Sewage Sludge: An Important Biological Resource for Sustainable Agriculture and Its Environmental Implications

Intensive farming generally needs large addition of organic matter to maintain fertility and enhance crop yields. Sewage sludge/biosolids are by-products of municipal and industrial wastewater treatment and a rich source of organic nutrients. Sewage sludge having high content of organic matter, macro- and micro-nutrients, can be used as fertilizer/soil conditioner for food, vegetable crop, horticultural plants and pasture, which in most cases can be beneficially recycled. In the past sewage sludge was regarded as a waste product due to expected high level of contaminants such as pathogens, pollutants and synthetic materials discharged in sewer from homes and industries, which were often incinerated, dumped in occasion or land fill. As a result of rapidly increasing population, urbanization and industrialization, wastewater production and sewage sludge generation have increased manifold. Due to high cost of mineral fertilizers and escalating trends in their prices, there is an increasing trend of using sewage sludge in agriculture, especially under intensive cropping in arid and semi arid regions of the country. Therefore, application of sewage sludge to agricultural soils may be sustainable and economical due to nutrient cycling and disposal of sewage sludge. However, there may be a risk in use of sewage sludge due to potentially harmful contents present in the sludge such as heavy metals and pathogens. This paper, therefore, presents a review on various aspects of sewage sludge used in agriculture.

Effect of Tillage and Nitrogen on Wheat Production, Economics, and Soil Fertility in Rice-Wheat Cropping System

Conservation tillage and nitrogen may improve soil fertility, yield and income on sustainable basis. The aim of this study was to evaluate the impact of three tillage systems viz. zero (ZT), reduced (RT), and conventional tillage (CT) and five N rates (0, 80, 120, 160, and 200 kg·N·ha-1) on yield and yield components, soil organic matter (SOM), total soil N (TSN), and income of wheat (Triticum aestivum L.) grown after rice (Oryza sativa L.). Nitrogen rates significantly affected yield and yield attributing characters with highest values recorded at200 kg·N·ha-1. Mean maximum grain yield (6390 -6845 kg·ha-1), net benefit (1359 - 1460 US$ ha-1), and benefit cost ratio (5.6 - 5.7) could be achieved at 160 to200 kg·N·ha-1. The tillage systems produced similar yield and yield components except spikes m-2. The SOM and TSN were highest in ZT compared to other tillage systems. Though tillage × N interactions were not significant for most of the parameters under study, the overall effect of ZT with200 kg·N·ha-1 appeared to be most favorable compared to RT and CT. Zero tillage resulted in highest number of spikes m-2 (304.4), SOM (9.6 g·kg-1) and TSN (0.5 g·kg-1) with200 kg·N·ha-1. The results suggest that ZT with200 kg·N·ha-1 was optimum and sustainable strategy to achieve higher yield and income and also to improve SOM and TSN on silty clay soil.

Impact of Tillage and Herbicides on Weed Density, Yield and Quality of Cotton in Wheat Based Cropping System

Conservation tillage may improve yield of cotton in addition to improvement in soil quality if practiced for longer period. However, the practice may not be productive in short-term particularly when severe weeds are infesting the crops such as Cynodon dactylon, Conyza canadensis, Tribulus terrestris, and Cyperus rotundus, etc. Recent studies indicate that conventional tillage （CT） is more productive than zero tillage （ZT）/reduced tillage （RT）. Performance of cotton under three tillage systems, viz., ZT, RT and CT; and five herbicides, i.e., haloxyfop-R-methyl 10.8 EC （108 g a.i. ha^-1）, lactofen 24 EC （168 g a.i. ha^-1）, haloxyfop 10.8 EC ＋ lactofen 24 EC, hand weeding, and weedy check were evaluated during 2010-2011 at Gomal University, D.I.Khan, Pakistan, to explore the best management option for effective weed control, enhanced yield and quality of cotton grown after wheat. The results revealed that hand weeding and Haloxyfop as post emergence alone or in combination with Lactofen reduced weed density to the minimum irrespective of the tillage systems. Excessive rainfall and cooler temperature limited cotton growth and yield in 2010. The adverse weather conditions had more adverse effect on boll weight under ZT and RT than CT. Haloxyfop ＋ lactofen produced higher seed cotton yield in RT than ZT, however, it could not exceed CT. Broad-spectrum herbicides x CT produced the highest number of bolls/plant, boll weight and seed cotton yield. Fiber quality and net returns were also the highest in broad-spectrum herbicides x CT. In conclusion, broad-spectrum herbicides under CT were more productive in wheat based cropping system on silty clay soil of D.I.Khan.

