巴基斯坦高产作物生产技术发展综述


M. Tahir Saleem* P. R. Hobbs** M. Shadf Zia***
国家肥料发展中心，计划发展部项目主任。伊斯兰堡* CIMMYT地区农学家，尼泊尔** 巴基斯坦农业研究中心，土地和水分部主任。伊斯兰堡***


　　原文摘要 ABSTRACT

　　为满足增长人口的需求，在今后的十年中，巴基斯坦农业必须每年至少增加4%的粮食生产。最高产量研究有助于辨别限制高产的重要因素。然而今后的最高产量研究必须更注重在整体上而不是局限在某种商品作物上提高产量。本文利用一些试验站和先进农民的产量实例与全国平均产量加以比较。目前巴基斯坦全国平均产量只及最高产量的1/4。作物的限产因素已经查明，通常是落后的作物管理限制了高产。强调了在水稻-小麦和棉花-小麦轮作中实行免耕、巴基斯坦雨养农业地区实行深耕、高效利用化肥、合理密植、病虫害防治、除草等一些重要作物管理措施的作用，表明这些措施可以提高巴基斯坦种植制度的有效性和生产力。最后提出建议：巴基斯坦应利用综合植物养分供应概念对国家重要种植制度进行最高产量研究（MYR）的系统研究，以长期保护土壤肥力，使之具有持续生产能力。还建议PPIC可以在巴基斯坦发起最高产量研究，因为这会有助于鉴别限制作物高产的因素，并发展出在全国水平上增产的适当战略。

　　Pakistan agriculture must increase food production by at least 4 per cent per annum in the next decade to meet the demand of the growing population. Maximum yield research helps to identify factors essential for high yield. However, future maximum yield research must look more at increasing yields for a pattern rather than just a single commodity. This paper uses some examples of high crop yields obtained at experimental stations and progressive farmers' fields versus national average yields. National yields are only about one-fourth of the maximum yields obtained in Pakistan. Crop yield constraints have been identified. It is generally the poor crop husbandry which limits high yields. The role of some important crop management practices such as zero tillage in the rice-wheat and cotton-wheat patterns, deep tillage in the rainfed patterns of Pakistan, efficient use of fertilizer, plant density, pest management, weed control, etc. is highlighted to show how they can raise the efficiency and productivity of cropping systems in Pakistan. Finally it is proposed that systematic work be undertaken in Pakistan on maximum yield research (MYR) for important cropping system of the country employing integrated plant nutrient supply concept in order to preserve soil fertility for the long term for sustainable productivity. It is recommended that PPIC may sponsor MYR in Pakistan as it will help identify factors limiting high crop yield and evolve appropriate strategy for increasing yields at national level.

　　1.引言 INTRODUCTION

　　1992年巴基斯坦人口为1.18亿，年增长率超过3.1%，到2000年粮食需求将大大增加，为满足届时l.5亿人口的需要小麦产量需由目前的1470万吨增加到2200万吨，这就是说小麦生产必须增加50%，即年增长5.0%，而不是截止1991~92年度过去十年2.5%的实际增长率（粮食增长仅为1.8%）。换言之，截止至1990年的过去十年增加人口2650万，小麦生产增加了280万吨，但到2000年的下一个十年人口将增加3600万，需要增加小麦790万吨。这是异常艰巨而复杂的任务，必须为最好地利用有限的研究资源找出一条提高农业生产效率和生产力的途径。今后，最高产量研究必须更分散、针对各地特定问题、并更加重视关键农业限制因素。

　　Pakistan has a population of about 118.0 million in 1992 and, at a growth rate of over 3.1% per annum, food requirements by the year 2000 AD will grow enormously; wheat production will have to be increased from the present level of 14.7 million tonnes to 22.0 million tonnes to meet the requirements of almost 150 million population. This means that wheat production should increase by about 50% or an annual growth rate of 5.0% against actual 2.5% for the 10-year period ending 1991-92 (the growth rate for food grains was only 1.8%). In other words, the addition to population for the 10 years ending 1990 was 26.5 million and wheat production increased by 2.8 million tonnes. However, for the next 10 years ending 2000 an additional population of 36.0 million would necessitate an increase of 7.9 million tonnes to meet the requirements. This is a very complex and challenging task that must make optimal use of limited research resources to find ways of increasing the efficiency and productivity of farming. The research will have to be more decentralized, more site specific to address local problems and more focussed on key farmer constraints.

　　努力提高产量的目的是以多学科系统研究弄清各变量及其交互作用为农民提供配套技术夺取高产。因此最高产量研究在帮助研究者达此目的方面大有作用。PPIC发起的前几次会议的效果是重视了这种研究的效益（Dev和Sander，1989；PPIC，1990）。

　　The purpose of striving for maximum yield is to identify variables and their interactions in a multidisciplinary system with a view to packaging information for farmers for obtaining high yields. Thus maximum yield research can play an important role in helping researchers achieve the above goal. Results from previous symposia organized by the PPIC have highlighted the benefits of this type of research (Dev and Sanders, 1989; PPIC, 1990).

　　进一步扩大耕地面积的可能性不大，因此，发展农业生产满足增长人口的需要的唯一源泉是提高单位面积产量。最高产量的系统研究在巴基斯坦尚待进行。然而有一些表明巴基斯坦高产技术概况的有用资料。本文努力简述巴基斯坦获得作物高产的经验和确认最高作物产量的限制因子。

　　Further expansion in cropped area being limited, the only recourse left for increasing agricultural production to meet the need of burgeoning population is to maximize productivity per unit of land. Systematic research into maximum yield production is yet to be undertaken in Pakistan. However, there are data available to indicate the outlines of high yield production technology in Pakistan. An attempt is made in this paper to review briefly the experiences of obtaining high crop yields and to identify what constrains maximizing crop yields in Pakistan.

　　2.巴基斯坦农业概貌 PAKISTAN AGRICULTURE: A PROFILE

　　为了估价作物生产的未来发展，下面概述了巴基斯坦的基本农业情况：

　　In order to appreciate the future developments in crop production, essential elements of agricultural scenario-in Pakistan are outlined below:

　　2.1.气候 Climate

　　巴基斯坦为大陆性气候，其特点是温度极冷极热、降雨变化剧烈和相对湿度较低。大部分地区是亚热带大陆干旱、半干旱地区。年平均降雨量从中南部的100毫米到喜马拉雅山麓的1250毫米。夏季季风季节的暴雨占总降雨量的70%，冬季占30%。除山区外，夏季很热，最高极端温度超过40度，冬季气候温暖，最高约20度，最低在冰点上下几度内。但在山区，冬季一般低于0度，常有降雪。

　　The country has a continental type of climate characterized by extreme temperatures, irregular rainfall and low relative humidity. Most part is arid or semi-arid in the sub-tropical continental zone. Average annual precipitation ranges between 100 mm in the south central part and more than 1250 mm in the Himalayan foot hills. About 70% of the total rainfall as heavy downpour in the summer monsoon months and 30% in winter. The summer months, except in the mountainous areas, are very hot, with a maximum temperature exceeding 40℃, and the winter months are mild, with a maximum temperature around 20°C and the minimum temperature a few degree about the freezing point. In the mountains, however, temperatures frequently fall below 0℃ and snow is common during winter.

