【正文】 示在第一、二種作物上產(chǎn)生等量邊際產(chǎn)值所需要的肥料總量?！　uppose that the total amount of potash available is Kconstraint. Of this, an amount K1constraint should be allocated to crop 1, while an amount K2constraint should be allocated to crop 2. Since K1constraint+K2constraint=Kconstraint, all of the fertilizer is used. In addition, since MVP1=MVP2 with this distribution of potash any reallocation of fertilizer between the two crops will result in reduced profits.　　機(jī)會(huì)成本的概念可以用來解決其它有限制的問題。表的上半部分表示在不同N、K肥水平下N和K的邊際產(chǎn)量?！　uppose that nitrogen price/potash price ratio is approximately as presented in Table 2. To see how this ratio is used, suppose there was only enough capital to spend 150 yuan/ha on fertilizer. In this case, the optimal purchase would involve approximately 75 kg/ha of nitrogen and 75 kg/ha of potash. This would generate the maximum possible profits given the constraint on fertilizer expenditures.(表：表2 資金在兩種不同肥料之間的分配 )N (kg/ha) 施氮量 氮鉀邊際產(chǎn)量比 MPPN/MPPK 花費(fèi) Expenditures K2O (kg/ha) K2O (kg/ha) 75 150 225 75 150 225 75 152 207 262 150 250 305 359 225 347 402 457 300 445 500 554 375 542 597 652 注釋：Fertilizer Prices (yuan/kg):rN=。如果購買化肥的資金有限，那應(yīng)該如何分配這筆有限的資金呢？　　As a final example of a constraint, suppose there are two crops, and that each crop responds to a different fertilizer. More specifically, assume that crop 1 responds to nitrogen, while crop 2 responds to potash. If there is a constraint in the amount of yuan that can be spent on fertilizer, how should this limited amount of yuan be allocated?　　假定多一元的資金用于第一種作物需要的N肥上，而不是第二種作物需要的K肥上，那就可以多購買1/rN公斤N肥，多生產(chǎn)MPP1/rN公斤的第一種作物，這是多用一元錢在N肥上所產(chǎn)生的邊際收益?！　quating the opportunity cost to the marginal benefit gives the expression for maximizing profits. That is, profits will be maximized when　　P1MPPN/rN=P2MPPK/rK　　圖4表示了如何應(yīng)用這一原則來決定資金在用于兩種作物的兩種肥料之間的分配?！　igure 5 shows the first panel in more detail. For instance, if a quantity XN of fertilizer is required to produce a marginal value product of MVPN, then with a price of nitrogen of rN, the expenditure required to produce marginal value product MVPN will be rNXN.(圖：圖5 邊際價(jià)值產(chǎn)品（MVP）與肥料費(fèi)用之間關(guān)系的確定)　　圖4的第三幅圖表示，在兩種作物中產(chǎn)生相同水平的邊際產(chǎn)值需要投在化肥上的總資金，其曲線為第一、二圖曲線的水平相加。在低產(chǎn)區(qū)44名被采訪的農(nóng)民中，25名沒使用K肥，這可以說明這個(gè)地區(qū)有相當(dāng)一部分農(nóng)民得不到鉀肥?！　 shortage of potash at the farm level can result from any number of different constraints that are present elsewhere in the fertilizer system. In the remainder of this lecture, I would like to identify some of these constraints. I would then like to examine how fertilizer should be optimally distributed given that the constraints are in place. In this examination, the concept of opportunity cost will play an important role.　　限制肥料供應(yīng)的因素之一，是肥料生產(chǎn)、分銷和裝卸系統(tǒng)方面的限制。如果鉀肥和水稻的價(jià)格都是固定的，產(chǎn)量增加的總結(jié)果是該地區(qū)的利潤增加。由于總供應(yīng)量是固定的，分給一個(gè)地區(qū)較多的鉀肥，意味著其它地區(qū)只能分到較少的鉀肥?！　o determine the optimal allocation of fertilizer in this situation, it is necessary to know the relative size of the MPP of potash in all regions. For illustration purposes, however, I will limit my parisons to the high yield region. It should be noted that since the MPPs have been calculated at the level of average use for all farmers, the analysis assumes that within each region, fertilizer has been reallocated so that all farmers have access to fertilizer.　　由于低產(chǎn)區(qū)鉀肥邊際產(chǎn)量大于零，高產(chǎn)區(qū)鉀肥邊際產(chǎn)量等于零，從高產(chǎn)區(qū)把鉀肥重新分配到低產(chǎn)區(qū)，會(huì)使兩類地區(qū)的總利潤增加。常用的是平均產(chǎn)量，平均產(chǎn)量高的地區(qū)得到較多的化肥。如果某個(gè)地區(qū)很肥沃，又或許由于肥料運(yùn)作系統(tǒng)中存在一些限制因素而化肥用量不大，那就會(huì)出現(xiàn)這種情況?！　he discussion above assumes the amount of the various fertilizers is fixed and that all that could be done is to reallocate the fertilizer among different farmers or among different regions. While this may be true in the short term, over the longer term, a redistribution of the fertilizer budget among different fertilizers may be possible.　　如果是這樣，從購買N肥和P肥的資金中抽出一部分來購買K肥，利潤就可能會(huì)增加?！　f this is the case, profits could be increased by taking some of the budget used for the purchase of nitrogen and phosphate and using it to purchase additional potash. This follows because it was determined that both nitrogen (at least in the high yield region) and phosphate are being overused relative to the level that would maximize profits. Thus, a reduction in the use of these fertilizers would, by itself, increase profits. Allocating the yuan spent on nitrogen and phosphate to potash would result in yet another increase in profits.　　因?yàn)樯侠械追视昧窟^高，所以考慮的解決方案相對(duì)比較簡單?！　his means that data on the prices of the outputs and the prices of the fertilizers, as well as the marginal physical product of fertilizer on each of the different crops is required to make an assessment of how fertilizer should be allocated.　　從長遠(yuǎn)看，如果經(jīng)費(fèi)不受限制，應(yīng)該考慮不同肥料在不同作物間的分配，即考慮達(dá)到最高利潤的肥料用量。比如，在上述例子中，增施鉀肥可能會(huì)增加氮肥和磷肥的邊際產(chǎn)值，因而氮肥和磷肥的用量也需要提高。 that is, to consider the question of what is the quantity of fertilizer that maximizes profits. The rules for determining optimal fertilizer allocation were outlined in Economics of Fertilizer I. Recall from that lecture that the optimal allocation of fertilizer involves balancing the different fertilizers so the price of each fertilizer equals the marginal value product of that fertilizer. Since the quantity of any one fertilizer influences the marginal value product of the other fertilizers, the optimal quantity of a particular fertilizer connot be chosen independently of the other fertilizers. Thus, for instance, in the example above, it may be the case that increased use of potash will increase the marginal value products of nitrogen and phosphate, thereby requiring an increase in their use as well. Similarly, provision of a deficient nutrient like sulphur may raise the marginal products of nitrogen, phosphate, and potash, thus requiring increased levels of these nutrients. The exact balance among the fertilizers depends on a full knowledge of the nature of the production function.　　本講座要強(qiáng)調(diào)的觀點(diǎn)是：無論供應(yīng)充足與否，合理分配肥料資金需要知道不同肥料對(duì)增產(chǎn)的作用、各種肥料在決定產(chǎn)量時(shí)的相互作用以及產(chǎn)品和肥料的