第一章 耕者的黄昏：传统农业的系统性困境 / Chapter 1: Twilight of the Plow: Systemic Dilemmas of Conventional Agriculture

2022年，肯尼亚西部基苏木郡的干燥风裹着赤红的沙尘，刮得人脸上生疼。62岁的卡曼加蹲在龟裂的玉米地埂上，指尖捻起一撮干得发脆的土壤，用力一捏就碎成粉末——这是他种了30年地以来，头一回见玉米还没抽穗就枯死在田里。往年这个时候，这片3亩的玉米地至少能收800公斤玉米，够全家六口人吃半年，还能卖200公斤换医药费、供三个孙子上学。可2022年的降雨量只有往年的三成，地里连杂草都长不出来，三个孙子因为营养不良先后住进了县医院，他卖了两头养了3年的山羊才凑够2万肯尼亚先令（约160美元）的医药费，还欠了信用社5000先令的化肥贷款。信用社的人说，要是今年还不上钱，就要收回这片地——那是卡曼加一家唯一的生计所在。

In 2022, the dry wind of Kisumu County in western Kenya wrapped around the red sand and dust, stinging people's faces. Kamanga, 62, squatted on the cracked ridge of the cornfield, pinched a pinch of dry and brittle soil with his fingertips, and crushed it into powder with a hard pinch - this was the first time he had seen corn wither in the field before tasseling since he started farming 30 years ago. At this time last year, this 3-acre cornfield could harvest at least 800 kilograms of corn, enough for the whole family of six to eat for half a year, and sell 200 kilograms to pay for medical expenses and support three grandchildren to go to school. But in 2022, the rainfall was only 30% of that in previous years, and even weeds could not grow in the field. Three grandchildren were hospitalized for malnutrition one after another. He sold two goats that he had raised for 3 years to raise 20,000 Kenyan shillings (about $160) for medical expenses, and still owed 5,000 shillings for fertilizer loans from the credit union. The credit union staff said that if he could not pay back the money this year, they would take back the land - that was the only livelihood of Kamanga's family.

9000公里外，美国爱荷华州迪莫伊市的54岁农场主汤姆正盯着化肥价格单发愁。他继承了父亲留下的500英亩玉米和大豆田，每年要施用110吨氮肥、30吨磷肥和20种农药，2022年俄乌战争爆发后，化肥价格直接翻了一倍，他的投入成本比2021年涨了40%，全年净利润只有往年的20%。更让他愧疚的是，每年春天融雪时，约有30%的氮磷肥料会随融水流入密西西比河，最终在墨西哥湾形成面积超过1.6万平方公里的“死亡区”——相当于整个北京市的面积，每年给美国渔业带来超过2亿美元的损失。可如果不施化肥，玉米和大豆的单产会直接下降30%，他连贷款都还不上。“我父亲种了一辈子地，我也种了30年，从来没见过这么难的年头，”汤姆在农场日志里写道，“要么接着用化肥，要么破产，没有别的选。”

9000 miles away, 54-year-old farmer Tom in Des Moia, Iowa, was staring at the fertilizer price list and worrying. He inherited 500 acres of corn and soybean fields from his father, and every year he applies 110 tons of nitrogen fertilizer, 30 tons of phosphate fertilizer and 20 kinds of pesticides. After the outbreak of the Russia-Ukraine War in 2022, the price of fertilizer directly doubled, and his input costs increased by 40% compared with 2021, with only 20% of the net profit of previous years for the whole year. What made him feel more guilty was that every spring when snow melts, about 30% of the nitrogen and phosphorus fertilizer will flow into the Mississippi River with the meltwater, and eventually form a "dead zone" with an area of more than 16,000 square kilometers in the Gulf of Mexico - equivalent to the area of the whole Beijing, bringing more than $200 million in losses to the US fishing industry every year. But if he does not apply fertilizer, the yield of corn and soybeans will directly drop by 30

可汤姆的困境远不止化肥涨价这么简单。2022年秋天收获时，他统计了全年农场的投入产出：化肥农药成本占到了总投入的42%，比2019年的28%高出了14个百分点，而净利润率只有3.2%，是过去20年来的最低值。更让他难以接受的是，他每年施用的110吨氮肥中，有33吨会随融雪和降雨流入密西西比河流域，下游的密苏里州渔民抱怨说，近10年来密西西比河的鱼类数量下降了40%，其中70%的死亡与氮磷污染导致的缺氧有关[^1]。爱荷华州农业部的统计显示，2022年该州有12%的中小农场主因为化肥成本上涨濒临破产，其中8%的农场已经在出售土地的边缘。

But Tom's dilemma goes far beyond the rising price of fertilizers. When he harvested in the fall of 2022, he calculated the input-output of his farm for the whole year: the cost of fertilizers and pesticides accounted for 42% of the total input, 14 percentage points higher than the 28% in 2019, and the net profit margin was only 3.2%, the lowest in the past 20 years. What made him even more unacceptable was that of the 110 tons of nitrogen fertilizer he applied every year, 33 tons would flow into the Mississippi River basin with snowmelt and rainfall. Fishermen in downstream Missouri complained that the number of fish in the Mississippi River had decreased by 40% in the past 10 years, 70% of which were related to hypoxia caused by nitrogen and phosphorus pollution[^1]. Statistics from the Iowa Department of Agriculture show that in 2022, 12% of small and medium-sized farmers in the state were on the brink of bankruptcy due to rising fertilizer costs, and 8% of the farms were on the edge of selling their land.

