Experimental Study on Water Saving of Large-scale Mechanized Paddy Field Production Process in Heilongjiang Province

Jingfang XUE Shuqiang CHEN Yongsheng CAI Xiaodong DU Limin YANG Haixin ZHAO Tong ZHOU Mingxu ZHOU Linan WANG

Abstract In order to clarify the water-saving technologies and standards in large-scale mechanized production of paddy fields， the water-saving effects and cost-benefit situations of paddy field steeping， seedling transplanting and different land preparation methods were studied. The results showed that the suitable water layer height for the closing period of mechanized operation was 10 cm， which could save water， facilitate weed control， and lead to better effect and the highest yield. The treatment with a water layer height of 1 cm （Huadashui） for the seedling planting operation achieved better quality of seedling transplanting， lower vacancy rate and higher yield and was water-saving. From the perspective of saving water and taking into account the cost of land preparation， the method of steeping and beating the field was better than the method of plowing in autumn and rotary tillage and harrowing in spring， but it was very prone to lodging. From the perspective of high yield creation， the method of plowing in autumn and rotary tillage and harrowing in spring was significantly better than the method of steeping and beating the field. In order to reduce the cost of land preparation， it is recommended to change the way of plowing in autumn and rotary tillage and hallowing in spring to plowing in autumn and rotary tillage in spring or plowing and hallowing in spring to reduce the cost of one time of rotary tillage， and to simultaneously realize deeper plough layer， which is conducive to preventing lodging and obtaining high yield.

Key words Rice; Field steeping; Transplanting seedlings; Tillage and land preparation method; Plowing in autumn and rotary tillage and harrowing in spring; Steeping and beating the field in spring

Rice is one of the main food crops in China. It has a planting area accounting for about 1/3 of the national grain planting area， while the water consumed by rice planting accounts for more than 65% of the national agricultural water consumption[1]. The planting area of rice is increasing year by year， and the demand for water in the process of production and breeding is correspondingly increasing， which intensifies the tension of agricultural water use[2]. Heilongjiang Province is a province with a small amount of water resources in China， and the per capita share of water resources is far below the national average[3-4]. The rice irrigation water consumption in Heilongjiang Province accounts for 96% of crop water consumption. The water-saving irrigation technology in rice-producing areas is an urgent problem to be solved[5]. Choosing an appropriate water-saving irrigation model is of great significance to ensure China's food security and sustainable agricultural development. The peak of rice water demand is mainly during the field steeping and transplanting period from May to June， and the water demand at this stage is about 1/3 of the entire growth period of rice[6]. In addition， two methods are often used in rice field cultivation and land preparation. One is traditional paddy field preparation， and the other is spring field steeping and beating， that is， after steeping the original stubble field for 5-7 d， a paddy field beating leveler is used for the beating operation. The two different farming and land preparation methods have different water-saving effects and cost-effectiveness. Therefore， under the premise of ensuring the increase and stability of rice production， certain water-saving cultivation techniques must be adopted when planting rice[7]， so as to minimize the irrigation water consumption and save more water resources under the condition of ensuring that the current rice planting area remains unchanged. In this study， the changes in indicators closely related to rice production were analyzed through a water consumption standard test for mechanical rice transplanting in steeped field and a water saving effect test of different tillage and land preparation methods， aiming to provide some theoretical basis for the large-scale paddy field steeping， transplanting link， the water-saving standards and cost-benefit analysis of different land preparation methods in Heilongjiang Province， which is extremely important for realizing high- and stable-yielding and high-quality rice production.

Materials and Methods

Experimental materials

The tested rice varieties were Longjing 31 and Longjing 46， which are varieties with 11 leaves in the growth period.

Experimental methods

Water consumption standard tests for mechanical transplanting

In 2017， the water consumption standard test for mechanical transplanting was carried out in the experimental field of the Jiamusi Rice Research Institute of Heilongjiang Academy of Agricultural Sciences. During the field steeping and enclosing period， three test fields of the experimental farm were irrigated with water to 7， 10， and 13 cm， respectively， applied with a enclosing drug and steeped for 5-7 d. Seedlings were transplanted after drainage， and the growth of weeds was investigated during the tillering period to evaluate the weeding effect of the closing drug， so as to understand the suitable height of water layer during the field steeping and closing period and the water saving effect and weed control effect. After steeping and closing the fields， drainage was performed， and a test of appropriate water layer height during the seedling transplanting period was carried out in three test fields， which were set with reserved water layers of 1， 2 and 3 cm， respectively. After transplanting， the vacancy rate and the uniformity of seedlings were investigate to determine appropriate water standards for the transplanting operation and the quality standards for seedling transplanting. In both tests， water consumption was recorded， and yield estimation and laboratory tests were carried out in the maturation stage while calculating the yield and yield components.