　　2.2.土地利用 Land Use

　　巴基斯坦国土总面积为7961万公顷，其中耕地2107万公顷。耕地中的1650万公顷即80%是水浇地，其余是旱地。总种植面积为2189万公顷（1616万公顷一年一季，573万公顷一年数季）。粮食作物占55%，经济作物16%，豆类 7%，油料2%，蔬菜、水果和调料4%，其余16%。表1示出主要作物的种植面积、总产和单产。

　　Pakistan's total geographic area is 79.61 million ha, of which 21.07 million ha are cultivated. On the cultivated area 16.5 million ha or about 80% is irrigated and the remaining rainfed. Total cropped area is 21.89 million ha (16.16 million ha net sown and 5.73 million ha sown more than once). Food grains constitute 55%, cash crops 16%, pulses 7%, oilseeds 2%, vegetables, fruits and condiments 4% and others 16%. Table 1 shows area, production and yield of major crops.

(表：表1 主要作物面积、总产和产量(1990~91) )

Crop作物 Area面积 Production总产 Yield产量
('000 ha)千公顷 ('000 t)千吨 (kg/ha) 公斤/公顷
Wheat小麦 7,911 14,565 1,841
Rice (paddy)水稻 2,113 3,261 1,543
Maize玉米 845 1,185 1,402
Sugarcane甘蔗 884 35,989 40,720
Cotton (lint)皮棉 2,662 *9,628 615

注释：* bales; one bale = 170.09 kg 包；一包=170.09公斤
　　2.3.土壤 Soils

　　巴基斯坦大多数土壤由水成（冲积）或风成（黄土）母质发育而来，也有一些是当地母岩风化而成。砂质土壤矿物质由各种比例的云母、石英和长石组成。粘粒组成主要为伊利石和高岭石，也有少量蒙皂石、绿泥石和蛭石。从质地上看，约30%的土壤是粘土，35%是壤土，10%是砂土，其余土壤质地庞杂。

　　Most soils in Pakistan are derived from water-transported (alluvium) or wind-blown (loess) material, yet some have been formed by in-situ weathering of rocks. Sand mineralogy of soils constitutes varying proportions of mica, quartz and feldspars. Clay fraction is dominated by illite and kaolinite with small proportions of smectite, chlorite and vermiculite. From textural point of view, about 30% soils are clayey, 35% loamy and 10% sandy while the remaining have variable texture.

　　总之，巴基斯坦土壤是石灰性土壤，盐基饱和度高，pH值介于7.9~8.3。至于肥力状况，几乎所有土壤缺氮，约90%土壤低磷或中磷。钾的状况多为中到高。因碱性石灰性土壤的特性，微量养分有效性不高，特别是水稻土中缺锌，柑桔园中缺铜缺锌和苹果园中缺铁。也观察到缺乏镁、锰、硼的现象。硫的状况一般较好。

　　Pakistan soils are, in general, calcareous with a high base saturation and pH ranging between 7.9 and 8.3. As regards fertility status, almost all soils are deficient in N and about 90% are low to medium in P. The status of K is generally medium to high. Because of alkaline calcareous nature of soils, availability of micronutrient is a problem, particularly Zn in rice soils, Cu and Zn in citrus and Fe in apples. Deficiencies of Mg, Mn and B have also been observed. Sulphur status, in general, is satisfactory.

　　一些土壤受盐碱影响：约15%的灌溉面积有不同程度的盐化和苏打碱化，约10%的土壤受淹水之苦。

　　Some soils are affected by salinity-alkalinity: about 15% of irrigated area suffer from varying degrees of salinity and sodicity and about 10% from water logging.

　　3.巴基斯坦的高产作物生产经验 HIGH YIELD CROP PRODUCTION EXPERIENCES IN PAKISTAN

　　巴基斯坦作物产量低下（表1），增长速度也很低，截止1990年的十年中，小麦产量年增长1.5%、水稻0.3%、玉米0.9%、甘蔗0.8%、棉花4.4%。比起同期用肥量增长6.l%来说，这种情况令人担忧。化肥是一项昂贵的投入，似乎并不与作物的产量反应相符。如何打破作物产量徘徊的局面是应找到答案的一个严重问题。只有仔细地分析研究了这一现象后才能制订将来的作物增产战略。

　　Crop yields in Pakistan are low and the rates of growth have been dismally low: for the 10-year period ending 1990, the annual growth rate for wheat was 1.5%, rice -0.3%, maize 0.9%, sugarcane 0.8% and cotton 4.4%. The situation is particularly disconcerting when the rate of growth for fertilizer for the same period is considered which was 6.1%. Fertilizer, an expensive input, does not seem to reflect in crop yields concomitantly. How to break crop yield stagnation is a serious question warranting an explanation. Future strategy for crop yield improvements can only be devised effectively when this phenomenon is carefully and analytically studied.

　　巴基斯坦气候多样、土地适宜、有效水充沛，并有适当作物生产科学技术知识以取得高产，可参看表2。但是，试验产量和农民当地条件下所得产量之间存在巨大鸿沟，向增加作物产量的目标提出了挑战。全国作物产量只有试验产量的20~25%，其余75~80%的产量潜势尚未实现。也许作物管理有缺陷。也许要有更多的最高作物产量参数的信息。或许科学的作物生产技术需要示范推广到农场一级。

　　Pakistan is endowed with the climatic versatility, land suitability, water avahability and the appropriate technical knowledge on scientific crop production technology to produce high crop yields as can be seen from data in Table 2. However, the gap in crop yields between experimental and farmers' conditions is wide and poses challenge in the direction of maximizing crop yields. National crop yields are approximately 20-25 % of yields obtained under experimental conditions and 75-80% is the unrealized potential. Perhaps crop husbandry is amiss. Maybe more information on parameters of maximum crop yields need be generated. Or the scientific crop production technology need be demonstrated and transferred to farm level.

