Effects of Straw Returning with Different Tillage Patterns on Corn Yield and Nitrogen Utilization

Dai Jian-jun, Zhang Yu-fei, Wang Xiao-chun, Ma Yu-xuan, and Liu Li-zhi

College of Resources and Environmental Sciences, Northeast Agricultural University, Harbin 150030, China

Abstract: To explore the effects of farming methods, straw returning and their interaction on corn yield and nitrogen utilization,the experiment was conducted for two consecutive years from 2016 to 2017 at the Xiangyang Experimental Base of Northeast Agricultural University in Heilongjiang Province of China. The method of combining farming with straw returning was used and six treatments as rotary tillage (R)+no straw returning (K), rotary tillage (R)+straw returning (S), tillage (T)+no straw returning (K),tillage (T)+straw returning (S), tillage (T)+subsoiling (D)+no straw returning (K) and tillage (T)+subsoiling (D)+straw returning (S)were set to study the effects of different tillage methods and straw returning on corn yield and nitrogen accumulation and utilization.The corn yield, nitrogen accumulation, nitrogen transport, grain weight and dry matter accumulation of tillage (T)+subsoiling (D) and tillage (T) were significantly higher than those of rotary tillage (R) treatment. Meanwhile, the corn yield, nitrogen accumulation and dry matter accumulation of TD treatment were significantly higher than those of T treatment; the corn yield, dry matter accumulation,kernel weight, nitrogen dry matter production efficiency and nitrogen grain production efficiency of S treatment were significantly higher than those of K treatment. Among the treatments, the yield, nitrogen accumulation and utilization efficiency of TDS, TS and TDK were the highest. The yield, nitrogen accumulation and nitrogen transport of TDS were significantly higher than those of TS.In 2016, TDS production increased by 7.30% and 8.20% compared with TS; and TDS nitrogen accumulation increased by 6.78%and 9.50% compared with TS, while the yield and nitrogen grain production efficiency were significantly higher than those of TDK.Therefore, under the conditions of this experiment, on the basis of straw returning, tillage+subsoiling was the suitable farming method.

Key words: tillage pattern, straw returning, corn yield, nitrogen accumulation

Introduction

Corn is one of the most important food crops in China,and its planting area and the total yield rank second in the world. The cultivation method of spring corn planting in the north of China is often rotary tillage,which causes the depth of plough layer becoming shallower, the bottom of the plough becoming harden, the downward extension of the root system is limited and the absorption of nutrients and water is so hindered that these limit the growth and development of corn (Liuet al., 2018; Tubeilehet al., 2003). In the current agricultural production, although China has abundant straw resources, there are still unreasonable utilization of straw, which not only waste resources,but also cause environmental pollution by burning straw. Therefore, it is important to improve the soil structure, improve soil water storage capacity and promote nutrient absorption of crops through suitable tillage method combined with straw returning to field which is of great signi ficance for the grain production and the sustainable utilization of farmland.

Soil tillage and straw returning are two important agronomic measures for fertilizing soil and promoting crop growth. Tillage acts on the soil in different external mechanical forces and fundamentally changes the physicochemical properties of the soil,and regulates the factors, such as water, fertilizer,gas and heat, in the soil to achieve the purpose of increasing crop yield (Zhaoet al., 2014). Studies have shown that subsoiling can reduce soil bulk density of plough layer, improve soil permeability, increase soil porosity and permeability, improve the ability to accept rainwater, improve nutrient use efficiency,regulate soil temperature, improve the ecological conditions of corn root growth and improve the root quality and root surface area of corn in 0-40 cm soil layer, increase the nutrient absorption and stress resistance in the late growth stage of corn and be bene ficial to the transformation and utilization of soil nutrients, effectively increase corn yield (Fanet al.,2016; Gonget al., 2016). The decomposition of straw can significantly increase soil organic carbon content,improve soil physical and chemical properties and biological traits, improve soil fertility and increase crop yield and other effects (Zhouet al., 2012). Straw returning can improve the temperature of the plough layer, keep water and soil moisture and increase crop yield ( Zhaoet al., 2014; Wanget al., 2016).

Nitrogen is an important nutrient element of crops(Luoet al., 2016), which can constitute many organic compounds in crops body and is the guarantee of yield and quality (Liuet al., 2009). Nitrogen is an important condition for biomass accumulation and biomass is the basis for high quality and high yield of crops(Changet al., 2018). Studies have shown that nitrogen can promote plant photosynthesis, increase crop nutrient accumulation, so that the yield and quality can be improved, but low nitrogen stress affects the formation, transport and accumulation of crop photosynthetic products (Yanget al., 2017).

The nitrogen accumulation and utilization of crops can reflect the growth of crops more intuitively.The effects of soil tillage, straw returning and their interaction on nitrogen accumulation, utilization and yield of corn are rarely discussed.