Water-saving test of mechanized tillage and land preparation

In 2018， the water-saving effect test of different tillage methods in the process of mechanized operation was carried out in the experimental field of the Jiamusi Rice Research Institute of Heilongjiang Academy of Agricultural Sciences. The test was carried out with two different tillage methods. One was the traditional paddy field preparation （plowing in autumn and rotary tillage and hallowing in spring）， that is， the process of plowing the ground in autumn， dry rotary tillage in spring， applying fertilizer， hallowing with water， leveling， stubble fishing， sedimentation and planting. The other was field steeping and beating in spring， that is， directly beating the field using a paddy field beating leveler after steeping the original stubble field for 5-7 d. A water meter was installed at the inlet and outlet of the test field， respectively， to record the water inflow， drainage during the entire mechanical operation， and water consumption during the entire growth period， The water-saving effect， operation cycle and oil consumption were compared between the two tillage and land preparation methods. Yield estimation and laboratory tests were carried out in the maturation stage， and the yield， yield components and benefit were compared.

Planting area and management

In the experiment， the planting area of each treatment was 2 hm2， and the planting management was the same as the field production.

Determination items and methods

Vacancy rate： The number of seedlings per unit area was measured before transplanting. Two pieces of seedlings of 8 cm×8 cm were cut with soil in each treatment， for the counting the number of seedlings. The number of seedlings per 1 cm2 was investigated. After planting， the 5-point sampling method was used to determine the vacancy rate.

Yield estimation and laboratory test： Three-point sampling was carried out in each repetition， and 6 m2 was taken from each test point. After natural air drying， the yield was measured by threshing. Ten clusters were selected for seed testing， during which the number of panicles and the primary branch number of all panicles were investigated. Ten panicles were selected according to mode to measure the characteristics of panicle length， number of grains per panicle， number of full grains， number of empty grains and so on.

Water consumption： The water inflow and discharge， the operation cycle and the cost of mechanical farming during the entire mechanical operation process were recorded.

Data processing

Microsoft Office Excel 2003 and DPS7.05 software were used to carry out data sorting and difference significance analysis.

Results and Analysis

Comparison of different heights of closing water layers in the steeped fields

It can be seen from Fig. 1 that when the height of the closing water layer in the steeped field was 7 cm， the irrigation water used was 46.7 m3/667 m2; when the height of the water layer was 10 cm， the irrigation water used was 66.7 m3/667m2; and the irrigation water used was 86.7 m3/667 m2 when the height of the water layer was 13 cm. The difference between every two irrigation gradients was about 20 m3/667 m2.

Occurrence of weeds in the steeped fields with closing water layers of different heights

It can be seen from Fig. 2 that the occurrence of Sagittaria trifolia L. var. sinensis （Sims） Makino， Scirpus juncoides Roxb， and Echinochloa crusgalli （L.） Beauv in the field with the closing water layer height of 7 cm at the tillering stage was 5.3， 52.0 and 1.0 plants/m2， respectively; the occurrence of S. trifolia L. var. sinensis （Sims） Makino， S. juncoides， and E. crusgalli in the field with the closing water layer height of 10 cm at the tillering stage was 3.7， 4.3 and 1.0 plants/m2， respectively; and the occurrence of S. trifolia L. var. sinensis （Sims） Makino， S. juncoides， and E. crusgalli in the field with the closing water layer height of 13 cm at the tillering stage was 1.3， 12.3 and 0.7 plants/m2， respectively. The different water layers all had a better control effect on E. crusgalli， but there were large differences in the control effects on S. trifolia L. var. sinensis （Sims） Makino and S. juncoides， and the control effects on S. trifolia L. var. sinensis （Sims） Makino were especially obviously different. Taken together， the treatment with the closing water layer of 10 cm had the best weed control effect， followed by the treatment with the closing water layer of 13 cm. From the perspective of water conservation and weed control， the water layer with a height of 10 cm during the closing period of the fields was the best.

Effects of different closing water layer heights on the yield and yield components of Longjing 46

It can be seen from Table 1 that the yield of Longjing 46 was the lowest when treated with the closing water layer of 7 cm high， at 7 727.7 kg/hm2; the yield was the highest when treated with the closing water layer height of 10 cm， at 10 637.1 kg/hm2; and when the height of the closing water layer was 13 cm， the yield was lower， being 8 242.2 kg/hm2. The yield of the treatment with the closing water layer height of 10 cm in the paddy field was the highest， mainly because the number of panicles of Longjing 46 was significantly higher than those of other two treatments， resulting in a higher number of spikelets per unit area. Different heights of closing water layers in stepped fields had little effect on the rate of fertilized spikelets and the 1 000-grain weight in Longjing 46.

