Effects of Raising Chickens Under Moringa oleifera

Liping PAN Hanyu ZHU Ying XING Guoxin SHA Jinping CHEN Yongxian LIU

Forests on Soil Nutrients and Selenium Absorption by  M. oleifera

Abstract ［Objectives］ This study was conducted to investigate the effects of raising chickens under  Moringa oleifera  forests on soil nutrient changes and selenium absorption by  M. oleifera .

［Methods］The nutrient contents of the soil and the selenium contents of different parts of  M. oleifera  were determined and analyzed.

［Results］ Raising chickens under the investigated  M. oleifera  forest improved the soil. Compared with the control, the soil organic matter, hydrolyzable nitrogen, available phosphorus, and available potassium of the plots for underforest chicken raising were significantly improved; the changes were the most significant within the range of 2 m from the chicken houses, respectively, and the values were 1.39, 1.38, 1.52 and 1.31 times of the control, respectively; soil bulk density decreased, total porosity increased, soil structure and permeability improved, and soil pH values at 2 and 5 m away from the chicken houses were significantly higher than the control by 0.34 and 0.28 unit, respectively; and raising chickens under the forest promoted the absorption and utilization of selenium in  M. oleifera , and the selenium contents in stems and leaves of  M. oleifera  were 1.64 times and 1.51 times of the control, respectively.

［Conclusions］This study provides a theoretical basis for the high-value selenium-enriching compound economic model of raising chickens under  M. oleifera  forests.

Key words  Moringa oleifera ; Raising chickens under forests; Soil nutrients; Selenium

Received: June 28, 2021  Accepted: August 29, 2021

Supported by Science and Technology Research and Technology Development Plan of Xixiangtang District, Nanning City (2019021702); Special Project of the Science and Technology Vanguard Special Action of Guangxi Academy of Agricultural Sciences (GNKM 202114); Guangxi Selenium-rich Featured Crops Experimental Station (GTS2016011); Team Project of Guangxi Academy of Agricultural Sciences (GNK 2020YT039); Nanning Science and Technology Research and Technology Development Key R&D Program Project (20202087, 20212020).

Liping PAN (1988-), female, P. R. China, assistant research fellow, devoted to research about soil ecology and high-value agriculture.

*Corresponding author. E-mail: liuyx27@163.com.

Underforest economy engages in three-dimensional compound production and management such as underforest planting and breeding while making full use of the advantages of underforest land resources and shade, with the help of the ecological environment of the forest land, so as to realize the ecological agriculture model of complementary resource advantages and coordinated development［1］. Studies have shown that chicken manure from ecological chicken farming under forests can improve soil properties［2］ and provide nutrients for plants［3］ as organic fertilizer; and meanwhile, there are a large number of weeds, young leaves and insects in forest land, which can reduce feed costs, and the chickens raised are ecological and have delicious meat quality and good economic benefits［4-5］.

M. oleifera  is a kind of tropical plant with unique economic value. Its nutritional value and medicinal value have been widely confirmed, and enjoys the reputation of "Tree of Life", "Miracle Tree", and "Vegetarian Gold". It is a plant that perfectly combines edible, health care and ornamental value.  M. oleifera  leaves are rich in crude protein, mineral elements, vitamins and amino acids,  etc. , and their higher biomass, better palatability and digestibility provide a basis for the feeding value of  M. oleifera  leaves［6］. Selenium is an indispensable and important element in the human body and has made a significant contribution to maintaining human health. For example, it can resist oxidation and delay cell senescence; and it can reduce the incidence of cancer and other diseases, and especially, can effectively prevent prostate cancer［7］. It has been found that the roots, stems and leaves of  M. oleifera  have high selenium content. The selenium enrichment effect of  M. oleifera  is significantly higher than that of other agricultural products. As a high value-added multifunctional plant,  M. oleifera  can be used for diversified development and comprehensive utilization［8-9］. In recent years, more and more attention has been paid to the research of  M. oleifera . However, as an emerging industry, its research in Guangxi started late and is still in its infancy. Therefore, the development of underforest economy is an important way to improve the land utilization rate and economic benefits of  M. oleifera . At present, there are few reports on the effects of breeding under  M. oleifera  forests on the utilization of selenium in  M. oleifera . The purpose of this study was to investigate the effects of raising chickens under  M. oleifera  forests on forest soil nutrient content and Moringa selenium accumulation, and analyze its improvement effects on the soil nutrients of  M. oleifera  forests and its effect on  M. oleifera  selenium accumulation, hoping to provide a theoretical basis for the high-value selenium-enriching compound economic model of raising chickens under  M. oleifera  forests.

