Catch Crop Control Soil Nitrogen Accumulation And Leaching In Greenhouse

This research, adopting Sweet corn (Zea mays L.), Amaranth (Amaranthus spp.)and sweet sorghum(Sorghum Linn.)as catch crops, studies different categories of catch crops as well as their control measures in root zone to carry on the field home position repairing experiments. With decreasing soil nitrate accumulation and leaching in root zone as a target, this research analyzes different categories of catch crops and the influence of control measures in root zone NO₃-N leaching, and reveals their influence on crop yield in the next quarter and soil profile NO₃-N, main results as follows:(1)The sweet corn was the best in biomass , N uptake, and the effect of soil profile NO₃-N reduction, with the reduction of NO₃-N being respectively 153.76 kg/hm2 and 605.70kg/hm2 in 2008 and in 2009.So from the perspective of balance of nitrogen, the loss of two quarters of catch crops 0-200cm soil NO₃-N was the highest in the terms of fallow; compared between the three kinds of catch crops, N loss planting with sweet corn was lowest in 2008, and then that of Amaranth in 2009 was the lowest, but there was little difference in that of Sweet corn.(P<0.05).This result can explain that the growth of the Sweet corn could decrease accumulation of vegetable soil NO₃-N.(2)About biomass and N uptake with the measures of conditioner and straw have not substantial differences, but higher than measures of deep plowing. The accumulation of NO₃-N in soil profile after harvest of catch crop with the measures of fallow was the highest. Accumulation of NO₃-N with the measures of fallow was 90-100cm,while fallow was 120-140cm.In the variety of soil profile accumulation of NO₃-N, fallow was always in high residue. The effect of the three kinds of root layer conditioning agent on NO₃-N could fall in the large bugle stage of sweet corn(after planting 40 days)in NO₃-N,and maintains till harvest,but there was a peak at straw returning 60 days after sewing,from impact of depth we can see that the effect of conventional cultivation reaches 60cm,while conditioning agent and straw returning arrive at 80cm.(3)The trend of leaching amount of water and NO₃-N was similar. That in 2008 was higher than that in 2009, corresponding with raining in 2008.â‘ compared with different kinds of catch crops,NO₃-N leakage of Sweet corn Amaranth and sweet sorghum was 1.9 kg/hm²,2.4 kg/hm²and 2.6 kg/hm² respectively in 2008,compared to fallow, that decrease by 47%,35% and 28% respectively;leaching reach 1.4 kg/hm²,1.3 kg/hm²,3.0 kg/hm² and 5.1 kg/hm² respectively in 2009; the content of NO₃-N in the leakage was not falling in the first quarters of fallow,but in second quarters,which was lower than that before planting clearly,the control measure of Sweet corn was the lowest.â‘¡compared with different control measures,NO₃-N leakages with three kinds of control measures in 100cm of soil root layer were reduced by 47%,83% and 74% separately than fallow treatment, and the leaching amount was lowest in soil structure conditioner treatment;in 2009, conventional cultivation was lower than fallow,while other two treatments were higher than treatment with catch crop,the effect of root layer conditioning agent and straw returning to low NO₃-N leaching was the best in second quarters.(4) In The effect of succeeding cucumber yield,N uptake and biomass of different kinds of catch crops and root layer conditioning agent, previous crops were always the best,without too clear difference. When cucumbers were harvested,all the treatment 0-200cm the accumulation of soil NO₃-N was negative,that of Amaranth was the highest,and followed by that of sweet sorghum,and that of fallow and Sweet corn has not clear difference;the accumulation of soil NO₃-N of root layer conditioning agent was less than that the measures of conventional cultivation and straw returning in apparent in the nitrogen balance,previous fallow NO₃-N losing was the lowest,compared with previous Sweet corn and root layer conditioning agent, without significant difference. In soil profile 100cm, the content of NO₃-N varies not too much, and the trend of treatments change was similar,which shows after cucumber,soil content of NO₃-N in 100cm was still under influence of previous crop,and catch crops provide nitrogen effect until the end of cucumber. At This point, leakage previous fallow Sweet corn,Amaranth and sweet sorghum arrive at 14.14 kg/hm²,6.70 kg/hm²,9.89 kg/hm² and 7.40kg/hm² respectively. The measures of previous fallow conventional cultivation, root layer conditioning agent and straw returning reach 14.14 kg/hm²,6.70 kg/hm²,18.39 kg/hm² and16.68kg/hm² respectively.It could be seen clearly that cucumber in a large fertilizer planting during the flooding caused NO₃-N leakage higher than that planted during the catch.