Comparison of irrigation amounts at different water layer heights for transplanting seedlings

It can be seen from Fig. 3 that the irrigation water used for the treatment with the water layer height of 1 cm （Huadashui） was 6.7 m3/667 m2; the irrigation water used for the treatment with a water layer height of 2 cm was 13.3 m3/667 m2; and the irrigation water used for the treatment with the water layer height of 3 cm was 20.0 m3/667 m2. The differences between every two irrigation gradients were about 6.7 m3/667 m2.

Comparison of vacancy rates at different water layer heights for transplanting seedlings

It can be seen from Fig. 4 that the vacancy rate of the treatment with the water layer height of 1 cm （Huadashui） was 3.5%; that of the treatment with the water layer height of 2 cm was 3.4%; and that of the treatment with the water layer of 3 cm was 9.5%. The vacancy rates of the treatments with the water layer heights of 1 （Huadashui） and 2 cm were close， while the vacancy rate with the water layer height of 3 cm was significantly higher than those of other two treatments. From the perspective of water saving and the quality of transplanting， the recommended water layer height for planting operations is 1 cm （Huadashui）; and from the perspective of increasing temperature and cold resistance， the recommended water layer height for planting seedlings is 2 cm because water in the field after transplanting or returning the water in time plays a role of keeping warm and preventing freezing.

Comparison of yields and yield components of Longjing 31 with different water layer heights

Table 2 shows the effect of water layer height in seedling transplanting operations on yield. The yield of the treatment with the water layer height of 1 cm for the transplanting operation was 10 942.0 kg/hm2， and the treatment with the water layer height of 2 cm for the transplanting operation had the highest yield of 10 991.2 kg/hm2. The two values were close， and were both significantly higher than the 3 cm water layer treatment （9 426.9 kg/hm2） for the transplanting operation. The yields of the treatments with the water layer heights of 1 and 2 cm for the transplanting operation were higher， mainly because their numbers of panicles were significantly higher than the treatment with the water layer height of 3 cm for the transplanting operation， resulting in higher numbers of spikelets per unit area. The rate of fertilized spikelets and the 1 000-grain weight in the treatment with the water layer height of 1 cm in the transplanting operation were higher than other two treatments.

Comparison of water consumption and cost between different tillage methods

It can be seen from Table 3 that the water consumption and costs of different tillage and land preparation methods were quite different. The method of plowing in autumn and rotary tillage and harrowing in spring consumed water at 795-900 m3/hm2 when steeping the field， while the method of steeping and beating the field in spring only consumed water 405-450 m3/hm2， and saved water by 345-495 m3/hm2 compared with the method of plowing in autumn and rotary tillage and harrowing in spring. In terms of the cost of mechanical land preparation， there were 3 operations in the method of plowing in autumn and rotary tillage and hallowing in spring， including plowing in autumn， rotary tillage and hallowing in spring， and the cost of land preparation was 1 800 yuan/hm2， while the method of steeping and beating the field in spring only steeped the field for 5-7 d in spring and beat the field once with a paddy field beating leveler， and cost 900 yuan/hm2， saving 900 yuan/hm2 compared with the method of plowing in autumn and rotary tillage and harrowing in spring. In terms of operation cycle， the time consumed by the method of plowing in autumn and rotary tillage and harrowing in spring was longer. In autumn， in addition to harvesting rice and returning straw to the field， it also needs to plow the field in autumn， which requires a large amount of labor in autumn. The time for the spring steeping and beating method was shorter. In spring， in addition to raising seedlings， it also requires spring rotary tillage and beating of the field， so it needs a large amount of labor in spring. It is recommended to change the way of plowing in autumn and rotary tillage and hallowing in spring to plowing in autumn and tilling in spring or plowing and hallowing in spring to reduce the cost of one time of rotary tillage， thereby making the difference between the two methods of tillage and land preparation to 300 yuan/hm2.

Occurrence of lodging with different land preparation methods

It can be seen from Fig. 5 that different land preparation methods had a greater impact on the depth of the cultivated layer and the lodging index. The method of plowing in autumn and rotary tillage and hallowing in spring resulted in a deeper cultivated layer， reaching 17.2 cm， while the direct beating of spring paddy field only produced a depth of 10.8 cm， so the depths were quite different. The difference in tillage depth affects the distribution of rice roots in different tillage layers， which directly affects the lodging of rice. The roots of rice in the method of directly steeping and beating the field in spring were distributed on the surface， while the lodging index of the method of plowing in autumn and rotary tillage and hallowing in spring was 114.8， which was significantly lower than that of the method of direct steeping and beating in spring （128.2）. For lodging-resistant cultivation， it is recommended that the depth of the cultivated layer should be above 15 cm.