Materials and Methods

General situation of experimental fields

The test site was located in the beautiful southern  M. oleifera  production base in Nanning, Guangxi. The test area was a 4-year-old  M. oleifera  plantation, and the row spacing of  M. oleifera  was 1 m×1 m. The total selenium content of the soil was 0.92 mg/kg.

Plot setting and stocking density

From late October 2020 to early January 2021, three-yellow chickens will be stocked under the  M. oleifera  plantation. The stocking area was 15 m×10 m, separated by wire fences, and 250 three-yellow chickens of 90 days old were continuously stocked. With chicken houses as the center, sample plots were set at 2, 5, and 10 m way from the chicken houses in the  M. oleifera  plantation, numbered R2, R5, R10, and the  M. oleifera  land outside the fence without chickens was set as a control, designate as R0.

Collection of soil samples

After all the chickens in the test site were released, the five-point sampling method was adopted for sampling within the range of each plot. Specifically, five points were randomly selected, and an equal amount of mixed samples of the 0-20 cm soil layer in the area were collected with a cutting ring, and bagged, sealed, and quickly brought to the laboratory for related processing. When taking soil samples,  M. oleifera  stalks and leaves of the same height were collected in the sample plots 5 m away from the chicken houses and the control area, and they were brought back to the laboratory, dried at 65 ℃, and crushed for later use.

Determination of soil and plant nutrient contents

For the soil samples, the soil bulk density was determined by the weighing method; the total porosity was determined by the water immersion method; the pH value was determined by the water immersion-acidity meter method; the organic matter content was determined by the potassium dichromate oxidation-external heating method; the hydrolyzable nitrogen content was determined by the alkaline hydrolysis diffusion absorption method; the determination of available phosphorus content adopted the sodium hypochlorite extraction-molybdenum antimony colorimetric method; and the ammonium acetate extraction-flame photometric method was used for determination of available potassium content.  M. oleifera  samples were determined by hydride generation-atomic fluorescence spectrometry for selenium content, flame atomic absorption spectrometry for cadmium content, and Folin-phenol method for protein content.

Data processing and analysis

Excel2007 and SPSS19.0 data processing system were used for statistics and analysis.

Results and Analysis

Effects of raising chickens under the  M. oleifera  plantation on soil nutrient changes

Soil is the material basis for vegetation to survive, and good soil physical properties are an important sign of fertile soil, which plays an important role in the growth and development of plants［10］. Soil nutrients play an important role in soil fertility. It can be seen from Table 1 that raising chickens under forests had varying degrees of effects on the changes of soil nutrients, and the effects showed a decreasing trend with the distance from chicken houses increasing. Compared with the control, the soil organic matter, hydrolyzable nitrogen, available phosphorus, and available potassium of the underforest chicken plots were significantly improved. The changes were the most significant within the range of 2 m from the chicken houses, and the values were 1.39, 1.38, 1.52 and 1.31 times of the control. Bulk density and total porosity of the soil can reflect the structure and permeability of the soil. The measurement results in Table 1 showed that the bulk density of the soil for raising chickens decreased and the total porosity increased, and the soil bulk density and total porosity also changed most significantly at a distance of 2 m from the chicken houses. The change trend of soil pH was consistent with the change trends of nutrients. Raising chickens under the forest could increase soil pH. Specifically, the pH values of the soil 2 and 5 m away from the chicken houses were significantly higher than that of the control, while the pH of the soil far away from the chicken houses had no obvious differences from the control.

Effects of raising chickens under forest on the accumulation of selenium and proteins in  M. oleifera

It can be seen from Table 2 that raising chickens under the  M. oleifera  forest had a certain effect on the growth of  M. oleifera , and promoted the accumulation of proteins in  M. oleifera . The protein contents of both stems and leaves were significantly higher than those of the control ( P <0.05), respectively, increased by 18.4% and 5.6% compared with the control, respectively. Similar to the change of proteins, the absorption and utilization of selenium by  M. oleifera  was improved. The selenium contents in the stems and leaves of  M. oleifera  were 1.64 and 1.51 times of the control, respectively. It could be seen that raising chickens under the forest improved the soil properties of  M. oleifera  woodland, promoted  M. oleifera  growth, improved  M. oleifera ‘s absorption and utilization of selenium in the soil, increased protein content, and improved quality.

