Effect of Reducing Application of Chemical Fertilizers and Chemical Pesticides on Physiological Traits, Yield and Quality of Radish

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1. Institute of Economic Crops, Hubei Academy of Agricultural Sciences, Wuhan 430064, China; 2. Hubei Vegetable Office, Wuhan 430070, China; 3. Biological Pesticide Engineering Research Center, Hubei Academy of Agricultural Sciences, Wuhan 430070, China

1 Introduction

Radish is the second largest vegetable crop in Hubei Province. In 2015, the planting area of radish was 1.9 million mu, the annual output was about 4.4 million t, and the annual output value was about 5 billion yuan. Radish industry has developed into one of the pillar agricultural industries in the province, and one of the main sources of income of farmers. In the current situation of frequent outbreak of agricultural pests, chemical fertilizers and pesticides are excessively used in the process of radish cultivation, resulting in soil compaction, acidification, pesticide residue, increased insecticide resistance, environmental pollution, ecological balance damage and other problems, thereby posing a serious threat to radish quality and safety and environmental safety in the vegetable production areas. In order to ensure sustainable development of radish industry, we relied on Zhongxiang Jingsha Vegetable Cooperative to carry out test about reduction of chemical fertilizers and pesticides in Shayang main radish producing area during the spring of 2016. The purpose of this paper is to improve radish quality and production efficiency without affecting radish fleshy root yield by reducing application of chemical fertilizer, increasing application of functional organic fertilizer and trace elements, and fully using biological pesticides throughout the process of radish growth.

2 Materials and methods

2.1TestsoilThe test soil is sandy loam, and the physical and chemical properties are as follows: soil pH (5.8); organic carbon (8.3 g kg-1); total nitrogen (1.18 g kg-1); available phosphorus (9.7 mg kg-1); available potassium (98 mg kg-1); cation exchange capacity (CEC) (9.1 cmol kg-1).

2.2TreatmentsThe experiment had three treatments: N1(traditional fertilizer+ traditional chemical pesticides); N2(functional organic fertilizer+ trace elements+ traditional chemical pesticides); N3(functional organic fertilizer+ trace elements+ biological pesticides). The experiment was carried out in the core demonstration base of Zhongxiang Jingsha Vegetable Cooperative, and the plot area was 160 m2, repeated three times. The application rate of traditional fertilizer was as follows: compound fertilizer (60 kg/667 m2); N∶P∶K (15∶15∶15); organic fertilizer (40 kg/667 m2); calcium, magnesium, phosphate fertilizer (80 kg/667 m2). All fertilizers were from Yunnan Jinda Phosphorus Chemical Industry Co., Ltd. Functional organic fertilizers were the plant growth regulators and trace elements by adding pest-resistant and disease-resistant functional microbes and P, K-solubilizing functional microbes on the basis of traditional organic fertilizer to promote root growth. N, P, K total nutrient content>5%, and all fertilizers were used as basal fertilizers, produced by Bio-pesticide Center of Hubei Academy of Agricultural Sciences. The biological pesticides used during the growth of radish were matrine, Bt wettable powders, and Yelukang. It was sown on February 23, 2016, and harvested on May 7, 2016. Before harvesting, the fresh weight, moisture, soluble sugar, crude fiber, vitamin C, nitrate and pesticide residue in radish leaves and fleshy roots were measured, and the radish fleshy root yield was also measured. Moisture was measured using the general drying method; soluble sugar is measured using iodometry; crude fiber was measured using crude fiber determination method (GB/T 5009.10-2003); vitamin C was measured using 2, 6-chlorine indophenol titration; glucosinolates were measured using high performance liquid chromatography (NY/T 1103.3-2006); nitrate was measured using GB/T 5009.33-2010 method; organic phosphorus was measured using NY/T 761-2008 method.

2.3DataanalysisDPS data processing software was used for analysis of variance on data, and LSD method was used for multiple comparisons.

3 Results and analysis

3.1EffectofreducingapplicationofchemicalfertilizersandchemicalpesticidesonbiologicalcharacteristicsandyieldofradishTable 1 showed the effect of reducing application of chemical fertilizers and chemical pesticides on radish biological characteristics and fleshy root yield. There were no significant differences in radish plant height, spread, leaf length, leaf width and root length among treatments N1, N2and N3, while there were significant differences in radish root diameter, single root weight and yield among treatments N1, N2and N3. The yield under N2and N3was 4 673 kg/666.7 m2and 4 703 kg/666.7 m2, respectively, significantly higher than the yield under N1(4 595 kg/666.7 m2), indicating that increasing application of functional organic fertilizers and trace elements was favorable for the growth of the fleshy roots in the later growing stage of radish, possibly because traditional chemical fertilizers were generally quick-acting fertilizers, while functional organic fertilizers could provide long-term comprehensive nutrition for radish plants, increase and update soil organic matter, promote soil microbial reproduction, improve soil microenvironment, and increase radish fleshy root yield by adding the functional microbes and trace elements beneficial to the growth of radish.