Effects of different tillage methods on yield

From Table 4， it can be seen that the yield of rice in the treatment of plowing in autumn and rotary tillage and hallowing in spring was higher， reaching 8 621.8 kg/hm2， while the yield of rice in the method of directly steeping and beating the field in spring was lower， only 8 406.0 kg/hm2. The main reason for the higher yield of rice in the treatment of plowing in autumn and rotary tillage and hallowing in spring was that the number of rice panicles under this treatment was significantly higher than that of the spring field steeping and beating treatment. There were little differences in the rate of fertilized spikelets and 1 000-grain weight between different treatments.

Conclusions and Discussion

Conclusions

From the perspective of water saving and weed control effect， the treatment with the closing water layer height of 10 cm in the steeped field was the best. This treatment saved 20 m3/667 m2 of water in the steeped field compared with the 13 cm treatment， and had better control effects on weeds such as S. trifolia L. var. sinensis （Sims） Makino， S. juncoides， and E. crusgalli. The yield of the treatment with the closing water layer height of 10 cm in the steeped field was the highest， reaching 10 637.1 kg/hm2， which was mainly due to the significant increase in the number of panicles， resulting in a significant increase in the number of spikelets in the population.

From the perspective of water saving and the quality of seedling transplanting， the 1 cm water layer for the transplanting operation （Huadashui） was better; and from the perspective of increasing temperature and cold resistance， the height 2 cm water layer for transplanting seedlings was better， because water in the field after transplanting plays a role of keeping warm and preventing freezing. The vacancy rates in the treatments with the water layer heights of 1 and 2 cm for the transplanting operation were lower， and the yields were higher and close， which was mainly because the numbers of panicles in the two treatments were significantly higher than that of the treatment with the water layer height of 3 cm for the transplanting operation， and the number of spikelets per unit area was higher. The rate of fertilized spikelets and the 1 000-grain weight in the treatment with the water layer height of 1 cm in the transplanting operation were higher than those of other two treatments.

In terms of saving water and taking into account the cost of land preparation， the method of stepping and beating the field in spring saved 345-495 m3/hm2 of water and 900 yuan/hm2 in the cost of farming and land preparation compared with the method of plowing in autumn and rotary tillage and hallowing in spring. However， the cultivating layer of the treatment of directly steeping and beating the field in spring was shallow and caused lodging easily. The yield of rice in the treatment of plowing in autumn and rotary tillage and hallowing in spring was significantly higher than that of directly steeping and beating the field in spring， which was mainly because the number of rice panicles under this treatment was significantly higher than that of directly steeping and beating the field. It is recommended to change the way of plowing in autumn and rotary tillage and hallowing in spring to plowing in autumn and tilling in spring or plowing and hallowing in spring to reduce the cost of one time of rotary tillage， thereby making the difference between the two methods of tillage and land preparation to 300 yuan/hm2.

Discussion

Heilongjiang Province is a major rice province in China and China's main commercial grain base. Its rice output accounts for more than 40% of the province's total grain output， and rice is also the largest water user for agricultural irrigation in the province[8]. There are three aspects of rice irrigation water consumption， namely， the water consumption for steeping the field before transplanting rice， the water consumption during the seedling period， and the water consumption during the field growth period. In the past， the water consumption for cultivation was often discussed， that is， irrigation water consumption. For example， the "shallow， wet， and sun drying" irrigation technology developed in the late 1970s made great progress in the mid-1980s and began to be applied to rice field production， and began to be widely applied in the early 1990s[9-11]. Studies have pointed out that through the application of this irrigation technology for rice， the purpose of saving water for rice can be achieved. Not only will it not reduce the yield of rice， but it can promote the increase of rice yield. Using this irrigation technology in the actual application of rice irrigation can increase the water saving rate by 15% to 20% compared with traditional flooding irrigation[12]. Studies have also pointed out that the use of this irrigation technology can save water consumption by 11.0%-39.6%， and can increase rice yield by 1.1%-35.0%[13-16]. Regarding the water consumption of steeped fields during the seedling transplanting period and the methods of tillage and land preparation， previous studies have obtained many different results： different water consumption has different water-saving effects， and has different effects on rice yield and other growth-related indicators， and the test results obtained in different test areas vary. There are many methods of water-saving cultivation， which are suitable for different areas. Therefore， it is necessary to explore the corresponding water-saving cultivation techniques based on the actual conditions of each area， improve the selection and breed of drought-resistant varieties， and put forward suitable local water-saving cultivation techniques for rice[17-18]. This experimental study found that， from the perspective of water conservation and weed control， the suitable water layer height during the closing period of steeped fields with mechanized operations was 10 cm; and from the perspective of water saving and the quality of rice transplanting， the water layer height of rice transplanting operation less than 1 cm （Huadahui） was the best treatment. From the comprehensive consideration of saving water and taking into account the cost of land preparation and lodging resistance， the recommended way of tillage and land preparation is plowing in autumn and harrowing in spring or plowing and harrowing in spring. Through the water standard test of mechanical transplanting in steeped fields， the water-saving effect test of different tillage and land preparation methods， and the study on the changes of closely related indexes of rice production， we hope to provide some theoretical basis for the water-saving standards and cost-effectiveness analysis of different tillage and land preparation methods in large-scale paddy field steeping and seedling transplanting link in Heilongjiang Province.