Conclusions and Discussion

In this study, a plantation of Guangxi characteristic crop  M. oleifera  was selected as the experimental site for underforest chicken raising to explore the effects of underforest chicken raising on forest soil physical properties, soil nutrient contents and plant nutrient contents. It was found that compared with the control, the soil organic matter, hydrolyzable nitrogen, available phosphorus, and available potassium of the plots for underforest chicken raising significantly increased, and the most significant changes were within the range of 2 m from the chicken houses,. Specifically, the organic matter increased by 9.3 g/kg, the hydrolyzable nitrogen increased by 36.96 mg/kg, the available phosphorus increased by 14.53 mg/kg, the available potassium increased by 55.00 mg/kg, and with the increase of the distance from the chicken houses, the effects showed a downward trend, which is consistent with the research conclusions of Lin  et al. ［12］. It was because chickens moved more frequently near the chicken houses, leaving a lot of chicken manure as a green organic fertilizer, which contained a lot of nutrients such as nitrogen, phosphorus, and potassium, and could enhance the nutrient contents of the soil, optimize the structural composition of the soil microbial community, improve soil biological and biochemical characteristics［11］, increase the availability of soil nutrients, and significantly improve soil nutrients. The results of Zeng  et al. ［13］ showed that raising chickens under forests made the soil bulk density smaller and the total porosity increase, so the soil became looser and had good water retention property and air permeability. In this study, the bulk density of the soil for underforest chicken raising became smaller and the total porosity increased. Also, the soil bulk density and total porosity at a distance of 2 m from the chicken houses changed most significantly. It was because the soil for raising chickens under the forest increased the organic matter content of the soil due to the increase of chicken manure, which made the soil surface looser, the soil porosity increase, and the physical and chemical properties of the soil improved, which was conducive to the growth of  M. oleifera . The mode of raising chickens under  M. oleifera  forests can make full use of the land resources under forests, reduce the input of chemical fertilizers, reduce the cost of forest farmers, and improve the overall economic benefits of forest land.

Guangxi has a vast selenium-rich soil, but the soil is generally acidic, and the activity of selenium in acidic soil is low. From the results of this study, it was found that the pH of the soil closer to the chicken houses was significantly higher than that of the control, while the pH of the soil farther from the chicken houses was not significantly different from the control. It can be concluded that the mode of raising chickens under  M. oleifera  forests can not only increase the pH of the forest land, activate the selenium in the soil, and increase the absorption and utilization of selenium in the soil by  M. oleifera , thereby increasing the selenium content in the stems and leaves of  M. oleifera , promoting the growth of  M. oleifera  to a certain degree, and increasing the protein content of  M. oleifera , which is beneficial to improve the quality of  M. oleifera  and increase the feeding value of  M. oleifera . There are many reports on the relationship between selenium content and protein content. Yin  et al. ［14］ found that the higher the protein content of plant foods, the higher the selenium content, and there was a very significant positive correlation between the two. Raising chickens under  M. oleifera  forests is a new model combining forests and livestock, which makes full use of the unique selenium-rich soil in the Zhuang nationality mountain area of Guangxi to produce original ecological food, thereby improving the economic benefits of farmers and having broad development prospects. However, if it is not handled properly, raising chickens under forests will destroy forest biodiversity and other issues to a certain extent. The results of this study indicate that raising chickens under  M. oleifera  forests can increase the selenium content in  M. oleifera  stems and leaves, and has a certain promoting effect on the growth of  M. oleifera . Therefore, in order to achieve sustainable and circular green ecological underforest farming, the next step is to explore the effects of soil nutrients and structural changes on the growth of  M. oleifera  trees, as well as the best feeding density or best feeding methods, so as to achieve synchronize development of economic benefits and ecological benefits.

Raising chickens under  M. oleifera  forests could improve the physical and chemical properties of the soil, increase the contents of nitrogen, phosphorus, and potassium in the soil, increase soil nutrients, and activate the selenium in the soil. The contents of proteins and selenium in the plant also increased, which promoted the growth of  M. oleifera , promoted the absorption and utilization of selenium in the soil by  M. oleifera , and improved the quality of  M. oleifera .

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