Response of corn yield to water retaining agents, inhibitors, and corn stalks addition in semi-arid cropland

Wu, K., Lv, N., Bai, W., Meng, Y., Han, M., Xue, Y., Song, Y., Xie, X., Wang, T., Gong, P., and Zhang, L. (2024). “Response of corn yield to water retaining agents, inhibitors, and corn stalks addition in semi-arid cropland,” BioResources 19(2), 3637-3652.

Abstract

Drought, excessive use of nitrogen fertilizer, and decline in soil organic matter threaten corn production. This study investigated the potential of water retaining agents, inhibitors, and corn stalks in enhancing soil physicochemical properties to bolster corn yield in semi-arid farmlands. In our study, polyacrylamide addition increased the content of ammonium nitrogen (NH₄⁺-N) and nitrate nitrogen (NO₃^–-N) in the seedling stage, exchangeable potassium (K) in the mature stage but decreased the content of available phosphorus (P) in the seedling stage. Potassium polyacrylate addition increased the content of NH₄⁺-N and decreased the content of available P in the seedling stage. The addition of inhibitors decreased the content of NH₄⁺-N and available P in the seedling stage, NO₃^–-N and available P in the jointing stage, and NH₄⁺-N in the mature stage, respectively. Corn stalks returning could maintain soil moisture, decrease the content of NH₄⁺-N in the seedling stage and exchangeable K in the mature stage, and increase the content of available P and exchangeable K in the seedling stage. Combined application of inhibitors and corn stalks could increase soil organic carbon (SOC) and ensure corn yield, which was the best fertilization mode in semi-arid cropland.

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Response of Corn Yield to Water Retaining Agents, Inhibitors, and Corn Stalks Addition in Semi-arid Cropland

Kaikuo Wu,^a Na Lv,^a,b Wei Bai,^c Yue Meng,^a,b Mei Han,^d Yan Xue,^a Yuchao Song,^a Xueshi Xie,^e Tingting Wang,^e Ping Gong,^a,* and Lili Zhang ^a,*

DOI: 10.15376/biores.19.2.3637-3652

Keywords: Polyacrylamide; Potassium polyacrylate; NBPT; DMPP; Corn stalks

Contact information: a: Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China; b: University of Chinese Academy of Sciences, Beijing 100049, China; c: Liaoning Key Laboratory of Conservation Tillage in Dry Land, Tillage and Cultivation Research Institute, Liaoning Academy of Agricultural Science, Shenyang 110161, China; d: Industrial Transformation and Revitalization Service Center of Fuxin, Fuxin 123000, China; e: Stanley Agriculture Group Co. Ltd., Linshu, Shandong, 276700, China; *Corresponding author: llzhang@iae.ac.cn; gongping@iae.ac.cn;

Kaikuo Wu and Na Lv contributed equally;

INTRODUCTION

Corn is one of the most important food crops in the world, providing at least 30% of food calories for 4.5 billion people in 94 developing countries worldwide (Tefera et al. 2016). China accounts for 21% of the world’s corn production (Xia et al. 2020). Liaoning Province is one of the 13 major grain-producing areas in China. The planting area of spring corn is more than 2 million hectares, of which the northwest area of Liaoning Province accounts for more than 2/3, and the output accounts for more than 75% of Liaoning Province. Therefore, corn production in the region is crucial for China’s food security (Zhe et al. 2020). However, this area belongs to semi-arid cropland with a record of water shortage, and long-term cultivation has led to the decline of soil organic matter, which restricts the production of corn (Meng et al. 2023; Rix et al. 2023). Therefore, measures need to be taken to alleviate the constraints of these factors on corn production.

Water retaining agents are substances that can be added to soil to alleviate crop loss caused by drought. Among these are polyacrylamide (PAM) and potassium polyacrylate (K-PAA), which are commonly used (Wu et al. 2018; Zhao et al. 2023). Moreover, water retaining agents have the characteristics of promoting plant growth and root secretion, increasing soil enzyme activity, etc., which may improve the transformation of nutrients in the soil and promote corn production (Zhang et al. 2020a). In addition to water limitation, nitrogen (N) is also one of the most critical elements affecting crop yield. However, excessive fertilization in production practices can lead to a serious imbalance between the available nutrients provided by soil and the actual needs of crops (Cui et al. 2022). To deal with this problem, urea inhibitors and nitrification inhibitors are added to fertilizers to regulate the transformation process of fertilizer N in soil (Scherer et al. 2014; Li et al. 2023). Urease inhibitors can delay urea hydrolysis by inhibiting urease activity. Nitrification inhibitors reduce the formation and accumulation of nitrate by inhibiting the conversion of ammonium (NH₄⁺) to nitrate (NO₃^–) (Liu et al. 2023). The combined application of urease inhibitors and nitrification inhibitors is considered to have better yield increasing effects (Qi et al. 2022). However, maintaining high crop yields in the long term also requires fertile soil. To alleviate soil degradation and improve soil fertility, measures of returning straw to the soil (i.e. “straw returning”) have emerged (Zheng et al. 2021; Meng et al. 2023). Straw contains a large amount of lignocellulose, soluble carbon, and other nutrient elements, and it has good porosity (Thíebeau et al. 2021; Lu et al. 2023). These characteristics of straw are often used to improve soil physicochemical properties, promote soil moisture and fertilizer retention, and ensure crop yield (Velthof et al. 2002; Wu et al. 2021). However, further clarification is needed regarding whether adding water retaining agents, inhibitors, and straw can promote corn production in this semi-arid cropland.

