Effect of Irrigation and Fertilization on Population Structure and Yield of Wheat

Minmin SHAO Leiming SUN Xingke XU Kai ZHAO Ling HUANG Weiying FENG Jifeng WANG Lu YAN Lin WANG

Abstract [Objectives] This study was conducted to investigate the effects of irrigation and fertilization on population structure and yield of wheat.

[Methods] With Shannong 29 as an experimental material， the effects of irrigation and fertilization on population， dry matter accumulation and yield of wheat were studied.

[Results] Integrated water-saving irrigation and fertilization of ridged field was the best with the highest population， dry matter accumulation and yield of wheat.

[Conclusions] This study provides a theoretical basis for high-yield and high-efficiency wheat production with saved water and fertilizers.

Key words Irrigation; Fertilization wheat; Integration of water and fertilizer; Yield

The Huanghuai River Basin is the main wheat producing area in China. The total wheat production in this area accounts for about 60% of the Chinas total wheat production， but the total water resources account for only 7.7% of the Chinas water resources[1]. Precipitation in the wheat growing season in this area is less than 200 mm， and water evapotranspiration is about 400 to 500 mm. The precipitation can only meet 25% to 40% of the water demand during the whole growth period[2]. Meanwhile， 30% of the arable land in this area has a problem of excessive nitrogen fertilizer application， which not only causes waste of resources， but also environmental pollution[3]. Therefore， water shortage and improper application of nitrogen fertilizer have become the main limiting factors for wheat production in this area.

At present， the research on high-yield cultivation techniques for wheat are mostly limited to the effects of differences in single factors on wheat population and yield under the application of high water and fertilizer or quantitative irrigation[4-5]. However， there are few studies on different irrigation modes and different fertilization treatments. In this study， high yield and high water use efficiency of wheat were realized by the method of precisely supplementing fertilizers and water as required according to the degree of water deficiency in the key growth period and the soil water and natural precipitation conditions in the wheat field; and the effects of different nitrogen application and irrigation methods on wheat population， dry matter accumulation and grain yield were studied to provide a theoretical basis for high-yield and high-efficiency cultivation of wheat with saved water and fertilizers.

Materials and Methods

General situation of research area

This experiment was carried out at the experimental farm of Jining Academy of Agricultural Sciences. The tested soil in the research area was brown soil， which contained soil organic matter content 10.76 g/kg， total nitrogen 0.95 g/kg， available phosphorus 46.92 mg/kg， rapidly available potassium 62.56 mg/kg and alkali-hydrolyzable nitrogen 75.1 mg/kg， and had a pH value of 5.97. The previous crop was maize. The total precipitation during the growth period was 226.5 mm， of which 122.7 mm happened from seeding to jointing， 75.6 mm from jointing to flowering， 28.2 mm from flowering to maturation. The soil bulk density and field moisture content in the 0-100 cm soil layer before sowing of wheat in the growing season are shown in Table 1.

Experimental design

The tested wheat variety was Shannong 29. Five treatments were set up in the experiment： demand-based integrated supplementary irrigation and fertilization treatment （W1）， integrated water-saving irrigation and fertilization of ridged field （W2）， conventional irrigation and fertilization treatment of ridged field （W3）， water blank treatment （W4） and fertilizer blank treatment （W5）. The fertilizer application rates and methods were different for different treatments， and the details are shown in Table 2. Among them， the supplemental irrigation technique based on testing soil moisture was applied for W1 to supplement the average soil relative moisture content in the 0-40 cm soil layer at the jointing stage to 70% using micro-spraying hoses for irrigation. For W1 and W2， dressing in the jointing stage was performed with a portable fertilizer dissolving and injecting machine which applied fertilizers to the field with irrigation water.

The plot area was 2 m×75 m=150 m2. A protection line （2 m in width） was left between different plots， and a protection zone （2 m in width） was set up around the test field. This experiment adopted randomized block arrangement， and was repeated 3 times. Before sowing， all phosphorus and potassium fertilizers and 50% nitrogen fertilizer were applied as the base fertilizer， and the remaining 50% nitrogen fertilizer was applied in the jointing stage. Seeding was performed on October 18， 2016 with a seeding density of 2.25 million plants/hm2. In the three-leaf and one-heart planting stage， final singling was performed， and except W4， the overwintering water was uniformly irrigated; and dressing and irrigation were performed in the jointing stage. Other management measures were the same as those in high-yield fields.

Determination items and methods

Determination of soil bulk density and soil moistur content

A 0-1.0 m soil profile was dug out before the sowing of winter wheat， and the soil bulk density was measured by the cutting ring method at the depths of 0-20， 20-40， 40-60， 60-80， 80-100 cm layer by layer. Soil samples were collected using the 5-point method in each plot. The drying method was used to determine the soil moisture content during the sowing period. The sampling method and operation steps were the same as the sampling method for soil bulk density.

Investigation of population development and dry matter accumulation

Double lines with a length of 1 m were randomly selected in each plot with three repetitions for the investigation of the total stem number and dry matter weight per unit area of the population before overwintering and at the returing green， jointing， flowering and maturiation stages， respectively.

Yield and yield components

At the maturiation stage of wheat， the plants were harvested in the unit of plot， followed by threshing， air-drying and weighing. The grain yield per unit area were calculated， and the 1 000-grain weight was inveistigated. Meanwhile， 30 single ears were taken to investigate the number of grains per ear.

Data processing

Microsoft Excel 2007 and DPS 7.05 data analysis software were used for data collation and statistical analysis.

