Tillage

The practice of tillage dates back to the beginning of history, and was well-established in Mesopotamia at least as early as about 2000 B.C. (see Chapter 1). Frequent reference is made to the practice in both the Old and New Testaments. 

Anyone who attempts to discuss tillage is considerably handicapped by the lack of an exact, narrow definition of the term, and by a variation in usage of this and related terms in different communities. According to Webster s Dictionary to till means to turn or stir (as by plowing, harrowing, or hoeing) and prepare for seed to sow, dress, and raise crops from and to cultivate. By this definition the terms till, plow, cultivate, and even seed are nearly synonyms. 

In problem soils the preparation for a crop may involve improvements in the physical condition of the deeper layers of the soil. This commonly occurs in soils that have poor drainage, especially if they have been tilled previously when they were too wet. The 

Thorough cultivation of crops vvas for centuries accepted as a very essential step in the production of high yields. This was attributed largely to the improvement of the physical condition of the soil. In recent years this idea has been largely discredited. Improved physical condition of the soil, if it occurs, is now recognized as likely to be one of the lesser benefits. 

Animal manures are also usually most effective when incorporated into the soil if conservation of the nutrients is the primary aim. Discing into the soil immediately after application is usually the most effective practice. This provides for good contact and mixing at a depth sufficient for capillarity in the soil to maintain good moisture conditions and rapid nitrification. Under many conditions it is often easier to broadcast the manure on the unplowed field and turn it under. This is a fairly satisfactory procedure provided that the manure is exposed to the weather for only a short period, and provided 

---

Fertilizer Use. The worldwide use of fertilizers has an important, positive effect on the environment. Conservative estimates (112) iadicate that about 30% of world food production is direcdy attributable to fertilizer use. Without fertilizer, therefore, at least 30% mote virgin land would have to be devoted to agriculture, and 30% more labor and other resources would have to be expended. Even more serious would be the effects of land tillage and cropping without nutrient replenishment. Past experience has shown that, under such a condition, crop yields progressively decrease, the land eventually becomes barren, and forces of wiad and water erosion prevail. 

Many factors affect the mechanisms and kinetics of sorption and transport processes. For instance, differences in the chemical stmcture and properties, ie, ionizahility, solubiUty in water, vapor pressure, and polarity, between pesticides affect their behavior in the environment through effects on sorption and transport processes. Differences in soil properties, ie, pH and percentage of organic carbon and clay contents, and soil conditions, ie, moisture content and landscape position climatic conditions, ie, temperature, precipitation, and radiation and cultural practices, ie, crop and tillage, can all modify the behavior of the pesticide in soils. Persistence of a pesticide in soil is a consequence of a complex interaction of processes. Because the persistence of a pesticide can govern its availabiUty and efficacy for pest control, as weU as its potential for adverse environmental impacts, knowledge of the basic processes is necessary if the benefits of the pesticide ate to be maximized. 

Conservation tillage increased atra2ine and metolachlor surface mnoff by 42% and decreased tile discharge by 15% compared with conventional tillage, but total field mnoff was the same from all treatments (53). Runoff events shordy after herbicide appHcation produced the greatest herbicide concentrations and losses in both surface mnoff and subsurface drainage. 

The interaction of all these factors makes it difficult to predict an overall effect of conservation tillage on the potential leaching of a pesticide compared to that in a conventionally tilled field. However, it was found that a prolonged rain immediately after appHcation resulted in short-term levels of pesticide in groundwater to be greater under no-tiU than under conventional till plots, which suggested that preferential transport in no-tiU had occurred... 

In contrast, it was suggested that there can be greater leaching losses of surface-appHed pesticides to groundwater under plow-tillage than under no-tiU... 

The estimates in Table 3 represent one inventory however, a further estimate of uncertainties may be found by comparing other recent ongoing inventories for the UK. Pain et alJ have very recently estimated UK emissions from livestock production systems (including tillage crops) at 240 Gg NHj yr while ApSimon et al. (personal communication) estimate a figure of around 280 Gg NHj yr h Including the non-agriciiltiiral sources at around 40 Gg NHj yr the official estimate recently adopted by the Department of the Environment is 320 Gg NHj yr h If these estimates are contrasted with the other recent estimate of UK... 

Monsanto Patents. A process for HIPS is described in the patent issued to Carter and Simon (35)and is illustrated in Fig. 20. There are two reactors an anchor agitated CSTR and a reflux cooled LFR. Both reactors can be operated at variable and controllable tillage so that a given product can be made over a range of rates. 

In a typical example (33) a fresh feed of 8% polybutadiene rubber in styrene is added with antioxidant, mineral oil, and recycled monomer to the first reactor at 145 lbs./hr. The reactor is a 100-gallon kettle at approximately 50% tillage with the anchor rotating at 65 rpm. The contents are held at 124°C and about 18% conversion. Cooling is effected via the sensible heat of the feed stream and heat transfer to the reactor jacket. In this reactor the rubber phase particles are formed, their average size determined and much of their morphology established. Particle size is controlled to a large measure by the anchor rpm. 

Most biological and cultural pest controls return greater profits than pesticides. For example, biological pest controls are reported to return from 30 to 300 per dollar invested in control (16). Various cultural controls like host plant resistance, crop rotations, and tillage, also return 30 to 300 per dollar Invested in pest control (16). 

Baker, J. M., Ochsner, T. E., Venterea, R. T., and Griffis, T. J. (2007). Tillage and soil carbon sequestration—What do we really know Commentary. Agric. Ecosyst. Environ. 118,1-5. 

Blanco-Canqui, H. and Lai, R. (2008). No-tillage and soil-profile carbon sequestration An on-farm assessment Soil Sci. Soc. Am. J. 72, 693-701. 

Mishra, U., Ussiri, D. A. N., and Lai, R. (2010). Tillage effects on soil organic carbon storage and dynamics in Corn Belt of Ohio USA. Soil Tillage Res. 107, 88-96. 

West, T. O. and Post, W. M. (2002). Soil organic carbon sequestration rates by tillage and crop rotation. A global data analysis. Soil Sci. Soc. Am. J. 66,1930-1946. 

O2 availability, water content. Structural - soil type, porosity, clay content, fertility. Agricultural - Fertilizer addition, herbicide pesticide application, tillage, cropping systems etc. 

P. A. Harris, H. H. Schomberg, P. A. Banks, and J. Giddens, Burning, tillage and herbicide effects on the soil microflora in a wheat-soybean double-crop system. Soil Biology and Biochemistry 27 153 (1995). 

N. Z. Lupwayi, W. A. Rice, and G. W. Clayton, Soil microbial diversity and community structure under wheat as influenced by tillage and crop rotation. Soil Biol. Biochem. 30 1733 (1998). 

Tillage Sorghum (Sorghum bicolor), soybean (Glycine 95... 

---