The cinnamon soil of western Liaoning was taken as the test object to explore the effects of water retaining agents, inhibitors, and corn stalks addition on corn yield, which provided scientific basis for rational utilization of corn stalks resources, promotion of high yield of corn and improvement of soil fertility.

EXPERIMENTAL

Field Site and Experimental Design

The field experiment was conducted at the field experimental station of the Liaoning Key Laboratory of Water-Saving Agriculture in Fuxin County, northeast China. The annual average temperature is 7.2 °C, the annual average precipitation is about 480 mm, and the average sunshine time is about 2865 h. The rainfall situation in 2021 is shown in Fig. 1. The test soil was cinnamon soil with an organic matter content of 13.4 g kg^-1, a total N of 1.0 g/kg, a total phosphate (P) of 0.4 g/kg, a total potassium (K) of 22.8 g/kg, an available P of 53.6 mg kg^-1, and an exchangeable K of 86.7 mg kg^-1. Soil bulk density (0 to 20 cm) was 1.51 g cm^-3, and the pH (H₂O) was 5.5. The field was set up in spring 2021. The farming system is continuous corn with one season per year. The split zone experiment design with three replicates was adopted, and the main division was divided into 3 treatments, which were natural rainfall (R), adding water retaining agent PAM (white small particle cationic polymer produced by Yunze Chemical Co., Ltd. for water retention), and adding water retaining agent potassium polyacrylate (K-PAA) (white small particle polyacrylate water retaining agent produced by Hairuida Co., Ltd). The subdivision was divided into 5 treatments, namely no fertilization control (CK), conventional fertilization (U), conventional fertilization + corn stalks (US), conventional fertilization + inhibitors (UI), and conventional fertilization + inhibitors + corn stalks (UIS). The dosage of PAM and K-PAA was 30 kg hm^-2. The conventional fertilizer used for fertilization were urea, superphosphate, and potassium chloride (KCl), and the application levels were N 156 kg ha^-1, P 26 kg ha^-1, and K 60 kg ha^-1, respectively. The inhibitors were NBPT (N-(n-butyl)thiophosphoric triamide) and DMPP (3,4-dimethylpyrazole phosphate), applied at a dosage of 1% and 2% of urea N, respectively. Corn stalks were crushed (5 to 10 cm) and returned to the field (9.0 tons ha^-1). All fertilizers were applied once during planting on May 10, 2021. The area of each plot was 40 m² (5 m × 8 m). The planting density of the corn was 55,000 plants ha^-1. The corn variety was “H188” spring maize (Zea mays L., a late maturing maize variety based on Food and Agriculture Organization of the United Nations (FAO) standards, with a 127 day growing period). Fertilizer was spread and rotary plowed to a depth of 15 to 20 cm before sowing. Plant protection and irrigation were not used. Weeds were pulled manually, and the corn was harvested manually.

Fig. 1. Rainfall during the 2021 corn growing season

Sample Collection and Analysis

Three soil cores were randomly selected from each treatment plow layer (0 to 20 cm) during the corn seedling stage (June 16^th), jointing stage (July 16^th), filling stage (August 18^th) and mature stage (September 24^th). The soil samples were composited, sieved (2 mm), and stored at 4 °C until used for analysis. Soil moisture content was determined using the aluminum box drying method (105 °C). Soil moisture content is the percentage of water in the soil as a percentage of the weight of fresh soil. Soil ammonium nitrogen (NH₄⁺-N) and nitrate nitrogen (NO₃^–-N) were extracted with 2 M KCl solution (Meng et al. 2023), filtered, and analyzed with a continuous flow analyzer (AA3, Bran + Luebbe, Norderstedt, Germany). Available P was extracted using 0.5 mol/L NaHCO₃, and available K was extracted using neutral 1 mol/L ammonium acetate (NH₄Oac) (Zhao et al. 2004). Soil organic carbon (SOC) and total N contents were determined by dry combustion of the samples using an Elemental Analyzer (Vario EL III, Hanau, Germany) (Yang et al. 2017). The corn yield was measured after air drying.