Therefore, in this study, corn yield, dry matter accumulation, kernel weight, nitrogen accumulation,nitrogen transport, nitrogen transport rate, nitrogen dry matter production efficiency and nitrogen grain production efficiency under two factors of tillage mode with straw returning had been explored for two consecutive years. The effects of tillage methods, straw returning and their interaction on corn yield and nitrogen accumulation and utilization were analyzed in order to provide reference for optimizing soil tillage methods and rationally utilizing of straw resources and high yield of corn.

Materials and Methods

General situation of test area

The experiment was conducted in the field from October 2015 to October 2017 at the Xiangyang Experimental Base of Northeast Agricultural University.The test area belonged to temperate continental climate with an annual average temperature of 3.50℃-4.50℃,the effective accumulated temperature of ＞10℃ was 2 600℃-2 700℃, an average annual rainfall of 400-600 mm, an annual sunshine duration of 2 500 h and the frost-free period was 135-145 days. The total nitrogen in the plough layer was 1.13g · kg-1, the available nitrogen was 148.80 mg · kg-1, the available phosphorus content was 28.11 mg · kg-1, the available potassium content was 130.20 mg · kg-1and the organic matter content was 21.30 g · kg-1, pH 7.02.

Test materials

Tested corn varieties: Hezhong 11, 126 days from emergence to maturity. Test fertilizer and application method: a stable compound fertilizer (27-10-13)480 kg · hm-2was applied at the time of sowing.

Test design

The experiment was designed for the split-zone test.The main factor was the farming method. There were three methods: rotary tillage (R), tillage (T) and tillage+subsoiling (TD). The secondary factor was straw treatment, two levels of the total straw returning(S) and straw non-returning (K) were set, a total of six treatments: rotary tillage+straw returning (RS),rotary tillage+no straw returning (RK), tillage+straw returning (TS), tillage+no straw returning (TK),tillage+subsoiling+straw returning (TDS) and tillage+subsoiling+ no straw returning (TDK).

The position and area of each treatment were fixed,and the cell area was 20 m×7.2 m, which was repeated five times. The test was carried out on May 8 of each year, with a plant spacing of 29 cm and a row spacing of 65 cm. Harvesting was carried out on October 10 of each year. Corn fertilization and field management were the same as local general fields. The treatment of straw returning to the field was full return to the field,returning amount was 9 500 kg · hm-2. The straw was smashed to about 5 cm by the straw returning machine and the time to return to the field was one week after the harvest. The straw that was not returned to the field was removed from the test site.

The rotary tillage operation was completed by using the Italian MASCHIO rotary cultivator in different tillage modes. The Norwegian Grand KVERNELAND suspended inverted plough with adjustable tillage depth was used to complete the tillage; after tillage of straw into soil, ISQ-340 type all-round deep loosening machine was used for deep loosening treatment.Among them, the depth of straw returning to field by rotary tillage, tillage and subsoiling treatment was 0-15, 20-25 and 25-30 cm, respectively. Before the start of the test, soil rotation tillage was carried out in the experimental land for a long time and the crop straw was not returned to the field.

Determination items and methods

Five strains of each treatment were randomly sampled at different growth stages of corn and then dried in an oven at 105℃, dried at 75℃ to constant weight, then weighed. Pulverized the dried samples, then mixed and sealed.

The total nitrogen content was determined by H2SO4-H2O2digestion and automatic flow analyzer;the dry weight was measured by drying method; the yield was measured at harvest time and the yield was measured in five typical 20 m2sample areas of each treatment. The grain yield per unit area was measured after natural air drying. Fifteen corn samples were taken for each treatment and the yield components, such as kernel weight and 100-grain weight, were determined.

Nitrogen transport capacity (kg · hm-2)=nitrogen accumulation in vegetative organs during tasseling stage-nitrogen accumulation in vegetative organs at maturity

Nitrogen transport rate=nitrogen transport capacity/nitrogen accumulation in vegetative organs during tasselin×100%

Nitrogen grain production efficiency (g · g-1)=grain weight/total nitrogen accumulation

Nitrogen dry matter production efficiency (g · g-1)=the whole plant dry weight/the total nitrogen accumulation

Data analysis

Data were compiled using Excel 2010 and routinely calculated and the test data were tested for significance signi ficance using SPSS 22.0.

Results

Effects of tillage methods, straw returning and their interaction on corn yield and nitrogen accumulation and utilization

Two-way ANOVA analysis based on two-year test data. It could be seen from Table 1 that the effects of straw returning on the yield, dry matter accumulation,kernel weight, nitrogen dry matter production efficiency and nitrogen grain production efficiency were significantly different; the farming method could significantly affect other indicators, such as nitrogen transport rate and nitrogen grain production efficiency.The interaction between the two had significant effects on yield, nitrogen accumulation, dry matter accumulation, kernel weight, nitrogen transport and nitrogen grain production efficiency.