(表：表2 巴基斯坦试验条件下作物高产量与全国产量比较(吨/公顷) )

Crop 作物 Experimental or potential试验或潜在产量 National 全国产量 National as % of potential全国产量为潜在产量的%
Wheat小麦 8.0 1.8 22.5
Rice (paddy)水稻 9.5 1.5 15.8
Maize玉米 6.9 1.4 20.3
Sugarcane甘蔗 256.0 40.7 15.9
Potato马铃薯 38.1 10.4 27.3
Cotton棉花 7.9 1.8 22.8
Oilseeds油菜籽 2.7 0.8 29.6

注释：Sources资料来源: Sandhu, G. R. 1988; Hussain et al., 1992
　　在另一方面，有些先进农民利用配套作物生产科学技术获得了极高产量，甚至常常超过试验田的产量。以下列举数例：

　　Yet on other hand there are progressive farmers who obtain very high crop yields by practicing the scientific package of crop production technology. Quite often they even exceed yields obtained in experimental. fields. Some examples are cited below:

　　3.1.甘蔗 Sugarcane

　　信德省已研究出甘蔗高产技术，在私人农场上产量达405吨/公顷（Husain，1982）。本文第一作者曾访问过信德省的特达地区，那里甘蔗产量295吨/公顷。先进农民的甘蔗产量常为225~275吨/公顷，出糖率也较高为12.7%，而全国平均约8.5%。信德省较适合生产甘蔗，因其生产季较长，冬季温暖无霜、离海较近故大气湿度高。除有利的生长条件外，信德糖业股份有限公司在“蓝图计划”下推广的高产技术也保证了高产。热水处理后代种子，杀真菌剂处理种子，施肥（325-125-250 N-P2O5-K2O公斤/公顷）、深穴施钾肥、使用除草剂、叶施锌、锰和硼肥、良好的管理措施构成甘蔗高产技术的重要组成部分。甘蔗全国平均产量在过去10年中徘徊于40吨/公顷，与信德省先进农民所获275吨/公顷，旁遮普省和西北边境省的100吨/公顷形成鲜明对照，突出了巴基斯坦最高产量研究的意义。

　　Sugarcane yield maximizing technology has produced in Sindh as high yield as 405 t/ha at private farms (Husain, 1982). The senior author has visited a farm in Thatta area of Sindh where sugarcane yield of 295 t/ha was obtained. Yields in the range of 225-275 t/ha are common with progressive farmers. Sugar recovery has also been more: 12.7% against national average recovery of about 8.5%. Sindh Province is ideally suited for production of sugarcane because of its longer growing season, frost free mild winters and high atmospheric humidity due to its proximity to sea. Besides the conducive growing conditions, the sugarcane yield maximizing technology promoted by Sindh Sugar Corporation Limited under the Blue Print Programme promises high yields. Hot water treated progeny seed, fungicide treatment of seed, application of fertilizers (325-125-250 N-P2O5-K2O kg/ha), deep placing potash in holes, use of weedicides, foliar spray of Zn, Mn and B, and good management practices constitute the essential elements of maximum sugarcane; yield production technology. Sugarcane national yield stagnated at 40 t/ha for the last ten years versus high yields obtained by progressive growers around 275 t/ha in Sindh and more than 100 t/ha in the Province of Punjab and NWFP underlines the scope of maximum yield research in Pakistan.

　　3.2.棉花 Cotton

　　全国棉花产量从1981年的340公斤/公顷皮棉增加到1991年的750公斤/公顷。但有些农民获得籽棉产量高达5吨/公顷，相当于1.7吨皮棉/公顷。在试验条件下和农民田地的大田试验中已获得籽棉7.9吨/公顷和7.2吨/公顷的高产（Bhatti,I.M,等1981）。1991年在旁遮普省木尔坦地区，Sadiq Akbar Bokhari 先生私人农场的80公顷土地上，籽棉平均产量3.5吨/公顷，折合皮棉1.2吨/公顷，另外20公顷土地上籽棉4.5吨/公顷，折合皮棉1.5吨/公顷，推荐的农艺措施包括使用除草剂、农药、肥料（125-50-50 N- P2O5- K2O公斤/公顷）以及起垄种植棉花。6月5~30日种棉，11月至次年2月采收，11月底在4公顷站立棉株间套种小麦，单产小麦2.8吨/公顷。由棉麦和稻麦轮作造成的问题在作物高产种植制度一节探讨。

　　National cotton yields have appreciably improved from 340 kg/ha lint in 1981 to 750 kg/ha in 1991. However, farmers obtain seed cotton yields up to 5 t/ha equivalent to 1.7 t lint/ha. Seed cotton yield of 7.9 t/ha and 7.2 t/ha have been achieved under experimental conditions and under on-farm trials in farmers' fields (Bhatti, 1. M, et al, 1981). During 1991 at a private farm of Mr. Sadiq Akbar Bokhari in Multan area of Punjab, average yields of 3.5 t/ha equivalent to 1.2 t lint/ha from an area of 80 ha and 4.5 t/ha equivalent to 1.5 t lint/ha from an area of 20 ha were obtained. Recommended agronomic practices including the application of weedicide, pesticides, fertilizers (125-50-50 N-P2O5-K2O kg/ha) besides planting of cotton on ridges were followed. Crop was planted between 5-30 June and harvested between November and following February. Wheat was planted on 4 ha in standing cotton in the end of November and produced 2.8t/ha yield. Problem arising out of cotton-wheat and rice-wheat crop rotations is discussed under the section on crop yield maximization in cropping systems.

　　3.3.小麦 Wheat

　　达乌德股份有限公司在巴基斯坦组织的“小麦产量竞赛”在旁遮普省小麦灌区获得6.4吨/公顷的最高产量，其次，四个地区平均产量5.8吨/公顷。各地区12位农民的平均产量为5.6吨/公顷。古杰拉特地区旱地小麦的最高产量为3.6吨/公顷，其次为拉瓦尔品第、Jehlum和Campbelpur三个旱地小麦地区平均产量3.0吨/公顷。1975~76年全国平均小麦产量为：水浇地1.5吨/公顷、旱地0.7吨/公顷，1990~91年为水浇地2.0吨/公顷、旱地1.1吨/公顷，这些结果表明产量潜势由改进传统技术得以开发，并非采用科学技术。

　　Wheat yield contest organized by Dawood Corporation Limited (DCL, 1976) in Pakistan resulted in 6.4 t/ha top yield of irrigated wheat in Punjab followed by an average of 5.8 t/ha for four divisions. Average yield of 12 farmers in various districts was 5.6 t/ha. A maximum yield of 3.6 t/ha was obtained in rainfed wheat in Gujrat District followed by an average of 3.0 t/ha for 3 rainfed districts of Rawalpindi, Jehlum and Campbelpur. The national wheat yield in 1975-76 was 1.5 t/ha irrigated and 0.7 t/ha rainfed, and during 1990-91 was 2.0 t/ha irrigated and 1.1 t/ha rainfed wheat. These results indicate potential yields obtained following improved traditional technology, not necessarily the scientific technology.

　　3.4.水稻 Rice

　　为了估计1991年古杰兰瓦拉典型稻区先进农民的水稻产量，国家肥料发展中心（NFDC）与国家肥料经销股份有限公司(NFML)合作进行了一次快速随机抽样调查。结果表明，10位稻农在367公顷稻田上的平均产量为4437公斤/公顷，全国平均产量为1543公斤/公顷。这些农民一般每年种稻麦两季。388公顷小麦的平均产量为3411公斤/公顷，全国平均产量为184公斤/公顷。对农民的采访发现所用水稻品种为Basmati-385和IRRI-6号，小麦品种为Pak-8。小麦在11月底至12月初播种。农民通常只用氮、磷肥，只有两例使用钾肥。除两户农民外，其余农民都求助于农业推广站和国家肥料经销股份有限公司的指导。显然，他们并不是最高产量的农民，甚至他们所用作物养分也不平衡，不符合高产目标需要。

　　In order to have an estimate of rice yields obtained during 1991 by progressive farmers in a typical rice growing District of Gujranwala, a quick random survey was conducted by NFDC in collaboration with National Fertilizer Marketing Limited (NFML). Results show that ten rice farmers obtained an average yield of 4,437 kg/ha from an area of 367 ha against the national average yield of 1,543 kg/ha. These farmers generally planted two crops a year in rice-wheat rotation. The average yield of wheat for 388 ha was 3,411 kg/ha against the national average of 184 kg/ha. Farmers interviews revealed that rice varieties sown were Basmati-385 and IRRI-6 and wheat variety Pak-81. Wheat was sown in end November/early December. Farmers generally applied only N and P except in two cases where K was also included. All but two farmers sought advice from agricultural extension and NFML. Obviously these were not the maximum yield farmers; even their nutrient application to crop was imbalanced and not in keeping with high yield goal.

