The experimental results of soil nutrients in Eucalyptus forest showed that:
(1) Effect of slope on soil nutrient of eucalyptus forest soil The nutrient content of 0-20 cm soil of 2-year-old eucalyptus forest in Daguishan Forest Farm was analyzed. All five indicators, including N, P, K, K, and Mg, represented gentle slope> protected slope> steep slope. Compared with gentle slope, the decline of steep slope was 69.9% and 63 respectively. At the rate of .3%, 81.4%, 64.7%, and 96.3%, the risk declined by 8.8%. 5%, 56. 6%, 37. 0%, 7. 0%, 90. 6%. As the slope increases, the quick-impact P increases gradually and the exchangeable Ca decreases. Compared with the gentle slopes, the increase rates of the quick-impact P on the steep slopes and the dangerous slopes are 268.4% and 700.0%, respectively, and the exchange rate Mg decreases. It reached 77.5% and 96.5% respectively. Among these three slope levels, exchanging Ca reached a very significant level, and full K reached a significant level. It can be seen that the slope has different effects on the accumulation of different nutrient elements in the soil of Eucalyptus plantation.
(2) Effects of algebra and forest age on soil nutrient of eucalyptus forest soil The 0-20 cm soil nutrient of eucalyptus pure forest with different forest ages in the first and second generation forests of Qipo Forest Farm was analyzed. In the first-generation forest, the soil nutrient indexes of the 14-year-old eucalyptus forest were higher than those of the 1-year-old and 4-year-old eucalyptus forests. The contents of total N, available P, and exchangeable Ca increased with the increase of forest age, especially for the 14-year-old eucalyptus forest. Exchangeable Ca is more than three times higher than the one-year-old and four-year-old stands, while all-P, full-K, quick-impact K, and exchangeable Mg are the lowest in four years. In particular, the total K and available K content of the 14-year-old stands are four years old. Stand 5 times and 2 times. It can be seen that the manpower of the eucalyptus plantations was restored after several years of artificial breeding.
In the 2nd generation forest, compared to the 1-year-old eucalyptus forest, the 4-year-old eucalyptus forest had all the N, all P, available P, and exchangeable Ca, except that the contents of the full K and available K increased by 68.6% and 40.8%, respectively. The content of exchangeable Mg, etc. showed a downward trend, with a decrease of 5.7%, 9.9%, 58.9%, 20.2%, and 18.8%. The content of available P decreased significantly with the increase of forest age. From the standpoint of different generations of the same forest age, the contents of total N, available P, exchangeable Ca, and exchangeable Mg of the 1-year-old and 4-year-old forests in the second-generation forest were significantly higher than those in the same forest-aged forest of the first-generation forest. The contents of total P and total P are similar, and tend to be the same, while the changes of total K and available K content are 1 forest> 2 forests in 1 year forest stands, 2 forests> 1 forests in 4 year forest stands. . It can be seen that there is a large amount of nutrients remaining in the second generation Eucalyptus forest land.
(3) Effects of mixed cropping patterns on soil nutrients in the Eucalyptus forest soil The 0-20 cm soil nutrients of different planting models of the eucalyptus algebra and the same forest age in the Qinlian Forest Farm were analyzed, and the contents of total N and available P were highest in the pure forest, followed by For the mixed forest, the compound model of forest and grass was the lowest, which was 79.5% and 146.0% lower than that of pure forest. The contents of total P and hydrolysis N were mixed forest> pure forest> forest and grass compound. Mixed forests increased by 38.3% and 35.3% respectively compared to pure forests; total K, available K, exchangeable Ca, exchangeable Mg content For the forest and grass compound> pure forest> mixed forest, the composite pattern of forest and grass increased by 46.8%, 34.1%, 48.8% and 45.0%, respectively, compared with pure forest.
On the whole, among the three planting patterns, the total N and available P content of the pure Eucalyptus plantation ranks the first place, and the remaining nutrient content ranks the second place; the contents of total P and N of the mixed plantation of the Eucalyptus grandis and the Acacia crassicarpa are ranked first. 1 person, all N and quick-acting P ranks second, Acacia crassifolia has better soil improvement effect; composite management model of fast-born earthworm and forage has the lowest N, N, P, and P all other nutrient contents. Both fast-growing eel and pasture are short-term crops and consume the most for N and P.
(4) Effects of previous cropping tree species on soil nutrient content of Eucalyptus forest soil The 0-20 cm soil nutrient content of different previous cropping plots in Qinling Forestry Farm was analyzed. Except for exchangeable Ca, the nutrient contents in Eucalyptus plantations with eucalyptus as the previous crop were relatively low. Among the fast-growing plantation forests of Cinnamomum camphora, Acacia crassicarpa and Pinus massoniana forest, the content of total P, total K and exchangeable Mg was the lowest, and the total P content decreased by 35.2%, 53.6% and 36.8%, respectively. At 0%, the total K content decreased by 47.6%, 32.3%, and 36.4%, and the exchangeable Mg content decreased by 46.8% and 62.8%. 2% and 44. 6%; Whole N, hydrolyzed N, and quick-acting P contents were 80.9% lower (Pinus massoniana forest), 59.0% (Qing Acacia forest), and 91.1% (Qing Acacia forest) than the highest value of the corresponding element. ; The K content is not very different. The eucalyptus forest area with eucalyptus as the former has the largest exchangeable Ca content, which is more than 6 times that of other forest stands. On the whole, the available nutrients in the Eucalyptus pure forest with Acacia crassicarpa as its predecessor were kept at a high level.
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