Nitrogen Competitive Characteristics Of Hedgerows And Crops On Agroforesty System In Slope Land

Agroforestry is a reasonable land use for development of mountain and hill regions and soil erosion control. Set Vetiveria zizanioides and Amorpha fruticosa as hedgerows and intercropping with wheat/soybean to make the system, crops yield and biomass, nitrogen concentration, uptake of hedgerows and crops were measured. Pot, field plot and isotopic tracer experiments were conducted to study nitrogen competitive characteristics of hedgerows and crops with using some certain formula, The results are as follows:Advantages are different in intercropping systems. The land equivalent ratio of wheat and soybean to hedgerow respectively range from 1.07 to 1.11 and from 0.95 to 0.99 in the system, which shows that wheat is a dominant species with more competent than hedgerows and possessing intercropping advantage, and that of the soybean/hedgerow intercropping is not advantageous, but not significant.Whether intercropping systems have superiority or not, the competitive nitrogen uptake always occurs between crops and hedgerows. Based of the competitive ratio formula of Morris's, we obtained the competitive ability of nitrogen uptake by wheat relative to uptake by hedgerows from the facet of total nitrogen uptake. Under wheat/hedgerow intercropping, the competitive ratio for nitrogen uptake by wheat relative to uptake by hedgerows is 1.06 ?1.18, which demonstrates that the competitive ability of nitrogen uptake by wheat is stronger than hedgerows. Under soybean/hedgerow intercropping, the competitive ratio for nitrogen uptake by soybean relative to hedgerows is 0.84⁰.87, which demonstrates that the competitive ability of nitrogen uptake by hedgerows is stronger than soybean. The isotopic trace techniques directly prove that there lies the competitive uptake nitrogen in soybean/hedgerow systems. The atom % [¹⁵N] excess of soybean and hedgerows was compared in no partition treatment, under soybean/ Amorpha fruticosa intercropping, the atom %[¹⁵N] excesses of soybean and Amorpha fruticosa respectively are 0.341%, 0.399%; under soybeanl Vetiveria zizanioides intercropping, the atom % [^I5N] excesses of soybean and Vetiveria zizanioides respectively are 0.500%, 0.729%, these testify that the competitive ability of nitrogen uptake by hedgerows is stronger than soybean. The [¹⁵N] uptake of soybean and hedgerows by fertilizing [¹⁵N] into soil was compared in no partition treatment, under soybean/ Amorpha fruticosa intercropping, the [¹⁵N] uptake by soybean and Amorpha fruticosa respectively are 1.21 mg/row, 6.42 mg/row; under soybean/ Vetiveria zizanioides intercropping, the 15N uptake by soybean and Vetiveria zizanioides respectively are 4.84 mg/row, 13.9 mg/row, thesetestify that the competitive ability of nitrogen uptake by hedgerows is stronger than soybean.The different competitive ability of nitrogen uptake made different effects in biomass, nitrogen concentration and uptake on species. Impacts of hedgerows on soybean are more than that of wheat, however, with increasing distance impacts of hedgerows on crops decrease and the differences of biomass, concentration, uptake of nitrogen between intercropping and sole cropping systems are not significant. The mechanism is probably that the crop root directly absorbs nitrogen from area of hedgerows, which is the mainly competitive absorbing mode. But the mode is lower that the nitrogen transferring from the root zone of hedgerows to crops through reducing the concentration of the root zone of crops.Nitrogen competitive characteristics of hedgerows and crops are various with different intercropping systems. Compared nitrogen uptake of intercropping systems with sole cropping systems, the whole nitrogen uptake of intercropping systems is enhanced, the nitrogen uptake of the wheat/hedgerow and the soybean/hedgerow intercropping systems respectively are 6%¹9%, 6%⁷% higher than sole cropping systems, and the wheat/hedgerows intercropping systems is predominant than soybean/hedgerows in nitrogen uptake. Compared nitrogen efficiency of intercropping systems with sole crop...