Results and Analysis

Effects of different treatments on total stem number of the population

As can be seen from Table 1， the total stem number in each treatment group reached the highest during the jointing stage. Among the overwintering， greening， jointing， booting， and maturation stages， compared with other treatments， the total stem number in treatment W5， i.e.， the fertilizer blank treatment group， was the smallest， and treatment W4， the water blank treatment， had the second smallest total stem number. There were no significant differences between treatments W1， W2， and W3. It illustrates the significance of watering and fertilization in wheat production.

Effects of different treatments on dry matter accumulation of wheat

It can be seen from Fig. 1 that the dry matter accumulation of the winter wheat population increased with the advance of the growing period， and it grew slowly from the overwintering stage to the jointing stage， and rapidly from the jointing stage to the maturation stage. The dry matter accumulation ranked as W2>W3>W1>W4>W5 in the overwintering stage. It followed an order of W2>W3>W1>W4>W5 in the revival stage. To the jointing stage， the dry matter accumulation was highest in treatment W2， and lowest in treatment W4. In the booting stage， it was lowest in treatment W5， followed by treatment W4， and treatments W1， W2， and W3 were not much different. In the maturation stage， the dry matter accumulation was in order of W2>W3>W1>W4>W5， and W2 exhibited the highest biological yield. The water blank W4 and fertilizer blank were significantly different from the former three， and the dry matter accumulation of the fertilizer blank was the lowest.

Effects of different treatments on dry matter accumulation and distribution in different organs of wheat at the flowering stage

It can be seen from Table 4 that the accumulation and distribution of dry matter in different organs at the flowering stage were the largest in stems， accounting for more than 60% of the total accumulation. The dry matter accumulation of leaves was the largest in treatment W3 and the smallest in treatment W5， and there was no significant difference between W1 and W2. The dry matter accumulation of stems was the largest in treatment W2， followed by W1. The dry matter accumulation of spike axes and glumes ranked as W5>W4>W3>W2>W1.

Effects of different treatments on dry matter accumulation and distribution in different organs at the maturation stage of winter wheat

It can be seen from Table 5 that the dry matter allocation and distribution ratios of different organs at the maturation stage of wheat ranked as grain>stem + leaf sheath>apike axis + glume>leaf， and the dry matter accumulation in grains accounted for more than half of the total accumulation. The dry matter accumulation of leaves was highest in treatment W3， followed by W1， and lowest in treatment W5. The dry matter accumulation of stems was highest in treatment W2， followed by treatment W3. The dry matter accumulation of grains followed an order of W2>W1>W3>W4>W5. The distribution ratio of dry matter in grains was highest in treatment W1， followed by W2， and lowest in W5. In general， under the W2 and W3 treatments， the dry matter distribution ratio and amount in grains were both at a high level， which was beneficial to the improvement of grain yield.

Effects of different treatments on the translocation of dry matter stored in vegetative organs of winter wheat to gains before and after anthesis

It can be seen from Table 6 that different fertilization and irrigation modes had significantly different effects on translocation， translocation rate and contribution of dry matter stored in vegetative organs before anthesis to grains. The translocation of dry matter stored in vegetative organs before anthesis to grains ranked as W2>W3>W1>W4>W5， and the contribution of dry matter stored in vegetative organs before anthesis to grains was highest in W3， followed by W4. After anthesis， the assimilation of dry matter was maximum in W2 and minimum in W5. The dry matter translocation and its contribution to grain yield after anthesis were largest in W1. It indicated that treatment W1 mainly increased the proportion of dry matter after anthesis and increased its contribution to grains.

Yield and yield components of winter wheat under different treatments

It can be seen from Table 7 that the yield was highest in W2 （integrated water-saving irrigation and fertilization treatment of ridged field） is the highest， followed by conventional irrigation， and demand-based supplementary irrigation next again， but the differences between any two of the three were not large. The yield reductions in W4 and W5 were significant， and the largest yield reduction in W5 illustrated the significance of fertilization in wheat production. The demand-based supplementary treatment had slightly lower yield， but it reduced water by 66 m3/hm2， saving 10% of water， so it was ecologically beneficial. Furthermore， it also saved electricity， and the overall economic benefit did not decreased. Therefore， it should be promoted， especially in areas where water is scarce.

Conclusions and Discussion

Studies have shown that most of the grain yield of wheat comes from the accumulation of dry matter after anthesis and the reallocation of dry matter stored before anthesis， and the soil water condition has a significant effect on the accumulation and distribution of wheat dry matter[6-7]. Moderate limited irrigation can reduce water consumption in wheat fields and improve water use efficiency. It is also conducive to dry matter accumulation， promotion of grain filling， and increase of wheat grain yield[8]. Based on water and fertilizer conservation， we studied the effects of different irrigation and fertilization methods on wheat growth and yield. It was shown that under the same fertilization conditions， compared with the conventional irrigation with furrow dressing of nitrogen fertilizer， the integrated water-saving irrigation and fertilization technique for ridged field could significantly increase the dry matter accumulation after anthesis， was conducive to grain filling at the later stage of flowering and thus increased wheat yield. For integrated water-saving irrigation and fertilization treatment and the demand-based integrated irrigation and fertilization treatment， their water and fertilizer use efficiency were both higher than the conventional irrigation with furrow dressing of nitrogen fertilizer， and the grain yield of W2 was 3.1% higher than the yield of W1， which was 0.5% higher than the yield of W3 in turn. Taking comprehensive consideration of yield and water and fertilizer use efficiency， the integrated water-saving irrigation and fertilization technique with a nitrogen application rate of 240 kg/hm2 for ridged field is the best， and could serve as the appropriate irrigation method for wheat production.

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