Table1Effectofreducingapplicationofchemicalfertilizersandchemicalpesticidesonbiologicalcharacteristicsandyieldofradish

TreatmentPlantheightcmSpreadcmLeaflengthcmLeafwidthcmRootlengthcmRootdiametercmSinglerootweightkgRootyieldkg/666.7m2N142.5a59.6a36.4a18.5a28.1a8.03a0.74b4595bN241.9a60.1a35.9a18.4a27.5a8.68a0.83a4673aN342.7a57.7a36.0a18.6a29.6a8.71a0.85a4703a

Note: Different lowercase letters indicate significant difference (P=0.05), the same below.

3.2EffectofreducingapplicationofchemicalfertilizersandchemicalpesticidesonmainqualityindicatorsofradishAs can be seen from Table 2, reducing application of chemical fertilizers and chemical pesticides, increasing application of functional organic fertilizers, and spraying biological pesticides, could help to significantly improve the quality of radish. Compared with N1, after application of functional organic fertilizers and trace elements, the content of soluble sugar and vitamin C in fleshy root during the harvest of radish under N2and N3increased by 33.3 % and 6.06%, 33.3% and 7.58%, respectively; the content of crude fiber and nitrate under N2and N3decreased by 8.57% and 14.36%, 8.57% and 13.28%, respectively. There were no significant differences in glucosinolates and moisture content among treatments. There might be two reasons for the role of applying functional organic fertilizers and trace elements in reducing nitrate in radish fleshy root. Firstly, compared with chemical fertilizer, nitrogen forms are different. Functional organic fertilizer was slow-acting nitrogen fertilizer, and the nitrogen source was mainly organic nitrogen. After being applied into the soil, only after it was decomposed into available nutrient via the microbes could it be absorbed and used by radish. There was a small amount of nitrate nitrogen to be absorbed by radish, and after application, it could obviously reduce radish nitrate content. Pesticide residue refers to the pesticides that may remain on or in food after they are applied to food crops. In this experiment, chlorpyrifos were used during the radish seedling and fleshy root enlargement period. The results in Table 2 showed that N1, N2and N3had no significant effect on the content of chlorpyrifos in organophosphorus pesticides for radish, indicating that under traditional treatment and the treatment of reducing application of chemical fertilizers and chemical pesticides, there were no pesticide residues in radish products.

Table2Effectofreducingapplicationofchemicalfertilizersandchemicalpesticidesonmainqualityindicatorsofradish

TreatmentSolublesugar%VitaminCmg/100gCrudefiber%Moisturecontent%Glucosinolatesumol/gNitratemg/kgChlorpyrifosinorganophosphoruspesticides∥mg/kgN10.03b13.2b3.8a94.6a24.17a92.6a0aN20.04a14.0a3.5b94.5a22.10a79.3b0aN30.04a14.2a3.5b94.4a21.93a80.3b0a

4 Conclusions and discussions

Excessive application of chemical fertilizers and chemical pesticides is the main reason for the low utilization efficiency of fertilizers and the deterioration of soil environment in China, resulting in a huge waste of resources and affecting the sustainable development of agriculture[1-2]. Reducing chemical fertilizer input, increasing application organic fertilizer and functional microbes, and efficiently managing nutrient resources according to the crop fertilizer requirement[3-5], is the fundamental way to achieve high crop yield, efficient use of resources and farmland environmental protection, and the inevitable choice to promote sustainable agricultural development[6]. The results showed that reducing the input of chemical fertilizers, and increasing application of organic fertilizers and functional microorganisms, could provide a variety of inorganic and organic nutrients, and pro-duce lasting and stable fertilizer effect, with the advantages that chemical fertilizers can not replace, thereby significantly improving radish yield and radish quality. Applying functional organic fertilizer and trace elements could help to significantly improve radish fleshy root yield, increase soluble sugar and vitamin C content, and reduce the content crude fiber, nitrate and chlorpyrifos in organophosphorus pesticides, but there was no significant effect on the content of glucosinolates in radish. Due to the promotion and restriction, growth and decline mechanism, different functional organic fertilizers and trace elements affected radish yield and quality by a series of physiological and metabolic activities, so there was a need to conduct systematic research on the numerical relationship and regulatory mechanism between them, so as to provide technical support for high yield, high quality and high efficiency of radish.

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