Effects of tillage methods and straw returning on nitrogen accumulation in corn

It could be seen from Table 2 that the nitrogen accumulation in different tillage methods was ranked as TD＞T＞R and the effect of TD treatment on the nitrogen accumulation of corn reached signi ficant level(p＜0.05). Compared with R treatment, TD and T in the tasseling stage increased by 23.32% and 13.50%,and the maturity period increased by 10.47% and 5.41%. In 2017, TD and T treatments in the tasseling stage increased by 14.20% and 6.56% compared with R and the maturity increased by 24.96% and 10.68%.At the same time, the nitrogen accumulation of S treatment was higher than that of K, but did not reach a significant difference. The effects of tillage and straw returning on nitrogen accumulation could reach signi ficant difference (p＜0.05) and in the mature stage of 2017, TDS and TS treatments increased by 38.95%and 24.48% compared with RK, which indicated that the combination of rational tillage and straw returning to the field could significantly increase the nitrogen accumulation of corn in the middle and late stages of high nutrient requirements.

Table 1 Effects of tillage methods, straw returning and their interaction on yield, nitrogen accumulation, dry matter accumulation, kernel weight, nitrogen transport, nitrogen transport rate, nitrogen dry matter production efficiency and nitrogen grain production efficiency

Table 2 Effects of tillage and straw returning on nitrogen accumulation in corn (kg · hm-2)

It could be seen from Table 3 that in different tillage methods, the nitrogen transport capacity of corn was TD＞T＞R, in 2016, TD and T treatments increased by 28.10% and 23.54% compared with R; in 2017, it increased by 27.79% and 7.22% and reached signi ficant difference (p＜0.05).

At the same time, the nitrogen transport capacity of straw returning to the field was higher than that of non-returning, but the effect was not significant and the result was similar to the nitrogen accumulation.In the two years, TDS and TS treatments increased by 33.79%, 24.63%, 31.96% and 8.74% compared with RK and the effect of TDS on nitrogen accumulation reached a significant difference (p＜0.05), indicating that straw returning to subsoiling could improve better.

Table 3 Effects of tillage and straw returning on nitrogen translocation and production efficiency of corn

Corn nitrogen transport rates of TD and T were higher than those of R treatment. Returning straw to the field did not increase the nitrogen transport rate. TDS treatment was higher than RK. Because subsoiling and straw returning to the field not only increased the nitrogen transport capacity, but also increased the nitrogen accumulation of vegetative organs during the tasseling period, the effects of tillage and straw returning on the nitrogen transport rate of corn did not reach signi ficant difference.

The nitrogen dry matter production efficiency of T treatment was the highest in different tillage methods,indicating that tillage could better increase the ratio of dry weight of the whole plant to the total nitrogen accumulation of the whole plant. Because S treatment significantly increased the dry matter weight, but could not significantly affect the nitrogen accumulation, the effect of straw returning on the dry matter production efficiency of nitrogen reached a signi ficant difference(p＜0.05). Straw returning significantly increased nitrogen grain production efficiency (p＜0.05), while tillage did not significantly affect nitrogen grain production efficiency, although TD and T treatments increased grain yield and the total amount of nitrogen accumulation, it did not significantly increase the ratio between the two.

Effects of tillage methods and straw returning on dry matter accumulation of corn

It could be seen from Table 4 that in different farming methods, the dry matter accumulation of corn was ranked as TD＞T＞R, in 2017, TD and T were increased by 14.29% and 8.80% in the seedling stage; 28.07%and 19.13% in the tasseling stage; 26.77% and 16.46%in the maturation period compared with R treatment.Straw returning treatment was higher than no straw returned to the field and TDS treatment was the highest. TDS and TS were increased by 29.44%,39.79%, 27.08% and 32.08% in subsoiling, tillage and straw, respectively compared with RK. The interaction among the field and the two had a significant difference on the dry matter accumulation of corn.

Effects of tillage methods and straw returning on corn yield and yield components

It could be seen from Table 5 that in different tillage methods, kernel weight was arranged in order of TD＞T＞R. The kernel weight of the straw returned to the field was higher than that of no straw returned to the field. In the two years, TDS and TS increased by 14.09%, 11.55%, 13.54% and 8.53% compared with RK treatment. Tillering, subsoiling and straw returning could increase the kernel weight and reach a signi ficant difference (p＜0.05).