References

[1]ZHANG XF， WANG DY， FANG FP， et al. Food safety and rice production in China[J]. Research of Agricultural Modernization， 2005， 26（2）： 85-88. （in Chinese）

[2]MAO Z. Water-saving irrigation in paddy field plays a key role in production increase and pollution control[J]. China Water Resources， 2009（21）： 11-12. （in Chinese）

[3]GAO JD. Path selection of sustainable development of water resources in Heilongjiang Province[J]. Heilongjiang Science and Technology Information， 2008（21）： 130. （in Chinese）

[4]LIU Y， ZHANG YZ， WANG XH， et al. Research status and prospects of rice mulching cultivation[J]. Hunan Agricultural Sciences， 2009（2）： 55-58. （in Chinese）

[5]WANG J， HUANG QB. Application and demonstration of automatic control system for water-saving irrigation in rice fields[J]. Agricultural Modernization， 2016（2）： 22-22， 23. （in Chinese）

[6]JIANG H. Summary of research on water-saving cultivation techniques of rice in North China[J]. Technology and Life， 2011（14）： 93. （in Chinese）

[7]YE WQ， WANG S. Water-saving and high-yield cultivation techniques for rice[J]. Hebei Nongye Keji， 2008（11）： 7. （in Chinese）

[8]LIU CR， ZHAO Y， WANG ZG. Prospects for rice water saving technology in Heilongjiang Province[J]. Heilongjiang Science and Technology of Water Conservancy， 2012， 40（1）： 23-24. （in Chinese）

[9]YU SE， ZHANG ZY. Technical system of water-saving irrigation for rice planting in Jiangsu Province[J]. Journal of Hohai University： Natural Sciences， 2002， 30（6）： 30-34. （in Chinese）

[10]ZHENG YF， YANG LM， ZHAO FM， et al. High-yielding cultivation of rice based on water-saving irrigation and vinyl-film covering in the whole growth period[J]. Heilongjiang Agricultural Sciences， 2001（4）： 17-20. （in Chinese）

[11]ZHANG WY. Vigorously promoting the "thin， shallow， wet， and sun drying" irrigation technology to promote agriculture to a new level[J]. Shanghai Water Conservancy， 1998（z2）： 37-40. （in Chinese）

[12]WANG YS. Irrigation measures for saving water and increasing production of rice[C]//Beijing， China： November 2012 Academic Exchange Conference on Construction Technology and Management. Beijing： 2012. （in Chinese）

[13]ZHANG WY. Application effect of shallow wet irrigation technology[J]. Reclaiming and Rice Cultivation， 1999（3）： 15-16. （in Chinese）

[14]LI CM， GAO Y， TAN SQ， et al. Rice shallow wet water-saving irrigation technology[J]. North Rice， 2001（z1）： 12-13. （in Chinese）

[15]XU H， ZHANG XL. Application and promotion of rice water-saving irrigation technology[J]. Inner Mongolia water conservancy， 2003（3）： 38-40. （in Chinese）

[16]YU Q. Different water-saving irrigation experiments for rice[J]. Journal of Anhui Agricultural Sciences， 2012， 40（36）： 17904-17906， 17970. （in Chinese）

[17]PENG RM， ZHU A， ZHANG SJ， et al. Review on the effects of water-saving irrigation methods on rice yield and paddy soil properties[J]. Jiangsu Agricultural Sciences， 2018， 46（23）： 31-35. （in Chinese）

[18]LI YJ. Formation and development of water-saving rice cultivation technology system in Jiamusi， Heilongjiang Province[J]. Beijing Agriculture， 2015（17）： 10. （in Chinese）