Abstract Relying more on biological N 2 fixation has been suggested as a way to meet one of the major challenges of agricultural sustainability. A 15 N study was conducted to compare the fate of applied legume and fertilizer N in a long‐term cropping systems experiment. Nitrogen‐15–1abeled red clover ( Trifolium pratense L.) and (NH 4 ) 2 SO 4 were applied to microplots within the low‐input and conventional cropping systems of the Farming Systems Trial at the Rodale Institute Research Center in Pennsylvania. The 15 N was applied to soil and traced into corn ( Zea mays L.) in 1987 and 1988. Residual 15 N was also traced into second‐year spring barley ( Hordeum vulgare L.). Legume and fertilizer 15 N remaining in soil was measured and loss of N was calculated by difference. More fertilizer than legume N was recovered by crops (40 vs. 17% of input), more legume than fertilizer N was retained in soil (47 vs. 17% of input), and similar amounts of N from both sources were lost from the cropping systems (39% of input) over the 2‐yr period. More fertilizer than legume N was lost during the year of application (38 vs. 18% of input), but more legume than fertilizer N was lost the year after application (17 vs. 4% of input). Residual fertilizer and legume 15 N was distributed similarly among soil fractions. Soil microbial biomass was larger in the legume‐based system. A larger, but not necessarily more active, soil microbial biomass was probably responsible for the greater soil N supplying capacity in the legume‐based compared with fertilizer‐based system.
Abstract Extract Kikuyu grass (Petinisetum clandestinum) was introduced to New Zealand from Rhodesia in 1920. Since then it has spread widely in Northland and South Auckland, and has also become established further south, mainly on sandy soils in coastal, frost-free areas.
Management-induced changes in soil carbon (C) and nitrogen contents were difficult to document in these soils because much of the observed difference in soil organic matter (SOM) levels was due to the heterogeneity of texture and drainage characteristics. The kinds and amounts of soil amendments applied and plant residues returned impact SOM and related characteristics by their effect on microorganisms, on the supply of plant-available nutrients, and on soil structure. The amount of C translocated to the roots of each plant species in a crop rotation and the structure of these root systems could be the most important factor affecting SOM dynamics. An integral component of a sustainable agroecosystem is the presence of a continual supply of SOM to provide substrate for an active, healthy soil biological community, an environment for vigorous plant-root development which resists soil erosion, and adequate nutrients for plant growth.
Farmer interest in conservation tillage (CT) has increased with rising fuel prices, the newConservation Security Program, and desire for improved resource stewardship. Research has shown thatfarmers see maximum benefit to CT if it is part of a cropping system that includes cover crops and croprotation. The CT system best suited for a particular operation will vary with the crop, site, soils, and otherfactors. Many county extension agents in Georgia indicated they needed further training to meet theinformational needs of their farmers. Consequently, the University of Georgia College of Agricultural andEnvironmental Sciences created a multi-disciplinary conservation tillage educational task force to develop atraining program. The College recognized the need for input from other agencies that had extensiveexperience in conservation and management of natural resources. The task force includes UGA-CAES faculty,USDA-NRCS personnel, USDA-ARS research scientists, and non-governmental representatives. A survey ofthe county agents was conducted to determine specific training needs and attitudes towards CT. The surveyindicated most county agents had a positive attitude towards CT systems, but their knowledge was weak onthe differences between CT systems and conventional systems in terms of: inputs, equipment, changes in soilquality and fertility, effects on yields and quality of different commodities, and specifics on how to implement CTpractices. The survey also indicated that more information on the economics of CT systems was needed.Agents preferred a combination of classroom and field training. The results of the survey were used to developspecific training modules with the purpose of improving the knowledge level of county agents on conservationtillage systems.
Introduction Canola is an agronomic crop grown in many countries for production of vegetable oil and meal. Demand for canola oil continues to increase worldwide. People consume canola oil and consider it to be a healthy oil with low levels of saturated fats. More recently, there also is intense interest in using canola oil to produce biodiesel to replace diesel fuel. Canola meal is normally fed to poultry and livestock as a source of protein.
ABSTRACT Calcium (Ca) availability in the 0 to 8 cm soil depth often limits peanut yield and influences grade in the southeastern United States. Field experiments were conducted in 2012 and 2013 at the University of Georgia's Coastal Plain Experiment Station, Tifton, GA (CPES) and the Southwest Georgia Research and Education Center, Plains, GA (SWREC) to determine large-seeded (Georgia-06G) and medium-seed sized (Georgia Greener) runner-type cultivar response to gypsum application rates of 0, 560, 1120, 1650 kg/ha. Peanut pod yield and grade (TSMK) were significantly different between locations with 7610 and 6540 kg/ha at CPES and SWREC, respectively. However, there were no differences between peanut cultivars or gypsum rates. Standard germination, seed vigor (cold germination), and seed Ca content analysis were also conducted on subsamples from each plot. Average peanut seed germination was 97% across all samples. No differences were observed for standard germination or vigor testing. Differences in locations were observed for yield, TSMK, percent jumbo, percent medium kernels, and seed Ca content. Peanut cultivar and gypsum application rate had effects on seed Ca concentration. Seed Ca concentration levels were 825 and 787 mg/kg for Georgia Greener and Georgia-06G, respectively. Seed Ca content increased as field gypsum application rate increased at both locations.