Statistical Analysis

All analyses were performed using Statistical Package for the Social Sciences (SPSS) Statistics 16.0 (SPSS Inc., Chicago, IL, USA). One-way analysis of variance (ANOVA) was used for testing the treatment effects with Duncan analysis. Significance was P < 0.05. Pearson correlation analysis was used for the correlation between corn yield and soil physicochemical properties. The response of corn yield to the application of water retaining agents, inhibitors, and corn stalks was analyzed using univariate analysis of variance. Tables and figures were prepared with Excel 2016 (Microsoft Corp., USA) and Origin 8 (Origin Lab Corp., USA), respectively. The data in the figures and tables are the average value ± standard error.

RESULTS AND DISCUSSION

Soil Moisture Content

The variation range of soil moisture content in different corn growth periods was 13% to 18% (Table 1). The mature stage had the highest soil moisture content (17% to 18%), followed by jointing stage (16% to 18%), filling stage (15% to 16%), and seedling stage (13% to 17%). The treatments with the highest soil moisture content during the corn seedling stage were AUIS (17%), BUIS (17%), AUS (16%), RUS (16%), BUS (16%), and RUIS (16%), while the lowest treatment was RU (13%). There was no significant difference in soil moisture content among all treatments in other periods. Corn stalks returning was able to significantly reduce soil moisture loss in corn seedling stage (Table S1).

Soil Ammonium Nitrogen

The content of NH₄⁺-N in soil was the highest at the corn seedling stage, and then it decreased rapidly. The content of NH₄⁺-N remained stable at the corn filling stage and maturity stage (Table 2). The addition of water retaining agents, inhibitors and corn stalks significantly affected the soil NH₄⁺-N content in corn seedling stage, among which the application of PAM increased the soil NH₄⁺-N content, and the addition of inhibitors and corn stalks decreased the soil NH₄⁺-N content (Table S2). The addition of water retaining agents and inhibitors also significantly affected the soil NH₄⁺-N content at corn mature stage, in which the application of K-PAA increased the soil NH₄⁺-N content, and the addition of inhibitors decreased the soil NH₄⁺-N content (Table S2).

Table 1. Soil Moisture Content in Topsoil at Different Growth Stages of Corn

Table 2. NH₄⁺-N (mg kg^-1) in Topsoil at Different Growth Stages of Corn

Soil Nitrate Nitrogen

The content of NO₃^–-N in soil was the highest at corn seedling stage, and then it decreased rapidly. The content of NO₃^–-N remained stable at corn mature stage (Table 3). The addition of water retaining agents significantly affected soil NO₃^–-N content at the seedling stage and jointing stage, and the addition of PAM significantly increased soil NO₃^–-N content. The application of inhibitors significantly reduced the soil NO₃^–-N content in the corn jointing stage (Table S3).

Table 3. NO₃^–-N (mg kg^-1) in Topsoil at Different Growth Stages of Corn.

Table 4. Available P (mg kg^-1) in Topsoil at Different Growth Stages of Corn

Soil Available Phosphorus

The content of available P in soil changed little in different growing periods of corn (Table 4). The addition of water retaining agents, inhibitors, and corn stalks significantly affected the soil available P content in corn seedling stage, in which the application of corn stalks increased the soil available P content, and the addition of PAM, K-PAA, and inhibitors decreased the soil available P content. Only the addition of inhibitors reduced soil available P content in corn jointing stage (Table S4).

Soil Exchangeable Potassium

Soil exchangeable K content changed little during the growing period of corn (Table 5). Corn stalks addition significantly increased the exchangeable K content in corn seedling stage but decreased the exchangeable K content in corn mature stage. The addition of PAM significantly promoted the exchangeable K content in soil at corn mature stage (Table S5).

Table 5. Exchangeable K (mg kg^-1) in Topsoil at Different Growth Stages of Corn

Soil Organic Carbon and Total Nitrogen

As shown in Fig. 2A, the SOC content was about 8.5 g kg^-1, and there was no significant difference in all treatments except that AU treatment was significantly higher than RUIS and AUI treatments. The total N content of soil was about 0.9 g kg^-1, and there was no significant difference among all treatments (Fig. 2B). The addition of water retaining agents, inhibitors, and corn stalks had no significant effect on SOC and total N (Table S6).