　　3.5.玉米 Maize

　　玉米是高雨量和山区的重要粮食作物。1990~1991年全国平均产量为1401公斤/公顷。过去15年来玉米产量没有多大长进，1975~76年玉米产量已达1294公斤/公顷。大约60%玉米种在西北边境省。玉米也在斯瓦比、曼塞赫拉、斯瓦特等一些特定地区种植。这些地区玉米产量高于其它地区。Byerlee和Husain 1992年报导了1983~1985年从斯瓦特地区取的224个玉米大田样品的数据。玉米平均产量为3.9吨/公顷，年际间很少变化。该产量远高于全国平均产量。另外，巴基斯坦农业研究中心（PARC）在旁遮普和西北边境省布置的最高产量计划示范田的玉米产量表明，通过更好的作用管理会使作物产量潜势更高（表3）。

　　Maize is an important grain crop especially for high rainfall and mountain areas. The national average during 1990-91 was 1401 kg/ha. There has not been substantial improvement in maize yield over the last 15 years when considered that maize yield in 1975-76 stood at 1,294 kg/ha. About 60% of maize area is in NWFP. Even there maize is grown in particular areas, such as Swabi, Mansehra and Swat. Yields are higher in these areas compared to other areas in the country. Byerlee and Husain, 1992, report data for 224 maize fields sampled in Swat from 1983 to 1985. Grain yields averaged 3.9 t/ha with little year-to-year variability. These yields are considerably higher than the national yields. Further, maize yield obtained in Punjab and NWFP plains in demonstration plots laid out by PARC under Yield Maximization Project (Chatha et al., 1989) show a great potential of increasing crop yields through better management Practices.

(表：表3 伊斯兰堡和木尔坦地区示范小区和农民大田玉米产量 )

Average yield 平均产量 Islamabad伊斯兰堡 Mardan木尔坦
yield产量(t/ha)吨/公顷 increase增产(%) yield产量(t/ha)吨/公顷 increase增产(%)
demonstration plots示范小区* 4.10 - 4.99 -
Farmers' yield 农民大田** 1.10 247 2.40 108
Total District 整个地区 0.84 388 1.80 177

注释：* Land projection included one deep plowing. Seed bed preparation done with one rotary harrow/disc harrow, recommended seed rate, recommended weedicide and insecticide applied. Fertilizer applied 103-92 N- P2O5 kg/ha. 整地包括一次深耕。用旋耕耙/圆盘耙制备种床，推荐播种量，推荐除草剂和杀虫剂。施用肥料103-92 N- P2O5公斤/公顷。 ** Estimated by Crop Maximization Project. 由作物最高产量计划估计
　　3.6.限制作物高产的因素 Constraints to High Crop Yields

　　作物生产限制因素是多样的：政策限制、制度限制、财政限制、技术限制、作物管理限制等等。全面讨论这些问题已超出本文范围。大田产量限制因子研究试验已在巴基斯坦收集了大量数据（Bhat-ti等1981；Shah等1981；Malik等1981；PARC1983）。表4概括了其中一些发现。迟播，尤其是小麦、种植密度偏低，尤其是水稻、草害病害蔓延和施肥不足且不平衡是重要限产因子。

　　Crop production constraints are of varied nature: policy constraints, institutional constraints, financial constraints, technical constraints, crop management constraints, etc. Full discussion is outside the scope of this paper. Considerable data have been collected in Pakistan under On-farm Yield Constraints Research Trials (Bhatti et al., 1981; Shah et al., 1981; Malik et al., 1981; PARC, 1983). Some of the findings are summarized in Table 4. Delayed planting, especially of wheat, sub-optional plant density, especially in rice, weed disease infestation, and inadequate and imbalanced fertilizer nutrient application are the important constraints.

(表：表4 高产作物产量限制因素(对产量差距的贡献%) )

Crop 作物 Plant density/ variety作物密度/品种 Fertilizer 肥料 Weeds/pest control杂草/病虫防治
Wheat 小麦 Irrigated灌溉地 17.0 (variety品种) 56.0 21.0 (weeds杂草)
Rainfed雨养地 36.0 (variety品种) 51.0 13.0 (weeds杂草)
Rice 水稻 IRRI 17.0 (density密度) 57.0 17 .0 (weeds杂草)
Basmati 42.3 (density密度) 35.8 16.7
Cotton 棉花 31.0 (density密度) 38.0 20.0 (pests病虫)
Maize (Rainfed) 玉米（雨养） 13.0 (density密度) 80.0 7.0 (weeds杂草)

注释：* Source 资料来源: Malik, D. M., et al, 1981,× Source资料来源 Bhatti, 1. M., et al, 1981, #Source资料来源: NFC, 1981
　　4.提高种植制度的作物总产量 MAXIMIZING CROP YIELDS IN CROPPING SYSTEMS

　　提高一种作物的产量是一回事，而提高种植制度的作物总产又是一回事。农民采用多熟种植（连作，套作和间作）以便最大赢利、使投入和劳动最经济。土壤和气候影响种植制度。在连作种植制度中，有三种主要类型：以小麦为主作、以水稻为主作和以棉花为主作，另有一些多元作物种植类型引入甘蔗、玉米、马铃薯和蔬菜等。这些种植制度也产生一些问题，如水稻、棉花、甘蔗后作小麦不得不迟播。一种解决办法是用向日葵代替迟播小麦。向日葵最佳播期为2月，6月就收获，给播种水稻留下充裕时间。春播向日葵也为白沙瓦谷地的农民提供了在甘蔗茬后取代迟播小麦的可能（Byerwll和Husain,1992）。还有适合雨养地区的种植制度，视雨量而定，还有适合山区的。在雨养农区，小麦是种植制度中的主角。除小麦、玉米和高梁/谷子外，可根据土壤适合程度和有效水分状况种植豆类和花生。

　　Maximizing yield for an individual crop is one thing and maximizing yields in a cropping system is another. Multiple cropping (sequential, relay and inter cropping) is practised by farmers to maximize his profits and to economize his inputs and labor. Soil and climatic variations influence cropping systems. Under the sequential cropping pattern there are three major systems i.e. wheat-based, rice-based and cotton-based cropping systems, besides other diversified systems bringing in sugarcane, maize, potatoes, vegetables, etc. Cropping systems also give rise to such problems as late planting of wheat after rice, cotton or sugarcane. One solution is to substitute sunflower for late planted wheat. The optimal time to plant sunflower is February. It is harvested in June leaving enough time to plant rice. A spring sunflower crop also offers the farmer the opportunity to substitute for late planted wheat after sugarcane in Peshawar valley (Byerlee and Husain, 1992). And then there are cropping systems for rainfed area, depending on rainfall, and for mountain areas. Wheat is dominant in all cropping systems in the rainfed tract. Besides wheat, maize and sorghum/millet, pulses and groundnut are the crops grown depending on the soil suitability and moisture availability.