Table 4 Effects of tillage methods and straw returning on dry matter accumulation of corn (kg · hm-2)

Table 5 Effects of tillage and straw returning on corn yield and yield components

The size of 100-grain weight of corn was arranged as TD＞T＞R and the returning of straw to the field also increased the100-grain weight, but the effect of the two on the 100-grain weight did not reach signi ficant difference. Corn biomass of TD in 2016 increased by 8.4% and 6.24% compared with R and increased by 26.77% and 16.46% in 2017. The yield of corn under different tillage methods was ranked as TD＞T＞R.In 2016, TD and T increased by 10.87% and 5.36%,respectively compared with R and increased by 17.19%and 11.45% in 2017. At the same time, the corn yield from straw returning to the field was higher than that in the field. The effects of subsoiling and straw returning on the corn yield were significantly different(p＜0.05). The yield of corn treated with TDS was the highest and RK was the lowest in the two years. Under the same farming method, the yield of TDS was the most obvious compared with TDK and the difference was significant, while TS was not significantly different from TK and RS compared with RK. It could be seen that subsoiling tillage combined with straw returning could better increase corn yield.

Discussion

This study showed that subsoiling and tillage treatments could significantly increase nitrogen accumulation in corn, promote dry matter accumulation, increase nitrogen transport and promote the accumulation of nitrogen in stems and leaves to the grain, thereby in-creasing kernel weight and yield, which was consistent with previous research results (Zhaoet al., 2014; Konget al., 2014; Zhanet al., 2014). Subsoiling and tillage could increase the nitrogen accumulation and yield of corn. The reason was that tillage could effectively break the bottom of the plow and directly turn the soil into contact with the outside world, which was conducive to the maximum acceptance of rainwater and subsoiling reduced soil bulk density, increased the microbial activity, promoted the down-pricking of the corn roots and improved the utilization efficiency of water and nutrients (Iqbalet al., 2008; Ding and Hann, 2000).

This study showed that straw returning significantly increased the dry matter accumulation and grain weight of corn and increased nitrogen grain production efficiency and nitrogen dry matter production efficiency, thereby increasing yield, which was consistent with the results of Zhanet al(2014). Straw returning could improve the nitrogen use efficiency and yield of corn, it was because the returning of straw to the soil was bene ficial to increase soil nutrient and organic matter content, which affected crop growth.This view was generally accepted (Blanco-Canqui and Lal, 2007; Laoet al., 2003). In addition, this study showed that straw returning to the field failed to significantly increase nitrogen accumulation and nitrogen transport in corn. The reason for the analysis might be that the straw returning to the field returned nitrogen to the soil, increased the soil microbial biomass C/N and alleviated the soil nitrogen loss(Zhanget al., 2010). As a typical nitrogen-loving crop, nitrogen was an important factor limiting its growth and development (Jianget al., 2011).Increasing nitrogenuse efficency might reduce the fertilizer utilization rate, cause waste of resources, and as the rainfall goes on, it could cause the downward migration of soluble organic nitrogen in the soil,causing a potential environmental pollution risk (Jianget al., 2016; Gaiet al., 2018). Therefore, the straw returned to the field could ensure sufficient nitrogen supply during the growth of the corn.

The depth of rotary tillage+straw returning to the field was only 0-15 cm, which reduced the emergence rate of corn and affected the growth quality of seedling stage, while the depth of tillage+subsoiling+straw returning could reach 25-30 cm, thus the problems,such as soil water loss and soil moisture loss, were effectively avoided (Xuet al., 2018). At the same time,tillage+subsoiling+straw returning could significantly affect 0-40 cm of soil, improve soil physical and chemical properties, promote water and nutrient absorption and increase corn yield (Yuet al., 2018).

This study showed that tillage and straw returning significantly interacted with corn yield, nitrogen accumulation, dry matter accumulation, kernel weight,nitrogen grain production efficiency and nitrogen transport. The corn yield and nitrogen accumulation and utilization were significantly higher than those of rotary tillage+no straw returning, but did not significantly affect the 100-grain weight. Among the treatments, TDS, TS and TDK had the highest yield,nitrogen accumulation and utilization efficiency; the yield, nitrogen accumulation and nitrogen transport capacity of TDS were significantly higher than those of TS, while yield and nitrogen grain production efficiency of TDS were significantly higher than those of TDK, TDS treatment could provide sufficient nitrogen for corn, significantly improve nitrogen use efficiency and increase yield, which was consistent with the results of Guoet al(2016). Due to the low temperature and insufficient rainfall in the test area after the planting in 2017, the corn emergence and growth were affected. As a result, the corn yield and nitrogen accumulation and utilization in 2017 decreased compared with those in 2016.

Conclusions

In summary, under the conditions of this experiment,two years of experiments had shown that ploughing+subsoiling+straw returning could significantly increase corn yield and increase nitrogen accumulation and nitrogen transport of corn compared with other treatments. Therefore, from the perspectives of increasing production productivity, rational use of straw resources,increasing nitrogen utilization rate and reducing environmental pollution risks, plowing+subsoiling+straw returning was the best recommended planting method in this region.