Study On The Foundation And Application Of Macromolecule Materials For Plants Growth In Dry Land

Drought as a worldwide problem results in serious grain production loss whichhas surpassed the total loss caused by other nature disasters. The arid and semiaridfarm belt is about 52.5ï¼…of the earth land in our country, among which the plowlandis 51 million hm~2 and is about 51ï¼…of all plowland in our country. The dry landwithout irrigation is about 65ï¼…of the and and semiarid farm belt. Three seriousenvironment problems of the soil erosion, desertification and salinization in the aridand semiarid area not only endanger the throughput and the stability of the dry landfarming, but also jeopard the country ecosystem security.From the point of view of agriculture, great effort and achievement has beenmade to the dry farming science and technology. However, low-output, instability andbad-profit still remain bothering. In recent years, the water-retaining technology withmacromolecular material has become a remarkably new direction for the dry farmingtechnology. However, there are still many important scientific problems to be unclear.With the dry farming research and the application of water-retaining materialexamined from the point of view of material science, it can be found that the mainproblems are: (1) the limited research method with little cross-discipline, and (2) theabsence of deep theoretical research on the behavior of the macromolecularwater-retaining material in real soil. For example, although the concept of "water andfertilizer coupling" is put forward, the technique to completely realize it cannot begiven out as the coupling mechanism is scarcely studied. Also, although thewater-retaining material is used, its effect cannot be fully displayed as its processingmechanism in the soil is scarcely studied. Meanwhile, although the important role ofthe flourishing root system on the water and fertilizer is known, the knowledge andthe method to effectively promote the root growth is scarcely studied. With thewell-known theory and method in the materials science and technology, this papertries to investigate the physicochemical mechanism and the transportation anddistribution discipline of the macromolecular water-retaining material applied to thedry farming.According to the present situation of dry farming research and practice, it is thought that in order to increase the dry farming yield, the water-retaining materialmust be scientifically applied to bring it into fullplay. Thus the basic thought of thispaper is the scientific application of the macromolecular water-retaining material.First, the water retention mechanism in the dry farming soil is amply investigatedwhile the water and the nutrient transmission discipline are studied. Then, the newtechnique to realize sufficient water and fertilizer coupling with crop growth isproposed. The corn which is the typical crop in the northwestern dry farming area ischosen to be the experimental crop to test the validity of the research, which can alsobe a very good example to demonstrate the advancement of the dry farming scienceand technology. The aubergine growing in the greenhouse is further chosen to be theexperimental crop to demonstrate that the new technique is also helpful to remarkablyincrease output but decrease cost even with ample water and fertilizer.The main experimentals of this thesis are the following:1. To the land for growing field crops, the soil moisture increase mechanism of themacromolecular polymer with different molecular structure, quantity and employmethod is studied.2. To the salt or nutrient solution with different concentration, the liquid absorptionability of the macromolecular polymer with different molecular structure andquantity is studied.3. According to the morphology character of the macromolecular polymer withdifferent molecular structure after liquid absorption, the relationship between thepolymer, the soil, the moisture and the nutrient is studied.4. With the moisture and main nutrient in the local soil synchronously increased, thewater and fertilizer coupling and balance in the range of the crop root system is tobe realized.5. To the specific crop, the nutrient necessity, the time of maximum benefit offertilization, and the actual distribution of the root system in the soil, the effects ofthe macromolecular polymer and inorganic nutrient compound on the crop growthand yield are studied.The main achievements of this thesis are the following: 1. It is found that the native water absorption character of water-retaining material isdifferent from its practical absorption and retention character of the soil moisture.The present method to evaluate the water absorption character by the deionizedwater quantity absorbed by the material is nonscientific as this index cannot showthe real effect of soil water absorption and retention of the water-retaining material.The research result indicates that the liquid absorption quantity is decreased withthe solution salinity increase to all kinds of macromolecular water-retainingmaterials with different molecule structures, while the decrease to the reticularmacromolecular polymer is quite larger than that to the linear macromolecularpolymer. In the inorganic nutrient solution, the liquid absorption quantity of thelinear macromolecular polymer is much more than that of the reticularmacromolecular polymer.2. It is found that the linear macromolecular polymer is much fit for water-retainingmaterial in the dry fanning compared with the reticular macromolecular polymer.The main reasons are the following. (1) The soil water retention of the linearmacromolecular polymer is much better. The local soil moisture content increasedby unit linear macromolecular polymer is about 20 times of that increased by unitreticular macromolecular polymer. (2) With the linear macromolecular polymerhydrosol uniformly distributed in the soil, the diffusion transportation of moistureand nutrient is effectively constrained. However, the reticular macromolecularpolymer is distributed in the soil in the gel form with less dispersivity anduniformity. (3) The linear macromolecular water-retaining material is helpful toform the soil aggregate and surface structure which is benefit to the dry land cropgrowth. (4) The output increase by the reticular macromolecular water-retainingmaterial can only be realized under the condition of enough irrigation whichcannot be satisfied in the dry farming area. However, the linear macromolecularwater-retaining material needs only a little bit irrigation which can be easilyrealized by manual irrigation in the dry farming area. (5) Since obvious waterretention can be obtained with very small quantity of linear macromolecularwater-retaining material, the production cost can be evidently decreased.3. With the linear macromolecular water-retaining material, the water and fertilizercoupling and its coupling with crop growth are all well realized, which promotesthe remarkable yield increase under the condition of low level of water and fertilizer with small quantity of water-retaining material. (1) The "slow-releasetechnique of liquid compound fertilizer" is established. With the readily availablenutrient diffusion restrained by the linear macromolecular polymer, the nutrientcumulated in the soil and then used as the release source, is slowly absorbed andutilized by the crops. By this means, the readily availability of the liquid nutrientand the balance of the top dressing are all realized, while the nutrient requirementfrom the crops at the given growth period is satisfied. (2) With the slow-releasetechnique and the positioned deep-placement technique of liquid compoundfertilizer, the nutrient diffusion and distribution in the soil is changed, so the soilnutrient enrichment and balance level are all enhanced. The durative yieldincrease is realized as the non-scientificity and blindness of fertilization isovercome. (3) Under the condition of lean soil with bad nitrogenous fertilizerretention, the active nitrogen content of local soil is increased by 87.3ï¼…, whichmeans that the soil active nitrogen content can be increased by a relatively largeextent with the linear macromolecular polymer. (4) The crop root system growthcan be facilitated through several important couplings, such as the water andfertilizer coupling, water/fertilizer and crop coupling, and nutrient provision timescoupling. (5) At the time of maximum benefit of fertilization, the lack ofphosphorus and nitrogen which always restricts the yield increase of the dry landcrop is solved. The corn production of the dry farming test region reaches800kg/667m~2, which is 200kg/667m~2 above the maximum production in theregional history. (6) With the slow-release technique of liquid compound fertilizerapplied to the anti-seasonal vegetable in the sunshine greenhouse, the continuousoutput is increased by 30ï¼….The water absorption macromolecular polymer is another important agriculturalmaterial after the chemical fertilizer, the agricultural chemical and the mulch plasticfilm. Its development must be based on the foundation of the agriculture productionand income increase. The agriculture development especially the dry farmingtechnology advancement depends upon the industrial new material research andapplication. The harmonious development of them is always an important task.