　　即使已采用了连作种植制度，但是直到最近还是只对一种作物进行施肥。许多发展中国家有间作的传统，尤其对小农户至关重要。这是因为在其有限耕地上集约种植某些作物以满足家庭需要和降低气候不良和病虫危害造成绝产的风险。因此，应该研究包括间作在内的种植制度而不仅为某种作物寻找合适的施肥方案。

　　Until recently the fertilization practice has been for a single crop, even though the sequential cropping system has been followed. The inter-cropping system is considered traditional for many developing countries and is of special importance to small farmers. This is due to growing a variety of crops intensively in their small holdings for fulfilling home needs and insulating risk against complete failure due to aberrant weather and/or pest/disease attack. Thus there should be studies for finding an optimal fertilizer schedule based on a cropping system including intercropping systems rather than for a single crop only.

　　例如，研究业已表明，在麦稻和麦棉轮作中，如果对小麦施足磷肥，在稻季和棉季中可少施磷肥，但反过来不行（表5）。

　　For example, research has shown that in wheat-rice and wheat-cotton rotations, it may be possible to cut down full dose of phosphate application to rice and cotton crops if phosphate is adequately applied to wheat but not vice versa.

(表：表5 水稻小麦轮作中施磷对作物产量的影响 )

P applied(26kgP/ha)to 施磷26公斤P/公顷给 Mean grain yield平均籽粒产量(t/ha)吨/公顷
rice水稻 wheat小麦
both rice and wheat 水稻和小麦 6.55 4.18
wheat only 小麦 6.56 4.10
rice only 水稻 6.48 2.39

注释：Source资料来源 :Meelu et al., 1992
　　种植制度的产量不仅可以提高，也可以为农民带来更多的经济收入。Byerlee和Husain 1952年报导过木尔坦地区传统和新式（引入向日葵）两种种植制度的营利情况（表6）。

　　Not only can yields be maximized in cropping systems but also it brings more financial returns to the farmer. Byerlee and Husain, 1952, report profitability of cropping patterns in Mardan District both for traditional and new (incorporating sunflower) cropping systems.

(表：表6 木尔坦地区不同种植制度的盈利 )

Cropping systems (two years) 种植制度（两年） Profitability盈利 ($/ha/yr)美元/公顷/年
Wheat-Sugarcane intercropped-ratoon cane 小麦-甘蔗间作-截根甘蔗 91.4
Wheat-maize-wheat-maize 小麦-玉米-小麦-玉米 189.0
Wheat-maize-sunflower-maize 小麦-玉米-向日葵-玉米 216.3
Maize-sunflower intercropped peas-maize 玉米-向日葵间作豌豆-玉米 327.2

　　5.赢得最高产量的较好管理措施 BETTER MANAGEMENT PRACTICES FOR YIELD MAXIMIZATION

　　作物高产技术已是众所周知，但在农场一级没有良好的贯彻执行。已经证明的作物高产配套科学技术要求改良品种、作物管理措施和使用投入等应针对特定农场条件。不能在此全面讨论所有技术构成要素，以下只就农场管理措施作一讨论。

　　Crop production technology for high yields is known. It is its implementation at farm level which is far from adequate. Proven package of scientific technology for maximum crop yields requires that improved seed, crop management practices and the use of inputs should be fine-tuned to farm-specific-situations. Complete discussion of all components of this technology is not possible for lack of space. Only the role of farm management practices is discussed.

　　5.1.有效利用肥料 Efficient Fertilizer Use

　　肥料是作物生产配套科学技术的重要组成，其贡献通常占作物生产的40~60%，施肥与作物产量有正相关。亚太地区的产量范围低者只有1吨/公顷，高者达6吨/公顷。其中许多国家低于2.5吨/公顷，他们的养分用量常低于100公斤/公顷，大大低于最佳水平（IFA 1992）。巴基斯坦在发展肥料使用方面取得长足进展（NFDC,1989）：总养分（N、P2O5、K2O）/公顷1960~61年为1.7公斤，1970~71年为14.7公斤，1980~81年为52.2公斤，1990~91年为89.8公斤。各个十年期间的年增长率分别为：截止至1970~71为24.6%，1980~81为14.3%和1990~91为5.8%。但如表7所示肥料利用率相当低，可能有各种解释，但养分间的不平衡施用和作物管理不良好象是最重要的原因（Tahir-Saleem，1992）。

　　Fertilizer is a vital component of scientific package of crop production technology and, in general, contributes from 40-60% to crop production. There is a positive relationship between fertilizer use and crop yields. Yields in the Asia Pacific Region range from as low as I t/ha to as high as 6 t/ha with many countries below 2.5 t,/ha. In the latter case nutrient applications are frequently below 100 kg/ha, well below the optimal level (IFA, 1992). Pakistan has made a phenomenal progress in the development of fertilizer use (NFDC, 1989): total nutrients (N, P2O5, K2O) use per hectare in 1960-61 was 1.7 kg/ha which increased to 14.7 kg/ha in 1970-71, 52.2 kg/ha in 1980-81 and 89.8 kg/ha in 1990-91. The rates of annual growth for the ten-year periods ending 1970-71, 1980-81 and 1990-91 were 24.6%, 14.3% and 5.8%, respectively. However, the efficiency of fertilizer use is very low as shown by data in Table 7. There could be various explanations but imbalance among nutrients use and poor crop husbandry seem to be the most important reasons (Tahir-Saleem, 1992).

(表：表7 全国平均产量和肥料使用量指数 )

Period ending 1990-91截止1990-91时期 Crop yield indices 5* major crops 5种作物产量指数 Food** crops 粮食作物 Fertilizer use indices肥料使用量指数
15-year 15年 133 112 345
10-year 10年 120 106 175

注释：* Wheat, maize, rice, sugarcane and cotton 小麦、玉米、水稻、甘蔗和棉花。 ** All five crops except cotton 除棉花外所有作物。
　　不仅施肥推荐应更针对具体地点，而且提高养分利用率也应以提高种植制度中作物产量为目的。另外，应在综合植物养分系统中施用肥料。这一方法，为每个农场的种植制度寻求利用各种植物养分资源，诸如矿质肥料、有机肥料、作物残体和生物固氮，并且在保护环境和资源的同时，给农民提供更好的持续发展生产的机会。

　　Not only should fertilizer recommendations be made more site-specific but also the efficiency of applied nutrients be enhanced with a view to increasing crop yields in cropping systems. Further, fertilizer use should be practiced in Integrated Plant Nutrition System (IPNS). This approach seeks to use various sources of plant nutrients, mineral fertilizers, organic manures, crop residues and biological nitrogen fixation for each farm’s cropping system and offers the farmers the best opportunity for sustainability while protecting the environment and conserving the resources.

