| In recent years, it has become increasingly widespread in the Northeast and North China that only base organic manure is applied in winter wheat-summer maize rotation without fertilizer topdressing. This fertilization measurement is usually used by farmers who raise livestock and poultry or could get cheap animal manure. In this fertilization system, worker costs for topdressing fertilization will be reduced. However, few studies were done on behavior and fate of nitrogen, especially on nitrogen efficiency and its impacts on environment by one base organic manure application in winter wheat-summer maize rotation.In order to elucidate nitrogen fate and efficiency of organic manure, four field experiments were carried out from September 2007 to October 2008, respectively in Lingxian (Shandong province), Yangxinzhuang and Shijiatun (Jixian County of Tjanjin City). These experiments were mainly used to research nitrogen use efficiency and crop yield. Besides this, experiment in Lingxian was used to research the uptake of manure nitrogen by crop, its transformation and distribution in soil environment. 15N tracer technique was adapted in this experiment, and some micro-plots and field plots were carried out too. 15N marked organic manure and chemical fertilizers were applied to these micro-plots. The main conclusions are as follows:1 ) The experimental site of east Yangxinzhuang is of higher fertility (higher yield). In the 300-N-treatments (applying 300 kg N·hm-2 nitrogen to wheat-maize rotation), there was no significant difference between crop yields of 1-OM (applying base organic manure in winter wheat-summer maize rotation without fertilizer topdressing) and 5-CF (applying chemical fertilizer for five times in winter wheat-summer maize rotation, and three times for winter wheat, twice for summer maize) fertilization measurement. Their yields (wheat plus maize) were respectively 18034 and 18101 kg·hm-2. After winter wheat and summer maize harvest, there was also no significant difference between the two kinds of fertilization measurements in 0-20cm soil NO3-N content. Their content were respectively 13.2 and 11.3 mg·kg-1 after winter wheat harvest, were respectively 7.2 and 7.8 mg·kg-1 after summer maize harvest. The experimental site of Lingxian (Shandong Province) is of lower fertility (lower yield). In the 300-N treatments, the total yield of 5- CF is significant high from that of 1-OM. Their yields (wheat plus maize) were respectively 12503 and 10782 kg·hm-2. After winter wheat harvest, the 0-20cm soil NO3-N content of 5-CF was not significantly different from that of 1-OM. After summer-maize harvest, the 0-20cm soil NO3-N content of 1-OM was 7.2 mg·kg-1, which was significant high from that of 5- CF (4.6 mg·kg-1).2)The 15N tracer studies have shown: In the periods of winter wheat– summer maize rotation, there was no significant yields difference between 450-N treatment (applying 450 kg N·hm-2 nitrogen to wheat-maize rotation) and 300-N treatment of 1-OM fertilization measurement. Their yields were respectively 11807 and 10782 kg·hm-2. The Nlost-dff (Nitrogen lost derived from fertilizer) of 450-N treatment was significantly increased to 153 kg N·hm-2, and the 300-N treatment was only of 55 kg N·hm-2. The NUE (Nitrogen use efficiency) of 450-N treatment was 13%, which was significantly lower than that of 300-N treatment (17%). The NSoil-dff (the soil nitrogen remaining derived from fertilizer) of 450-N treatment was 238 kg N·hm-2, which was significantly higher than that of 300-N treatment (172 kg N·hm-2). The Nmin-dff (the soil mineral nitrogen remaining derived from fertilizer) of 450-N treatment was 3.7 kg N·hm-2, which was no significantly difference from that of 300-N treatment (3.1 kg N·hm-2). These results have shown that 450-N treatment is application 150kg nitrogen fertilizer more than 300-N treatment, two third of them are lost, and one third of them remain in soil.In the 300-N treatment of 1-OM fertilization measurement, after winter wheat harvest, Nuptake (nitrogen absorption by the crop), NSoil-dff, Nlost-dff and Nmin-dff were respectively 26, 219, 55, 2.4 kg N·hm-2; NUE and Nlost-dff-coef (lost coefficient of Nitrogen derived from fertilizer) were respectively 9% and 18%. After summer maize harvest, Nuptake, NSoil-dff, Nlost-dff and Nmin-dff were respectively 26, 172, 21 and 3.1 kg N·hm-2; NUE and Nlost-dff-coef were respectively 9% and 7%.In the 450-N treatment of 1-OM fertilization measurement, after winter wheat harvest, Nuptake, NSoil-dff, Nlost-dff and Nmin-dff were respectively 30, 307, 113 and 3.7 kg N·hm-2; NUE and Nlost-dff-coef were respectively 7% and 25%. After summer maize harvest, Nuptake, NSoil-dff, Nlost-dff and Nmin-dff were respectively 29, 238, 39 and 3.7 kg N·hm-2; NUE and Nlost-dff-coef were respectively 7% and 9%.3)The 15N tracer studies have also shown: In the lower fertility conditions, the crop yield of 5-CF was significantly higher than that of 1-OM. After a rotation period, in 300-N treatments, soil 0-20cm Nmin-dff and 0-200cm Nmin-dff of 5-CF were respectively 7.6 and 8.7 kg N·hm-2, which were significantly higher than those of 1-OM (2.6 and 3.1 kg N·hm-2). Also, in 450-N treatments, soil 0-20cm Nmin-dff and 0-200cm Nmin-dff of 5 -CF are respectively 11.0 and 15.2 kg N·hm-2, which were significantly higher than those of 1-OM (3.0 and 3.7 kg N·hm-2) too.4)Experimental results of different varieties of organic manure showed that: In winter wheat-summer maize rotation, crop yields of 300-N had no significant difference among the treatments of applying cow dung, pig manure and duck manure. Their total (wheat plus maize) yields of different manure treatments were respectively 14961, 15459 and 15231 kg·hm-2. Their NUE (wheat plus maize) were respectively 18%, 18% and 23%, also had no significant differences. After winter wheat harvest, 0-20cm soil NO3-N content of duck manure application treatment (19.1 mg·kg-1) was significantly higher than that of cow dung application treatment (9.8 mg·kg-1) and pig manure application treatment (13.3mg·kg-1). After summer maize harvest, 0-20cm soil NO3-N content of duck manure application treatment (12.8 mg·kg-1) was significantly higher than that of cow dung application treatment 6.8 mg·kg-1) and pig manure application treatment (7.5mg·kg-1) too. These results have shown that different varieties of organic fertilizers have significant differences in nitrogen mineralization in soil.These studies are preliminary show that in the North China Plain of high fertility soil, crop yields are basically the same between 1-OM and 5- CF fertilization measurement in winter wheat– summer maize rotation. After summer maize harvest, soil 0-20cm NO3-N content is significant low, and the risk of farmland leaching or run-off is low too. Considering worker costs for topdressing fertilization will be reduced, 1-OM fertilization measurement is worthy to be recommended in the North China Plain of high fertility soil. |
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