On July 31, 1790, U.S. President George Washington signed the country's first ever patent. It was given to Samuel Hopkins of Pittsford, Vt., for an improvement 'in the making of Pot ash and Pearl ash by a new Apparatus and Process.'

Back then, potash was derived from the ashes of hardwood trees and other plants, and mainly used to make soap, glass and saltpeter for gunpowder. The mineral became one of America's biggest exports and a linchpin of its early economy.

Today, the humblecrystal, which is often pink in color, is mainly used to make fertilizer. As such, it plays an even bigger role: Helping to feed the world's expanding masses.

'We need more food for a growing population, so the demand for potash will keep increasing,' says Terry Roberts, president of the International Plant Nutrition Institute, a research group in Norcross, Ga.

Potash is the common name given to various compounds that contain potassium. Along with nitrogen and phosphorus, potassium is one of three primary nutrients needed by plants.

Potassium ions help activate some 80 enzymes in plants, enabling them to fight disease, survive winters, carry out photosynthesis and, thus, improve crop yields. Without potassium, crops can't reproduce and make grains, vegetables or fruit.

Humans can't survive without potassium, either. It helps to synthesize proteins, build our muscles, and maintain the normalelectrical activity of the heart. Good food sources of the mineral include milk, meat, fruits and vegetables.

But the natural stores of potassium are declining in many crop-growing regions of the world. In America's corn belt, for example, years of rain and harvests have gradually reduced the quantity of mineral in the soil. Some countries with the greatest food needs -- China, India, Brazil -- have soils that are naturally low in potassium.

Hence the big demand for potash. As the growing population requires more protein, more feed crops have to be grown -- which requires a larger supply of potash.

The good news: There's plenty of the stuff in the ground.

While potassium is present in most rocks and soils, the ore is often mined from ancient sea beds and salt lakes.

'The current 8.3 billion tons of known global reserves will last for about 250 years at current rates of production,' says Dr. Roberts of IPNI.

Geologists say that the existence of other, untapped deposits probably means that the world won't run out of potash for thousands of years.

Gautam Naik

• patent [´peitənt, ´pæ-] a.专利的 n.专利品 (初中英语单词)
• improvement [im´pru:vmənt] n.改进，改善，进步 (初中英语单词)
• mainly [´meinli] ad.主要地；大体上 (初中英语单词)
• mineral [´minərəl] n.矿物 a.矿物的 (初中英语单词)
• humble [´hʌmbəl] a.谦卑的 vt.贬抑 (初中英语单词)
• crystal [´kristəl] n.水晶 a.水晶的 (初中英语单词)
• international [,intə´næʃənəl] a.国际的，世界的 (初中英语单词)
• institute [´institju:t] n.学院 vt.建立；设置 (初中英语单词)
• research [ri´sə:tʃ] n.&vi.调查；探究；研究 (初中英语单词)
• contain [kən´tein] v.包含；容纳；抑制 (初中英语单词)
• primary [´praiməri] a.主要的 n.居首位的 (初中英语单词)
• survive [sə´vaiv] vt.幸存；残存 (初中英语单词)
• maintain [mein´tein] vt.维持；保持；继续 (初中英语单词)
• normal [´nɔ:məl] a.正规的 n.正常状态 (初中英语单词)
• existence [ig´zistəns] n.存在；生存；生活 (初中英语单词)
• apparatus [,æpə´reitəs] n.仪器；装置 (高中英语单词)
• nitrogen [´naitrədʒən] n.氮 (高中英语单词)
• reproduce [,ri:prə´dju:s] v.繁殖；复制；翻版 (高中英语单词)
• electrical [i´lektrikəl] a.用电的；与电有关的 (高中英语单词)
• brazil [brə´zil] n.巴西 (高中英语单词)
• billion [´biljən] num.万亿 (高中英语单词)
• fertilizer [´fə:tilaizə] n.肥料 (英语四级单词)
• gunpowder [´gʌn,paudə] n.火药 (英语六级单词)
• nutrition [nju:´triʃən] n.营养(物)；食物 (英语六级单词)
• protein [´prəuti:n] n.蛋白质 a.蛋白质的 (英语六级单词)