　　5.2.稻麦制中的免耕 Zero Tillage in the Rice-wheat Pattern

　　巴基斯坦约有150万公顷积土地采用这种种植方式。该种植方式中最重要的小麦限产因素是迟播。1984年60%的小麦在12月1日后播种，30%小麦在12月15日后，而小麦最高产量的最适播期为11月中旬（Byerlee等，1984）。估计在最佳播期后每迟一天减产小麦20~30公斤。这也被印度的同类试验结果所证实（Randhawa等，1981）。结果还表明迟播明显降低氮肥效率（Saunders，1988）。

　　This cropping pattern is grown on about 1.5 million hectares in Pakistan. The most important limiting factor for wheat yield in this cropping system is late planting. During 1984, 60% of wheat was planted after 1 December and 30% after 15 December when the optimal planting date for maximum wheat yield was up to middle of November (Byerlee et al., 1984). It is estimated that wheat yields decline on an average 20~30 kg per day for every day’s delay after the optimal planting date. This is corroborated by results from other trials in India (Randhawa et al., 1981). Results also show that N-efficiency decreases significantly with late planting (Saunders, 1988).

　　为减少稻麦两季间约20天的拖延时间，1984~1992年在巴基斯坦研究成功采用免耕技术（用特别设计的条播机直接在稻茬田上播种小麦）（ASlam等，1989）。这项新技术的关键是把麦种播于接触土壤湿度好的部位以保证齐苗。1986~87年6个点的结果表明，使用合适的机具免耕，平均小麦产量3677公斤/公顷，传统耕作只有2598公斤/公顷；高产来自早播小麦24天。然而，目前这种技术的主要限制是农民没有可用的条播机。这一问题已有所强调并应迅速解决。

　　In order to reduce the turnaround time of about 20 days between rice and wheat, the use of zero-tillage technology (planting wheat directly into rice stubble with a specially designed drill) has been successfully researched in Pakistan from 1984 to 1992 ( Aslam et al., 1989). The key to this new technology is the placement of the wheat seed in good soil moisture contact to ensure good seedling emergence. When this was done with the proper equipment, results from six sites in 1986-87 showed an average wheat yield of 3677 kg/ha with zero tillage against 2598 kg/ha with conventional tillage; higher wheat due to earlier planting of wheat by 24 days. However, the main constraint to this technology at present is the availability of a suitable drill for the farmer. This problem is being addressed and should be resolved soon.

　　工业较发达国家已采用免耕或少耕技术，其代价是使用更多除草剂防治可能出现的草害。表8的资料和一些大田观察资料表明，因土壤较少被扰动，免耕比传统耕作的农田杂草群体更少。

　　In more industrialized countries, zero and reduced tillage has been adopted but usually at the expense of using more herbicides to control occurring weed problems. Data in Table 8 and numerous field observations show that because the soil is less disturbed, zero tillage results in less weed populations than conventional tillage.

(表：表8 免耕对出苗和杂草密度的影响(1985~86年资料) )

Method 方法 Plants emerged出苗数 Number of weeds/m2 杂草数/米2
grasses禾本科 broad leaves宽叶杂草 Total总数
Zero tillage 免耕 114 59 54 113
Farmer Practice农民的措施 96 72 90 162
Significance 显著性 0.05 0.05 0.05 0.05

　　虽然免耕技术为稻麦制中播种小麦提供了潜力巨大的技术突破，但有二个问题值得注意：后茬水稻螟虫群体增多的危险和施肥，尤其是施氮肥的问题。对于第一个问题，只要农田灌水和施肥，螟虫幼虫孵化出来后不会活得很长。它们只能在未耕、无灌水的稻田中生存。后一个问题也可由设计新的免耕条播机、播种同时施肥来克服。但还需要研究免耕的长期影响，以确定这项技术将来是有利还是有害。特别是病害的发生如叶枯萎（Helminthoporium sativum）需要长期监测。

　　Although zero tillage technology presents a potentially dramatic breakthrough for planting wheat in rice-wheat system, there are two issues meriting attention: danger of increasing population of stemborers for the following rice crop and the application of fertilizer, particularly N fertilizers. As to the former, the stemborer larvae do not survive long enough to hatch out as long as the field is irrigated and fertilized. They only survive in unplowed rice fields where no irrigation is given. The latter can be overcome by either designing a zero-till seed drill that places fertilizer in the soil at planting time. However, long term issues of zero tillage need to be explored to determine whether future problems or benefits may arise for this technology. In particular, the buildup of diseases, such as leaf blights (Helminthoporium sativum) need to be monitored over time.

　　将来的最高产量研究应包括免耕和少耕，因其提供了获得最佳播种和降低成本提高产量的途径。

　　Zero and reduced tillage should be included in future maximum yield research because it provides a way of obtaining optimum planting and increased yields at less cost.

　　5.3.棉花-小麦轮作中小麦迟播的难题 Dilemma of Late Wheat Planting in Cotton-Wheat Rotation

　　棉麦轮作中同样发生小麦迟播的问题。此时，农民为了明显的经济利益宁可采摘晚棉而推迟种麦。据报导，2/3的小麦在棉花采收后的12月中旬以后播种，这时减产风险很高（Byerlee和 Husain,1992)，农民似乎合理地权衡多采一茬棉花的收益和迟播小麦的损失。有意义的是，在棉花收获前的小麦最佳播期，在预先灌水的棉田中播撒浸透水的麦种所提供的结果表明，这是一种解决问题的办法。在稻麦制中这种播种方法还需要进一步研究。

　　Similar problems of late planting of wheat occur in the cotton-wheat system. In this case farmers prefer to take the last cotton picking and delay wheat planting for obvious economic reasons. It is reported that two-third of wheat fields after cotton are planted after mid-December when the risk of yield loss is very high (Byerlee and Hussain, 1992). Farmers appear to rationally weigh the benefits of an additional cotton picking with the costs in terms of planting wheat late. Interestingly, broadcasting soaked wheat seeds into pre-irrigated cotton fields before cotton harvest and at the best wheat planting date is providing data that show this may be the answer to this problem. More research is needed on this seeding method for both rice and wheat.

