Effect Of Long-term Fertilization On Soil Properties And Its Productivity In Rain-fed Field In The Northern Ecotone

This study was carried out in a long-term fertilization experiments （established in2004） in theNorthern ecotone of Yinshan Mountain, using field test, chemical analysis and statistical analysis toevaluate the soil properties&carbon balance, crop productivity&nutrient use efficiency and the netprimary productivity （NEP） in farmland under potato-canola–oat rotation system by4treatments: a)chemical fertilizer NPK plus organic manure （NPKM）, b) organic manure fertilizer （M）, c) chemicalfertilizer （NPK）, and d) no fertilizer （CK）. The main results showed as following:（1）. For9consecutive years fertilization （NPKM, M, NPK）, the same processing of soil availableN, P, K and organic matter content showed an increasing trend year by year, under long-termfertilization system, except that potassium was maintained at a relatively stable level, other nutrientswere slowly declining. Compared with the CK （average9years）, NPKM and M treatment significantlyincreased soil available N, P, K and organic matter content, NPK treatment alone significantly increasedthe available N and K content, wherein, the largest incremental NPKM. The profile distribution ofnutrients from the soil, compared with CK,3fertilization measures were increased soil available N, Kin0～100cm, available P in0～40cm and organic and microbial biomass carbon content in0～20cm.（2）. Potato planting season （2010）, soil carbon emission rate had obvious diurnal and seasonalvariation, the lowest during6:00-8:00and the highest during12:00-14:00; in a year, the maximum inJuly, the period of rain and heat and crop quickly growing. Average CO₂emission rate was94.5～126.5mg C m^-2 H-1in crop growing period and,40.7～51.2mg m^-2 h-1after crop harvest. The diurnalvariation of carbon emission rate was influence by10cm soil temperature, Q10=1.47～1.68; Seasonalvariation of carbon emission rate was influence by soil temperature in10cm, soil moisture in0～20cmand crop growth, where carbon emission rate was positive with crop growing and accumulation ofpotato tuber dry matter, and significantly positive correlation with10cm soil temperature after harvest.Compared with the control, fertilization increased soil CO₂emission rate, the order of M>NPKM>NPK.（3）. In the north of Yinshan Mountain rain-fed farmland, CO₂emissions was2.17～3.29t C·hm^-2during crop growing period, and yearly total CO₂emissions was2.81～4.28t·hm^-2. Compared with thecontrol, the largest incremental from M, followed by NPKM and NPK. If carbon emissions was onlyconsidered during crop growing period, the absorption of CO₂from the atmospheric was0.11～0.81tC·hm^-2, and the farm system absorbed0.087and0.21t C·hm^-2from the atmosphere each year if carbonemissions was considered in the whole year. Soil carbon balance showed deficit in NPKM and Mtreatments.（4）. An average of9years, different fertilization measures increased potato yield26.1～44.2%，and canola yield27.9～97.5%and oat yield22.7～38.7%than the CK, NPKM was the highest,followed by NPK and M. The average N. P2O5, K2O nutrient agronomic efficiency were8.6,8.3and7.9 kg·kg-1. The same nutrient variation in a year was mainly affected by crops, and potato was the highestone. Average N, P2O5, K2O nutrient utilization rate in one growing period were45.3%,20.7%and54.5%. In8-year trails, N seasonal utilization increased linearly with rainfall in growing period.