就在汤姆为化肥发愁的同一时间，在湄公河三角洲越南薄寮省的52岁稻农黎氏芳正站在被淹的水稻田里发呆。2023年3月的春汛比往年提前了20天，她家5公顷刚插完10天的水稻苗全被淹在了20厘米深的浑水里。这还不是最坏的情况——过去10年里，海平面上升导致的海水倒灌已经让这片土地的土壤pH值从6.5降到了4.8，相当于变成了强酸性土壤，水稻单产从2013年的每公顷6.2吨降到了2023年的3.4吨，几乎腰斩。更麻烦的是，盐碱化的土壤需要施更多的石灰来中和酸性，每年光是买石灰的钱就要花掉2000万越南盾（约850美元），占她全年种稻收入的15%。“我父亲种了一辈子稻，我种了20年，从来没遇到过这么难的情况，”黎氏芳用袖子擦了擦脸上的泥水，指了指远处已经被淹的村舍，“要是今年再歉收，信用社就要收回这块地，我们全家就只能去胡志明市打工了。”

At the same time that Tom was worrying about fertilizers, 52-year-old rice farmer Le Thi Phuong in Ben Tre Province, Vietnam, in the Mekong Delta was standing in the flooded rice field in a daze. The spring flood in March 2023 came 20 days earlier than in previous years, and all the rice seedlings that had just been transplanted for 10 days on her 5-hectare field were submerged in 20 cm of turbid water. This is not the worst case - over the past 10 years, seawater intrusion caused by sea level rise has reduced the soil pH of this land from 6.5 to 4.8, which is equivalent to strong acid soil, and the rice yield per hectare has dropped from 6.2 tons in 2013 to 3.4 tons in 2023, almost halved. What is more troublesome is that salinized soil needs to apply more lime to neutralize the acidity. The money for buying lime every year is 20 million Vietnamese dong (about $850), accounting for 15% of her annual rice income. "My father has been growing rice all his life, and I have been growing it for 20 years. I have never encountered such a difficult situation," Le Thi Phuong wiped the mud off her face with her sleeve and pointed to the nearby flooded village. "If we have another poor harvest this year, the credit union will take back this land, and our whole family will have to go to Ho Chi Minh City to work."

<section id="land-degradation">

一、土地退化：被透支的土壤生命线

Land Degradation: The Overdrawn Lifeline of Soil

三个看似毫无关联的案例，指向了同一个核心事实：传统农业的生产模式已经走到了系统性的崩溃边缘。联合国粮农组织（FAO）2023年发布的《粮食及农业状况》报告显示，全球33%的土壤已经出现中度到重度退化，每年有240亿吨肥沃土壤因风蚀、水蚀和过度耕种而流失，相当于每年损失3400万吨氮肥、1000万吨磷肥的价值，每年造成的直接经济损失高达4700亿美元[^3]。

The three seemingly unrelated cases point to the same core fact: the production model of conventional agriculture has reached the edge of systematic collapse. The 2023 *State of Food and Agriculture* report released by the Food and Agriculture Organization of the United Nations (FAO) shows that 33% of the world's soils have already suffered from moderate to severe degradation. Every year, 24 billion tons of fertile soil are lost due to wind erosion, water erosion and over-cultivation, which is equivalent to a loss of 34 million tons of nitrogen fertilizer and 10 million tons of phosphate fertilizer every year, with a direct economic loss of up to $470 billion annually[^3].

在撒哈拉以南非洲，土地退化已经直接威胁到2亿多小农户的生计。卡曼加家的3亩玉米地，土壤有机质含量已经从1990年的3.2%降到了2023年的1.1%，远低于维持作物正常生长的2%临界值。当地农业推广站的检测报告显示，这片土地的氮含量只有正常水平的40%，磷含量只有35%，每年需要投入至少15000肯尼亚先令（约120美元）的化肥才能维持300公斤/亩的单产，但卡曼加去年连买化肥的钱都凑不齐。FAO的统计显示，撒哈拉以南非洲的土地退化速度是全球平均水平的2倍，每年每公顷土地的生产力下降10-15%，预计到2030年，该地区的玉米单产将再下降25%，届时将有3000万人面临严重的粮食短缺。

In sub-Saharan Africa, land degradation has directly threatened the livelihoods of more than 200 million smallholders. The soil organic matter content of Kamanga's 3-acre cornfield has dropped from 3.2% in 1990 to 1.1% in 2023, far below the 2% critical value required to maintain normal crop growth. The test report from the local agricultural extension station shows that the nitrogen content of this land is only 40% of the normal level, and the phosphorus content is only 35%. At least 15,000 Kenyan shillings (about $120) of fertilizer needs to be invested every year to maintain a yield of 300 kg per mu (about 0.067 hectares). But Kamanga could not even raise the money to buy fertilizer last year. FAO statistics show that the land degradation rate in sub-Saharan Africa is twice the global average, with the productivity of each hectare of land decreasing by