　　5.4.巴拉尼地区的深耕 Deep Tillage in Barani Areas

　　巴基斯坦旱地小麦的产量非常依赖冬季降雨和土壤剖面中的储水。浅耕造成土表下20~30厘米处坚硬的犁底层。这限制根系生产以致大大减产。研究表明，用有壁犁在季风季节深耕可解决这一问题。平均说来，深耕小麦可增产25%，1982~1988年从农民大田试验收集的数据（Razzaq等，1990;Khan等，1990）表明，深耕对旁遮普省拉瓦尔品第地区的小麦产量大有益处。这种好处由6月季风季节之前用有壁犁整地翻耕得到，然后土地在季风季节休闲直到11月种麦。1983年有壁犁耕翻（30厘米深）的效果与深松犁（45厘米深）、凿形犁（25厘米深）和农民的播种机（10厘米深）加以比较，只有有壁犁的效果明显好于播种机（Khan等，1986）（图1）。马铃薯、蚕豆和蔬菜（Rouse和Stone，1980）、蓖麻、红小豆和珍珠小米（Reddy等，1983）以及中国种植的小麦（Zhao等，1986）都报道过类似的结果。巴基斯坦的研究表明园盘耙耕和有壁犁耕的小麦产量比播种机耕更好（Sheikh，1983）。

　　Rainfed wheat yields in Pakistan are very dependent on winter rainfall and stored water in the soil profile. Shallow cultivation has resulted in a hard plough layer 20-30 cm below the soil surface. This limits root growth and reduces yields substantially. Research has shown that deep tillage with a moldboard plough in the monsoon season can overcome this problem. On an average, with deep tillage, wheat yield can be increased by 25 per cent. Data obtained from farmer field trials from 1982 to 1988 (Razaq et al., 1990; Khan, et al., 1990) show a significant benefit of deep tillage on the yield of wheat in Rawalpindi District of the Punjab. This benefit was obtained by using a moldboard plough to prepare the soil in the pre-monsoon period in June. The fields were left fallow in the monsoon season and then planted to wheat in November. The effect of moldboard (30 cm deep) ploughing was compared with a subsoiler (45 cm deep) chisel (25 cm) plough and farmer's cultivator (10 cm deep) in 1983 and only the moldboard gave significant benefits over the cultivator (Khan, et al., 1986) .Similar benefits have been reported for potato, broadbeans and vegetables (Rouse and Stone, 1980), castor, redgram and bajra (Reddy et al., 1983) and for wheat in China (Zhao et al., 1986). Research in Pakistan has shown better wheat yields with a disc and moldboard plough as compared to a cultivator (Sheikh, 1983).

(图：图1 季风季节前耕作处理对小麦产量的影响)

　　巴基斯坦拉瓦尔品第地区的农民从季风季节开始到种麦，平均用拖拉机或畜力犁耕翻8次土壤。据报导，一些农民要耕20次。农民用这种耕作措施除草并在种麦前的休闲期保墒。

　　Farmers in Rawalpindi District of Pakistan tractor cultivate or animal plough their fields on average 8 times from the beginning of the monsoon until wheat planting. Some farmers even report more than 20 passes during this period. This tillage practice was done by farmers to control weeds and conserve moisture during the fallow period before the wheat crop.

　　这种耕作制度造成耕层下的紧实层，限制了水分渗入土壤剖面，造成更多迳流，当在l.5米深的坑中冲洗根系揭示出紧实层也限制根系发育（图2，Kham等，1986）。有壁犁深耕比播种机耕的好处可解释为在土壤剖面中储存了更多水分，又有更多的根系吸取了这些水分。

　　This tillage system has resulted in compaction occurring below the plough layers. This restricts percolation of water into the soil profile and results in more run-off. Rooting was also shown to be restricted by this compact layer when rooting profiles were exposed by washing the soil on the face of 1.5 m deep pits (Fig.2; Khan et al., 1986). The benefits of deep ploughing with a moldboard could be explained by more moisture in the profile and more root volume to extract this soil moisture compared to the cultivator system.

(图：图2 1983~84年拉瓦尔品第地区春季2月干旱后播种机和有壁犁翻耕处理的小麦根系剖面)

　　有壁犁耕翻另外的好处是杂草明显减少，杂草和草种被有壁犁翻耕深埋，而且旱地根腐病（Fusarium和Helminthosporium sp)减轻，这种病在旱年中造成缺苗问题（Khan等，1986；Razzaq等，1990)。将来需要研究紧实问题的动力学以确定需要几次有壁犁深耕。

　　Additional benefits from the moldboard ploughing were significantly less weeds in the moldboard plots, weeds and weed seeds were buried by ploughing, and less dryland root rot (Fusarium and Helminthosporium sp) which can be a problem for plant establishment in dry years (Khan et al., 1986; Razzaq et al., 1990). Future research needs to study the dynamics of the compaction problem to determine how frequent moldboard or deep tillage is needed.

　　5.5.病虫害防治 Pest Management

　　根据1975年农业咨询委员会的报告和其它一些研究，平均各种作物潜势产量的35~40%因病虫害损失掉。粗略估计年损失约达80万美元。政府采取放开个体农药市场的政策使农药消费从1981年的3677吨增加到1990年17442吨。尽管农药使用水平提高，据信巴基斯坦的用药量仍低于理想水平。根据一项估计，巴基斯坦只有总耕种面积的13%喷撒了农药，而其余87%的农场完全没有植物保护。农药市场的主要用户是棉田，占巴基斯坦全部农药用量的80%以上。过去十年中，棉田植物保护的面积由15%增加到75%。增加植保面积的结果直接由全国棉花生产水平提高近乎100%得到反映。水稻、甘蔗、小麦、水果和蔬菜的植保面积只限于播种面积的15~20%。

　　According to the Agriculture Enquiry Committee Report of 1975 and some other studies, on an average, 35-40% of the potential yield of our crops is lost due to damage by insects, pests and diseases. According to a rough estimate the loss is around US$ 800,000 per annum. The policy steps taken by the Government in liberalizing privatization of marketing of pesticides has resulted in increase in consumption of pesticides from 3,677 mt in 1981 to 17,442 mt in 1990. Despite this level of pesticides usage, consumption in Pakistan is still considered below the desired level. According to an estimate, only 13 % of our total crop hectareage receives pesticide cover, while the remaining 87 % of the farms completely lack plant protection. The major share holder of the pesticide market is cotton which alone accounts for over 80% of the total pesticide consumption in Pakistan. During the last 10 years, plant protection coverage to the cotton crop has increased from 15 % to around 75 %. The result of increased plant protection coverage is directly reflected in almost 100% increase in the production of cotton on the national level. The plant protection coverage in other major crops such as rice, sugarcane, wheat, fruits and vegetables is only limited to 15-20% of the cropped area.

　　5.6.除草 Weed Control

　　杂草可夺去一大部分作物产量。因杂草泛滥作物平均产量损失20~25%，完全绝产也并非罕见。根据英国海外发展署最近的一项报告，南亚国家，包括巴基斯坦7项最严重的病虫草害中，3项是杂草。几年前Borlaug博士指出，只要简单地改善杂草管理，巴基斯坦就能达到小麦自给。

　　Weeds can take a heavy toll of crop production. Because of weed infestation, crops suffer 20-25% reduction in yield on the average and complete crop failures are not uncommon. According to a recent report of the Overseas Development Agency of U.K, out of seven most important pests in the South Asian countries, including Pakistan, three are weeds. Dr. Borlaug pointed out several years ago that Pakistan could achieve self-sufficiency in wheat simply through improving weed management.