Integrated Weed Management Through Tillage and Herbicides for Wheat Production in Rice-Wheat Cropping System in Northwestern Pakistan

Conservational tillage （CT） in combination with broad spectrum herbicide may be more efficient and economical in controlling weeds, reducing cost of cultivation, and enhancing wheat yield. Field experiments were carried out to evaluate the effect of tillage and herbicides on weeds and wheat yield under rice-wheat cropping system （RWCS）. The results indicated that broad spectrum herbicides particularly, carfentrazone ethyl ester＋ isoproturon （Affinity 50 WDG） reduced weeds density by 93 and 95% compared to control and also produced the maximum grain yield （6 818 and 6 996 kg ha-l） and HI （harvest index, 44.7 and 44.6%） in 2007-2008 and 2008-2009 growing seasons, respectively. The maximum weeds infestation and the lowest yield were recorded in control. Tillage methods significantly influenced grain yield and HI, while no significant effect on all other parameters. The overall mean yield was significantly higher in zero tillage （5 575 kg ha-l） and reduced tillage （5 584 kg ha-l） compared to CT （5 479 kg ha-^-1）. Besides increasing wheat yield, Affinity 50 WDG and zero tillage are important weed management practices that can be integrated into wheat production in RWCS. However, in case of perennial weeds or insect pests＇ infestation, CT in combination with Affinity 50 WDG would be more productive than conservation tillage.

Ethnobotanical Studies on Dwarf Palm (<i>Nannorhops ritchieana</i>(Griff.) Aitchison) and Date Palm (<i>Phoenix dactylifera</i>L.) in Dera Ismail Khan, KPK, Pakistan

This paper is based on research work conducted during 2008-2010 in Dera Ismail Khan (D. I. Khan) District, Pakistan, to investigate Socio-Economic Impacts of Dwarf Palm (Nannorhops ritchieana) and Date Palm (Phoenix dactylifera) on the local inhabitants. A questionnaire for data collection of Dwarf Palm was designed and local people were interviewed. The main Dwarf Palm (Mazri) areas are lying between the Koh-i-Surkh and Marwat hill and yielding about 1000 tons of mazri leaves annually. Date Palm plantations are concentrated in Paniala, Paharpur, Chawdwan and Dhakki. The prominent varieties grown in the area are Dhakki, Shakri, Gulistan, Zaidi, Hillawi, Basra, Azadi and khudarawi. Dhakki Dates are well-known among all other varieties. Total area under dates cultivation in the district is 100,000 hectares, with total production of 11,000 tons dates. An average yield of Dhakki-Dates y-1 ranges from 6500 to 7000 tons i.e., 75% of the total production of dates in the area and dried dates production ranges from 800 - 1000 tons·year-1. A significant population is involved in processing of mazri and date palm leaves to prepare different products. Dates have a tremendous potential for economic uplift of the people. But growers face limitations and challenges regarding lack of information about customers and markets, harvesting, processing, and packaging techniques and infrastructure for producing good quality fresh dates. Fruit dropping in date palm particularly in Dhakki variety has become a serious concern. More than 70% date fruits drop before maturity. If production and processing constraints are properly handled, this may have significant socio-economic impact on local inhabitants.