Weed control in rice is challenging, particularly in light of increased resistance to herbicides in weed populations and diminishing availability of irrigation water. Certain indica rice cultivars can produce high yields and suppress weeds in conventional flood-irrigated, drill-seeded systems in the southern United States under reduced herbicide inputs, but their response to reduced irrigation inputs in these systems in not known. Rice productivity and weed control by weed-suppressive cultivars and conventional nonsuppressive cultivars were evaluated in a nonflooded furrow-irrigated (FU) system and a conventionally flooded (FL) system under three levels of weed management (herbicide inputs) in a 3-yr field study. Rice yields across all weed management levels yielded ∼ 76% less in the FU system than in the FL system. The allelopathic indica cultivar, ‘PI 312777’, and commercial hybrid rice ‘CLXL729’ generally produced the highest grain yields and greatest suppression of barnyardgrass in both irrigation systems. ‘Bengal’ and ‘Wells’ were the top-yielding conventional cultivars whereas ‘Lemont’ and ‘CL171AR’ yielded the least. Weed suppression by PI 312777 and CLXL729 under “medium” weed management was equivalent to that of Lemont and CL171AR at the “high” management level, suggesting that the weed-suppressive cultivars may be able to compensate for suboptimal herbicide inputs or incomplete weed control.
Precision farming, or site-specific farming, has emerged as a promising group of technologies that could increase agricultural productivity with environmental stewardship. It is a knowledge-based system that integrates many advanced information technologies. Precision farming enables farmers to apply precise amounts of fertilizers, pesticides, water, seeds or other inputs to specific areas where and when they are needed for optimal crop growth. The major components include grid sampling, Global Positioning System (GPS), geographic information systems (GIS), remote sensing, yield monitors, variable rate application (VRA), and computer simulation models. This paper reviews the current state of the art of precision farming and its major components, and discusses economic feasibility and potential implications for agricultural structure and rural communities.
This paper evaluates the profitability and economic risks associated with four cropping systems for the Sustainable Agriculture Demonstration site at Beltsville, Maryland, for the 1994-97 period. Each system follows a 2-year rotation of corn in the first year and winter wheat and soybean in the second year. The four systems are (1) a no-tillage system with recommended fertilizer and herbicide inputs, (2) a no-tillage system with crownvetch living mulch, (3) a no-tillage system with winter annual cover crop, and (4) a reduced tillage manurebased system without chemical inputs. The cover crop system is the most profitable ($238 in gross margin), closely followed by the no-tillage ($233) and the manure-based system ($217). Even though farmers desire a cropping system that maximizes profits, the variability of profits, or risks, can influence the desirability of the cropping system. In terms of risks, no-tillage is the most preferred rotation with the smallest coefficient of variation (1.14) followed by the cover crop system (1.24), the manure-based system (1.58), and the crownvetch system (5.45). The same ranking can be obtained using a ''safety-first'' criterion for risk-averse farmers, in which the gross margin of the no-tillage system would exceed $53 ha 1 in three out of four years, while the gross margin of the cover crop system would exceed $39 ha 1 in three out of four years. The manure-based system is an organic system and it was not profitable in 1996 and 1997 because of weed infestations. However, the manure-based system shows potential to be the most profitable if some methods can be found to control weeds without resorting
Sustainable production systems are needed to maintain soil resources and reduce environmental contamination on erodible lands that are incompatible with tillageintensive operations. A long-term cropping systems comparison was established at Beltsville, Maryland, on a site with 2 to 15% slope to evaluate the efficacy of sustainable strategies compatible with reduced-tillage systems. All systems followed a 2-year rotation of corn the first year and winter wheat followed by soybean the second year. Treatments included (1) no-tillage system with recommended fertilizer and herbicide inputs, (2) crownvetch living mulch system with similar inputs to the no-tillage system, (3) cover crop system including a hairy vetch cover crop before corn and a wheat cover crop before soybean with reduced fertilizer and herbicide inputs, and (4) manure system including crimson clover green manure plus cow manure for nutrient sources, chisel plow/disk for incorporating manure, and rotary hoe plus cultivation for weed control. Results from the initial 4 years demonstrated the relative productivity of these systems. Corn yields were similar in the no-tillage and cover crop systems in each year; both systems averaged 7.8 Mg ha~l compared to 5.7 Mg ha~x in both the crownvetch and manure systems. Wheat yields were highest in the manure system in the first 2 years and in the crownvetch system in the last 2 years. Soybean yields were highest in the cover crop system in all years. The manure system usually had lower yields than the highest yielding systems, partly because of competition from uncontrolled weeds. Several measures of the efficiency of grain production were evaluated. The no-tillage system produced the most grain per total vegetative biomass throughout the rotation. The cover crop system produced the most grain per unit of external nitrogen input and, along with the no-tillage system, had the highest corn water-use efficiency. The cover crop system also recycled the most vegetative residues and nutrients of all systems. No single system performed best according to all measures of comparison, suggesting that trade-offs will be required when choosing production systems.
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