　　大田调查表明，小粒?草（(phalaris minor)是旁遮普省稻麦制中小麦的主要问题，几乎l/3的大田损失产量20~35%。一些田块受野燕麦（Avena fatua）和黑麦草（Lolium spp）的侵害。1984年的调查表明28%的大田中度或严重受到小粒?草的侵害，这些田产量为1.4吨/公顷，而无草害田块产量是1.9吨/公顷。

　　Field surveys show that Phalaris minor is a major problem in wheat in the rice-wheat system of the Punjab, accounting for a loss of over 20-35% of yield in nearly one-third of fields. Some fields are infested with wild oats (Avenafatua) and rye grass (Lolium spp.). Twenty-eight per cent of fields in the 1984 survey were moderately or severely infested with Phalaris minor and these fields yielded 1.4 t/ha compared to 1.9 t/ha for fields without weeds.

　　一些农民田地中小粒?草侵害严重，他们将播期推迟到气候凉爽、草籽发芽后，虽然尚未普及，但除草剂可控制这种杂草减少播期推迟现象。最近几年，使用除草剂开始迅速增多，1984年除草剂的使用不过5%，而1988年已达17%（Byerlee和Husain，1992）。

　　Some farmers whose fields are seriously infested with Phalaris minor delay wheat planting until cool weather stimulates germination of weed seeds. Although this practice is not widespread, the use of herbicides to control this weed is one way to reduce planting delays. In recent years, herbicide adoption has started to increase quite rapidly. From less than 5% adoption in 1984, herbicide use had spread to 17% of farmers in 1988 (Byerlee and Husain, 1992).

　　旁遮普省的水稻显示出草荒抵消了施肥效益。IRRI-6号水稻通过适当除草增产22%，由2859公斤/公顷增加3689公斤/公顷。发生草害的田块的施肥增产名不符实，而在除草的田块中施肥增产72%（Majid,A,1987）。在另一个试验中(Sadig和Habib,1988)，有草对照处理上施肥150-100（N-P2O5公斤/公顷）玉米产量只从708公斤增加到1265公斤/公顷，而除草处理产量从未施肥的1292公斤增加到施肥的3383公斤/公顷。

　　How weed infestation will offset the benefit of fertilizer use is demonstrated on rice in Punjab. Yield of IRRI-6 rice increased by 22 % from 2,859 kg/ha to 3,689 kg/ha, by proper weed control. The increase in yield by fertilizer was only nominal in weed infested plots, while it was 72.5% in weed controlled plots (Majid, A., 1987). In another experiment (Sadiq and Habib, 1988) maize yield in weedy check treatment increased from 708 kg/ha to 1,265 kg/ha with 150-100 (N-P2O5 kg/ha) fertilizer. However, in treatments with weed control, maize yield increased from 1,292 kg/ha in no-fertilizer treatment to 3,383 kg/ha in fertilizer treatment plot.

　　5.7.植株密度 Plant Density

　　单位面积上适当株数是取得最佳产量的重要因素。例如，种植密度低则限制水稻产量。据水稻研究所Kala Shah Kaku 1987年的调查，每公顷13万株的水稻比推荐的20万株减产20%。这也负面影响肥料效率。低密度是由于插秧季节缺少劳力，可通过制造和引进机械插秧机适当提高大田秧数。另一方面，玉米籽粒产量常受植株密度过高之害，因农民关心通过玉米间苗提供饲草。

　　The proper number of plants per unit area is crucial for obtaining optimal yields. For example, rice production is constrained with low plant population. According to a survey conducted by Rice Research Institute, Kala Shah Kaku in 1987, a population of 130,000 plants/ha was reported against the recommended population of 200,000 plants and this resulted in reduction of yield by 20%. This also adversely affects fertilizer efficiency. Low population is due to shortage of labor at the time of transplanting and may be overcome by fabrication and introduction of mechanical transplanters suitable for transplanting the seedlings raised in the field. On the other hand, maize grain production suffers from high plant density due to farmers' concern for fodder through maize thinning.

　　5.8.改良盐碱地 Ameliorating Saline-Alkali Conditions

　　盐碱是巴基斯坦土壤的严重问题，受盐害土壤的作物产量低是因为过量盐分的直接毒害作用和有害影响水分和养分的吸收。在可能的情况下通过石膏处理、灌水和遵循适当的种植顺序淋洗盐分和栽培耐盐品种改造盐碱地可显著提高作物产量（Chandhry和Dhaidullah，1988）

　　Salinity-alkalinity is a serious soil problem in Pakistan and crop yields in salt affected soils are low due to direct toxic effects of excess salts and impaired absorption of water and nutrients. Crop yields can significantly be improved through ameliorating the saline-alkali conditions by treatment with gypsum, leaching salts by irrigation and by following proper cropping sequence and tolerant cultivars where possible (Chaudhry and Obaidullah, 1988).

　　6.对巴基斯坦最高产量研究的建议 PROPOSAL FOR MAXIMUM YIELD RESEARCH IN PAKISTAN

　　本文强调了使一季商品作物达到最高产量。这提供了影响一季作物最高产量的因素的有用信息。但在南亚，大多数农民一年种二到三季，因此有必要进行进一步的最高产量研究以获得整个种植制度最高产量的资料。

　　The paper has emphasized on maximizing yields of a single commodity crop. This provides useful information on factors responsible for maximizing single crop yields. However, in South Asia, most farmers grow two or even three crops per year on their land and so it is necessary to take future yield maximization research one step-further so that information can be obtained on maximum yields for a cropping pattern.

　　巴基斯坦没有最高产量研究（MYR）的系统工作。因此，强烈地感觉到应在巴基斯坦开展最高产量研究，因其有助于认识限制作物实现最高产量的因素。这种研究应集中于各种种植制度而不是单一作物，因为我们的目标不仅是获得高产、而且要保证农民在长期保持土壤肥力的同时获得最高经济收入。PPIC印度项目发起了印度的最高产量研究，特别是卢迪亚纳的旁遮普农业大学(Naraag,1991)。建议PPIC能考虑发起巴基斯坦的最高产量研究。

　　There has been no systematic work undertaken in Pakistan on maximum yield research (MYR). It is, therefore, strongly felt that MYR should be undertaken in Pakistan because this kind of research helps to identify the constraints which limit crops to realize the maximum, yield potential. This research should focus on various cropping systems, rather than individual crops because we should not aim only at to obtain high yields but also need to assure the farmer the maximum financial return while preserving soil fertility for the long term. PPIC India programme sponsors MYR in India particularly at Punjab Agricultural University Ludhiana (Narang, 1991). It is recommended that PPIC may consider sponsoring MYR in Pakistan.

　　为提高肥料利用率、开发利用替代更新的植物养分来源，国际粮农组织建议根据综合植物养分概念制订一套种植制度的施肥方案以保证利用所有可用的植物养分资源与矿质肥料互补（Roy和Braun，1982）。

　　In order to increase fertilizer use efficiency and to develop the use of alternative renewable sources of plant nutrients, FAO recommends that it should be essential to develop fertilizer schedule for a cropping system based on the integrated plant nutrition concept ensuring the use of all available plant nutrition sources complementing mineral fertilizers (Roy and Braun, 1982).

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