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对豆类作物推荐施种肥是因为我们知道在出现生物固氮之前豆科植株对矿质氮有生理依赖。然而，在对农民进行施氮肥推荐时，通常不能考虑土壤有效氮对作物早期生长对矿质氮的实际需要。在大多数情况下，上季作物残留的氮加上由有机物分解的矿质氮就足够豆类作物早期生长的需要。7 V1 n, _$ P# _- I
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Recommendations for starter N originate from our knowledge of the legume’s physiological dependence on mineral N prior to onset of BNF. Starter N recommendations to farmers, however, usually fail to account for soil available N relative to the crop’s actual requirement for mineral N during early growth. Most often, residual N from previous crops plus mineralized N from organic matter are sufficient to meet the early N requirements of legumes.
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% c/ k6 S' [% i 在各种土壤类型和气候条件的大面积上遵循施氮推荐在生物学和经济学上的潜在费用是巨大的。例如，1994年估计有538,165吨氮肥施在了中国17 个省的1050万公顷的大豆及花生上（钾磷研究所，Sam Portch私人通信），仅这一氮管理措施的直接投入费用就高达26.32亿元人民币。生物固氮潜力捕获的氮减少了215000吨以上?-假设氮肥利用率为40%，如果对豆类作物生物固氮管理得当的话，只以小部分氮肥成本就可获得这些氮。
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% Q" R" L- v1 |1 V* G+ q- C The potential biological and economic costs of following recommendations for starter N across large areas with variable soil types and climates are enormous. For example, in 1994 it was estimated 538,165 metric tonnes (mt) of N were applied to 10.5 million ha of soybean and groundnut crops across 17 provinces of China (Potash & amp; amp; Phosphate Institute, Sam Portch personal communication). Direct input cost alone of this N-management option could be as high as 2,632 million RMB ($317 million U.S.). Reduction in potential capture of N from the BNF process could exceed 215,000 mt - assuming an FUE for N of 40%. This N could be obtained at a small fraction of the cost of N fertilizer by properly managing legume BNF.
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氮的生物学反应与其成本之比和将这些财力资源用于其他管理选择的预期经济收益决定着施氮肥是否作为一种推荐管理措施。本文在生物学及生态学方面评述豆类作物的氮肥管理，并进一步评估了在中国对豆类作物的氮肥管理选择的经济费用和收益，包括施用氮肥和非氮肥投入的机会成本。0 _8 y( \: d3 o; y- h t
1 I% e7 n3 u( _2 y. t Whether N fertilizer should be a recommended management practice is determined by biological response to N relative to its costs and the foregone economic benefit from using these financial resources for other management options. This paper reviews the biological and ecological aspects of N-management of legumes. Further, it evaluates the economic costs and benefits of N-management options for legumes in China including opportunity costs of N fertilizer use in relation to non-N fertilizer inputs.
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2. 豆类作物对氮的需要和吸收?Nitrogen Requirements and Uptake by Legumes
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; Q) G3 M) ]9 _* ~) e; O4 g 2.1 豆类作物在农业上的重要性 Importance of legumes in agriculture1 w3 j0 ^7 p5 e# S/ |) R
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籽用豆类是世界农业中第二重要的作物。通过直接食用和转化为动物产品，它们是重要的食物蛋白的来源。在许多发展中国家豆类蛋白占蛋白质消耗的大部分；在一些发达国家及那些经济快速增长较不发达国家，对豆类蛋白需求的增长速度超过了对谷物需要的增长。收入的增加加速对动物蛋白与豆类作物这种动物原料的需求。在很多情况下，豆类作物生产的增加反映了畜牧生产的变化。例如，在1980~1992年间，中国畜牧业迅速增长，在同一时期，大豆及花生生产也提高了，豆类作物生产的增加几乎完全是来自管理措施的改进。改进作物管理与产量潜力的一个标志是磷肥与钾肥的施用量的急剧增加。本文将说明管理的改进与豆类作物高产是农民从生物固氮中获得最大利益的条件。" r! I0 A9 H* |& d
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Grain legumes are the second most important crop in world agriculture. They are an important source of dietary protein through direct consumption and conversion to animal products. In many developing countries legume protein accounts for a major portion of protein consumption. In developed countries and in those lesser developed countries that are experiencing rapid economic growth, demand for legume protein is accelerating faster than demand for cereals. Rising incomes accelerate demand for animal protein and legume crops, the raw materials for animal industries. In many cases increased legume production mirrors changes in animal production. For example, animal production in China increased rapidly between 1980 and 1992 In the same period soybean and groundnut production also rose. Increased legume production was almost entirely due to higher yields from improved management. One indicator of improved crop management and yield potential is the dramatic increase in P and K fertilizer consumption in China. This paper will show improved management and higher yields of legume crops are precisely the conditions where farmers can gain the largest benefit from legume BNF.
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2.2 豆科作物吸收的总氮量 Total nitrogen assimilation by legumes
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( u$ N; V+ H9 m3 n 大多数豆类作物的产量及总生物量低于谷类作物，但豆类种子及叶片中的蛋白质含量却高几倍。蛋白质本质上就是带有氨基的碳链。豆类作物组织高浓度的蛋白质就意味着对氮素同化的高度需求。( K$ X: }! x/ f/ ^( o# V, G
3 ]: C1 o( i+ r While total biomass and yield of most legume crops is lower than cereals, legume seed and leaf protein concentrations can be several times higher. Since proteins are essentially carbon chains with attached amino groups, the high concentration of protein in legume tissues translates into a high demand for nitrogen assimilation.
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, g/ r; Q$ _ g& n) u% G2 w2 y 豆类作物的产量与大多数粮食作物一样是同生长过程中氮的同化量密切相关的（Gassman etal, 1993, Herridge et al, 1984），即使要达到中等产量，豆类作物同化的氮量比谷类要多。豆类作物对氮素的高需要与其可同化来源于大气及无机氮的事实，使研究的焦点趋于提高氮的同化量以增加豆科作物产量。, L0 G0 u2 ]& V
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Yield of legumes, as with most food crops, is linked to the amount of N assimilated during crop growth (Cassman et al., 1993, Herridge et al., 1984). To meet even moderate yield potentials, legumes must assimilate more N than cereals. Both the high N requirements of legumes and the fact that legumes can assimilate N from both atmospheric and mineral sources has tended to focus research toward increasing N assimilation as a way to raise legume yields.7 D4 ?) O+ y. x. R3 Q$ T6 X2 Q
( O6 C B& b% J! Z 表1给出了几种豆类与谷类作物同化氮的全球估计值。全球籽用豆类的产量不足谷类的10%，但豆类同化氮量占谷类的37%。别看大豆平均产量只有1919公斤/公顷，而谷有3000公斤/公顷，但单位面积豆类积累氮的总量却是谷类的2倍。
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Estimates of the global amount of N assimilated by several grain legume and cereal species are given (Table 1) Global grain legume production is less than 10% of cereal production, yet grain legume N assimilation is 37% of the total N accumulated by cereal crops. Despite world average soybean yields of only 1919 kg ha-1 compared to more than 3000 kg ha-1 for most cereal crops, soybean crops accumulate more than twice the N per unit area as cereals. |
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发表于 2009-8-20 17:34
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