4, F3-F4and F5-F6. It illustrated that chlorophyll content of spinach leaves was higher in B2, B6, D4, D6, E4and G2, showing that the several treatments could promote the synthesis of spinach chlorophyll.

Table1Originalproportionofcompost

DifferenttreatmentsSoybeanmeal∥kgChinesetraditionalmedicineresidue∥kgWoodvinegar∥LBacterialfluid∥LA4．54．52．120B4．59．02．120C4．518．02．120D9．04．52．120E9．09．02．120F9．018．02．120G18．04．52．120H18．09．02．120I18．018．02．120J9．018．02．123．37

Table2Potexperiment

TreatmentOrganicfertilizer∥gChemicalfertilizerSoil∥kgTreatmentOrganicfertilizer∥gChemicalfertilizerSoil∥kgA1181．8F1181．8A218+1．8F218+1．8A3901．8F3901．8A490+1．8F490+1．8A51801．8F51801．8A6180+1．8F6180+1．8B1181．8G1181．8B218+1．8G218+1．8B3901．8G3901．8B490+1．8G490+1．8B51801．8G51801．8B6180+1．8G6180+1．8C1181．8H1181．8C218+1．8H218+1．8C3901．8H3901．8C490+1．8H490+1．8C51801．8H51801．8C6180+1．8H6180+1．8D1181．8I1181．8D218+1．8I218+1．8D3901．8I3901．8D490+1．8I490+1．8D51801．8I51801．8D6180+1．8I6180+1．8E1181．8J1181．8E218+1．8J218+1．8E3901．8J3901．8E490+1．8J490+1．8E51801．8J51801．8E6180+1．8J6180+1．8

3.2TheimpactonnitrogencontentofspinachleavesbydifferentfertilizationtreatmentsOrganic fertilizer could significantly improve nitrogen content of spinach leaves. As shown in Fig.2, nitrogen content in the treatment of only adding organic fertilizer was higher than that in CK1. Moreover, nitrogen content in the treatment of organic fertilizer + chemical fertilizer was higher than that in the treatment of only adding organic fertilizer except A1-A2, C1-C2, F5-F6and I3-I4. It illustrated that nitrogen content was higher in B6, C1, D4, G2, H2, H4and I3, showing that the several treatments could promote nitrogen synthesis of spinach leaves.

Fig.1Theimpactonchlorophyllcontentofspinachleavesbydifferentfertilizationtreatments

Fig.2Theimpactonnitrogencontentofspinachleavesbydifferentfertilizationtreatments

3.3TheimpactonleaftemperatureofspinachbydifferentfertilizationtreatmentsAs shown in Fig.3, leaf temperature in all treatments was all higher than CK1, and leaf temperature in the treatment of organic fertilizer+chemical fertilizer was all higher than that in the treatment of only adding organic fertilizer. Lower leaf temperature was induced by evaporation. The lower the temperature, the more intense the evaporation. Evaporation could assist nutrient transportation and adjust the temperature in plant body. Too high temperature could burn leaf and affect enzyme activity, thereby affecting a series of physiological responses in the plant body. Evaporation also could discharge part of the harmful substance, which was more favorable for plant adapting to environment. Therefore, the treatment of only adding organic fertilizer was more suitable for spinach growth.

Fig.3Theimpactonleaftemperatureofspinachbydifferentfertilizationtreatments

3.4TheimpactonleafwidthofspinachbydifferentfertilizationtreatmentsOrganic fertilizer could promote leaf width of spinach to a certain degree. As shown in Fig.4, leaf width in the treatment of only adding organic fertilizer was wider than CK1, and leaf width in the treatment of organic fertilizer + chemical fertilizer except C1-C2, D1-D2, F1-F2, and J1-J2was all lower than that in the treatment of only adding organic fertilizer. It illustrated that chemical fertilizer caused excess of one element, thereby inhibiting leaf width. Among them, leaf width in A3, A5, E5, F3, I3, I5and J3was the maximum, showing that the several treatments could obviously promote spinach leaf growth.

3.5TheimpactonplantheightofspinachbydifferentfertilizationtreatmentsAs shown in Fig.5, plant height in the treatment of only adding organic fertilizer was generally higher than that in the treatment of organic fertilizer + chemical fertilizer. Plant height in the treatment of only adding organic fertilizer was basically higher than CK1except G and H, in which the growth was the best in A5, B5, C5, E5, F3, I5, J3and J5. In summary, organic fertilizer could promote plant height of spinach, but the addition of chemical fertilizer inhibited plant growth. It illustrated that organic fertilizer could provide the best nutrient proportion for the plant, and the addition of chemical fertilizer caused overnutrition, with counteraction. Especially plants in G and H could not grow, illustrating that G and H were not suitable for spinach production.

Fig.4Theimpactonleafwidthofspinachbydifferentfertilizationtreatments

Fig.5Theimpactonplantheightofspinachbydifferentfertilizationtreatments

3.6TheimpactonrootlengthofspinachbydifferentfertilizationtreatmentsAs shown in Fig.6, root length in the treatment of only adding organic fertilizer was generally higher than that in the treatment of organic fertilizer + chemical fertilizer, in which root length was the longest in A3, A5, C5, C6, E5, F3, J1, J5and J6, showing that organic fertilizer could significantly promote the growth of spinach root under these concentration formulas.

Fig.6Theimpactonrootlengthofspinachbydifferentfertilizationtreatments

3.7TheimpactonfreshweightofspinachbydifferentfertilizationtreatmentsSeen from Fig.7, fresh weight in the treatment of only adding organic fertilizer was generally higher than that in the treatment of organic fertilizer + chemical fertilizer, and fresh weight in the treatment of only adding organic fertilizer except G and H was all higher than CK1. Among them, fresh weight was the maximum in A5, C3, E5, F3, I5and J5, illustrating organic fertilizer could promote spinach yield increase, but the addition of chemical fertilizer may cause excess of some elements, thereby inhibiting spinach growth. G and H were not suitable for spinach growth, which could be excluded.

Fig.7Theimpactonfreshweightofspinachbydifferentfertilizationtreatments

4 Conclusions

Via comprehensive analysis, the most suitable organic fertilizer proportion of spinach was found, and they were A5: soybean meal 4.5 kg, Chinese traditional medicine residue 4.5 kg; E5: soybean meal 9 kg, Chinese traditional medicine residue 9 kg; I5: soybean meal 18 kg, Chinese traditional medicine residue18 kg; F3: soybean meal 9 kg, Chinese traditional medicine residue 18 kg. Under the situation that other conditions were same, the most suitable proportion of soybean meal and Chinese traditional medicine residue for spinach growth was about 1∶ 1.

Via contrast test of organic fertilizer and chemical fertilizer, it was found that organic fertilizer could promote spinach growth and yield increase, but the addition of chemical fertilizer may cause one element excess in soil, thereby inhibiting spinach growth, which needed deep research and exploration.

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