Ronald E. Phillips

No-Tillage Agriculture

The no-tillage cropping system, a combination of ancient and modern agricultural practices, has been rapidly increasing in use. By the year 2000, as much as 65 percent of the acreage of crops grown in the United States may be grown by the no-tillage practice. Soil erosion, the major source of pollutants in rural streams, is virtually eliminated when no-tillage agriculture is practiced. The no-tillage system reduces the energy input into corn and soybean production by 7 and 18 percent, respectively, when compared to the conventional tillage system of moldboard plowing followed by disking. In addition, crop yields are as high as or higher than those obtained with traditional tillage practices on large areas of agricultural land.

New Developments and Perspectives on Soil Potassium Quantity/Intensity Relationships

Publisher Summary The purpose of this chapter is to discuss the Quality/Intensity concept in relation to modern cation exchange theory on binary and ternary soil systems, to introduce the concepts involving the theory and application of ion-selective electrodes to rapid estimations of Q/I parameters for soil suspensions, and to discuss the future application of the Q/I concept in predicting soil K availability vis-a-vis plants. The chapter discusses the triple layer model (TLM). Advances in ion-selective electrode (ISE) technology have resulted in the development of potentiometric methods of determining K + in soil extracts and suspensions. Advantages provided by ISEs include simple, nondestructive analyses; direct measurements of ion activities or concentrations; automated analyses; continuous monitoring capabilities; and in situ determinations of ions. These unique advantages of ISE can lead to a new way of characterizing the various forms and reactions of K in soils and minerals. Q/I plays a fundamental role in understanding K availability to plants, an additional purpose is its use in the environmentally sound management of fertilizers, involving soil surface-solution interactive components. These components determine soil solution composition and thus the potential fate of plant nutrients—for example, leaching, uptake, and transformations. The ultimate future application of Q/I, as computing power becomes less costly and understanding soils and plant root systems as polycationic systems advances, would be in modeling soil–plant systems on a real-time basis.

Impact of Soil Management Practices on Nitrogen Leaching

ABSTRACT Soil management practices have an important influence upon N leaching. These practices include tillage, which may vary from region to region in the united States. The influence of tillage upon the soil water regime is discussed, including the effects upon evaporation from soil surfaces, paths of water flow, and pore size distribution. Nitrate leaching is considered as a function, first of soil water behavior and second of the abundance and distribution of nitrate in the soil. Amounts and forms of N in the soil are influenced by N transformations (nitrification, denitrification, and mineralization-immobilization). Soil management of water (including irrigation, drainage, and winter cropping) are also important in influencing nitrate leaching.

THE TRANSIENT INSTABILITY OF TENSIOMETER READINGS DURING INFILTRATION

Tensiometer readings were taken before, just after, 30 minutes after, and 24 h after an irrigation of 50 mm applied in 90 minutes. Readings before and 24 h after irrigation were normal and stable. Readings taken just after and 30 minutes after irrigation showed variable behavior. At some depths there were changes from negative to positive pressure and at one depth the reverse occurred. At several depths practically no change was observed with time. Soil samples taken before, just after, and 24 h after irrigation showed that 13.5 mm of H2O could be accounted for immediately after irrigation ceased in the 0− to 60-cm depth, but that none could be accounted for 24 h later. Presumably all of it had moved deeper than 60 cm in 24 h. The results suggest that earlier researchers have merely waited to take tensiometer readings until the values stabilized, which missed most of the infiltration. The results also demonstrate the importance of macro-pore flow during infiltration of water. The variable pattern of tensiometer response is ascribed to the random intersection of tensiometer cups by macropores.

Effects of Climate on Performance of No-Tillage

Distribution and amount of rainfall and temperature have more direct effects upon performance of no-tillage row crops in dryland agriculture than any other climatic factors. As will be pointed out in Chapter 4, the distribution of rainfall during the growing season is very important to the maximum conservation of soil water due to no-tillage or a mulch. The more rainfall events which occur during the growing season, the greater the difference of soil water evaporation between no-tillage or a mulch and conventional tillage; therefore, the more soil water will be conserved from the no-tillage than from conventional tillage which is then available for transpiration through plants. In central Kentucky the ideal distribution and amount of rainfall to obtain near maximum conservation is about 2.5–3.0 cm of rain per week, a month prior to planting until the crop reaches full canopy, about mid-July (see Table 4-1). From Table 4-1, it can be seen that the average water use, soil water evaporation plus transpiration, by corn for the 1970, 1971, and 1972 and 1973 growing seasons (May through September) on the conventional tillage treatment were 35.5, 51.4, 35.5 and 50.6 cm, respectively. The grain yields were 6,136, 10,841, 10,841 and 8,795 for 1970, 1971, 1972 and 1973, respectively. The water use in 1970 and 1972 was the same, 35.5 cm, while grain yields were drastically different, 6,136 and 10,841 kg/ha.