Study on the Trend of the Content of Soil Moisture and Alkali―Hydrolyzable Nitro
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Abstract. With the rapid development of animal husbandry in Inner-Mongolia Autonomous Region， the traditional technology of forage grass plantation can not meet the need of the rapid development of livestock breeding. High efficiency plantation model is badly needed. This experiment put forward the following models such as 1：1 interleaving intercropping， algonquin monoculture （CK1） and atheraless Bromus japonicus monoculture to obtain relative date for analysis. The results showed that mixed cultivation of the Leguminosae alfalfa and gramineae atheraless Bromus japonicus can make full use of the soil moisture and increase the capacity of water holding. During the period of alfalfa seedling establishment， bifurcation， squaring stage， flowering phase， the mixed cultivation of alfalfa and atheraless Bromus japonicus can achieve more moisture in the 0-90 cm soil layer than monoculture and the result of alfalfa monoculture was better than that of atheraless Bromus japonicus monoculture. Meanwhile， intercropping and mixed cropping can stimulate biological nitrogen fixation. During the period of seedling establishment， the content of alkali-hydrolyzable nitrogen in the 0-90 cm soil layer was 36.4 mg/kg and 50.4 mg/kg respectively higher than the content of alkali-hydrolyzable nitrogen achieved by mixed cultivation and interplant of alfalfa and atheraless bromus japonicus. And during the bifurcation stage， the content of alkali-hydrolyzable nitrogen in the 0-90 cm soil layer was increased by 13.3 mg/kg and 7.5mg/kg respectively. The yield thanks to mixed cultivation and intercropping was obviously greatly increased compared with monoculture. The output from intercropping was increased by 5.75% and 37.20% respectively compared with the output from monoculture of alfalfa and atheraless bromus japonicus. The output from mixed cultivation was increased by 7.85% and 57.32% respectively compared with the output from monoculture of alfalfa and atheraless bromus japonicus. The output from mixed cultivation was higher than that from intercropping.
Keywords： Mixed Cultivation Intercropping； Content of Soil Moisture； Alkali-hydrolyzable Nitrogen
1. Introduction
Inner Mongolia Autonomous Region is the largest among China's five major pastoral areas. With the rapid development of the animal husbandry in the Inner Mongolia Autonomous Region， the traditional technology of forage grass plantation cannot meet the need of the rapid development of livestock breeding. Therefore， a plantation model with high efficiency is bad needed. Practice has proven that the productivity， quality and endurance of grassland can be improved by the intercrops of forage grasses. In this experiment， the changing trend of the contents of soil moisture and alkali-hydrolyzable nitrogen in the intercropping and mixed cultivation of leguminosae and gramineae pasture grass is studied， thus providing a theoretical and technical support for the highly-efficient plantation model of forage crops in Inner Mongolia Autonomous Region.
2. Materials and Methods
2.1. Experimental materials
Alfalfa was used as leguminosae experimental material. Atheraless bromus japonicus was selected as gramineae pasture grass material.
2.2. Basic conditions of experimental site
The experiment was made at the teaching farm of Inner Mongolia Agriculture University （NS-40°48′； EL-111°42′； altitude-1063m）. Here， annual average temperature is 5.4 ℃； the highest and the lowest temperatures are 36.9 ℃ and -33 ℃， respectively； average annual rainfall is about 400 mm and mainly concentrated in July， August and September； the frost-free period is140d； soil has deep layers and contains 1.18%， organic matter， 102 mg/kg alkali-hydrolyzable nitrogen， 20.26 mg/kg available phosphorus， and 140 mg/kg available potassium， and its pH is 7.7.
2.3. Experimental design
In the experiment， four groups were set： （1） mixed cultivation of alfalfa and atheraless Bromus japonicas in the same line； （2） 1：1 interleaving intercropping； （3） alfalfa （algonquin） monoculture （CK1）； （4） atheraless Bromus japonicus monoculture （CK2）. The seeding rates of CK2 and CK1 were 1.75kg/MU and 1kg/MU， respectively； in the mixed cultivation of alfalfa and atheraless Bromus japonicas， seeds of alfalfa and atheraless Bromus japonicas were evenly mixed based on 80% of their own monoculture rates. The row spacing of CK1 and CK2 from the mixed cultivation was 0.3 m； the length of row was 5.7 m； the total area was 23.94 m2. Seed manures of monoculture and mixed cultivation were implemented with DAP （diammonium phosphate） according to the ratio of 15 kg/MU.
2.4. Experimental methods
2.4.1 Measurement of soil moisture content
Mixed soil sample of 0-90cm was taken by earth boring auger for three times respectively， and then put in an aluminum box to dry. Then， moisture content in the dried soil samples was calculated with weight difference method.
（1） Where soil samples were taken from： The center of the central row of mixed cultivation area， CK1 and CK2， respectively
（2） When soil samples were taken： Seedling stage， branching stage， squaring stage， initial bloom stage， and pre-overwintering of alfalfa
2.4.2 Measurement of alkali-hydrolyzable nitrogen content
Mixed soil sample of 0-90cm was taken by earth boring auger for three times respectively， and kept to dry in shade place of laboratory. Then， Alkali-hydrolyzable Nitrogen content was measured with alkali-hydrolyzed diffusion method.
（1） Where soil samples were taken from： The center of the central row of mixed cultivation area， CK1 and CK2， respectively
（2） When soil samples were taken： Seedling stage， branching stage， squaring stage， initial bloom stage， and pre-overwintering with the growth stage of alfalfa as benchmark
2.5. Data analysis
Data is analyzed with SAS6.0.
3. Result and Analysis
3.1. Change of soil moisture in intercrop and mixed cultivation of alfalfa and atheraless bromus japonicus
Soil moisture is the basic living condition of plant. Generally， to make the dry matter of a plant， the moisture of 300-500 times is necessarily consumed. Therefore， it can be seen that the moisture needed by plant is considerable.
Moisture contents of intercropping groups of alfalfa and atheraless Bromus japonicus at the soil layer of 0-90cm at different growing stages are compared in table 1： the intercropping and mixed cultivation are higher than the monoculture in moisture content， and CK1 is higher than Atheraless Bromus Japonicus monoculture； the mixed cultivation is higher than intercropping during the period of seedling establishment， and the intercropping is higher than the mixed cultivation during squaring stage and branching stage. Soil moistures at 0-90 cm soil layer during the period of seedling establishment and the branching stage are 13.04%， 3.89% higher than that of CK1， respectively； soil moistures at 0-90 cm soil layer during squaring stage and initial bloom stage are 16.89% and 10.02% higher than that of CK1.
3.2. Change of alkali-hydrolyzable nitrogen in intercrop and mixed cultivation of alfalfa and atheraless bromus japonicus
Alkali-hydrolyzable nitrogen is an important index of available nitrogen in soil and can reflect the supply of soil nitrogen recently. The amount of alkali-hydrolyzable nitrogen is directly related to crop yield. From table 2， it can be seen that as the growing goes on， alkali-hydrolyzable nitrogen content of the mixed cultivation of alfalfa and atheraless bromus japonicus decreases significantly from seedling establishment to initial bloom stage of the first cradle； the total alkali-hydrolyzable nitrogen content at the soil layer of 0-90cm before overwintering is lower than that in seedling establishment. At different growing stage， the rising D-value of alkali-hydrolyzable nitrogen content of CK1 at the soil layer of 0-90cm is higher than declining D-value. Therefore， the total alkali-hydrolyzable nitrogen content at the soil layer of 0-90cm before overwintering is higher than that in seedling establishment； the total alkali-hydrolyzable nitrogen content of CK2 at the soil layer of 0-90cm decreases as growing goes on， but is lower than that of other groups before overwintering. Alkali-hydrolyzable nitrogen contents of the intercropping and mixed cultivation of alfalfa and atheraless bromus japonicas at the soil layer of 0-90cm in seedling establishment increase 36.4 mg/kg and 50.4 mg/kg more than CK1， respectively； alkali-hydrolyzable nitrogen contents in branching stage increase 13.3 mg/kg and 7.5 mg/kg more than CK1， respectively.