For thousands of years, agriculture and tillage were considered synonymous. It was simply not thought possible to grow crops without first tilling the soil before planting and for weed control. The advent of modern herbicides permitted no‐tillage (NT) to be developed and practiced on actual working family farms. No‐tillage is generally defined as planting crops in unprepared soil with at least 30% mulch cover. Adoption of NT after its successful demonstration in the 1950s was slow. However, with better planters, herbicides, and accumulated experience, NT began to be widely adopted in the 1980s in the United States and then in Australia, South America, and Canada. Today, approximately 23% of the total cropland in the United States is planted using NT. No‐tillage has revolutionized agricultural systems because it allows individual producers to manage greater amounts of land with reduced energy, labor, and machinery inputs. At the same time, NT is a very effective erosion control measure and improves water and fertilizer use efficiency so that many crops yield better under NT than under tilled systems. Tillage, like crops, can be rotated but the benefits of NT are most likely to be realized with continuous application. We review some of the early work that led to the development of NT and how NT impacts the crop, soil, hydrology, and farm economics. While highly sustainable, there are still many challenges that remain for researchers to solve so the benefits of NT can be realized on expanded land area and for more crops, worldwide.
Dicamba (3,6‐dichloro‐2‐methoxybenzoic acid) effectively controls many dicotyledonous weeds, but nontarget species such as soybean [Glycine max (L.) Merrill) are susceptible to spray or vapor drift. Field studies were conducted on a Canfield silt loam (fineloamy, mixed, mesic Aquic Fragiudalf) soil to determine the response of ‘Elf’ and ‘Williams’ soybean to dicamba over a wide range of applied rates, and to evaluate the use of dicamba injury symptoms to predict yield reductions. Soybean yield in response to increasing rates of dicamba was described by equations of the form y = Aexp( −bx), where y = yield, A = maximum yield (rate = 0 g ha−1), b is a constant, and x = rate of dicamba applied. Height reduction, seed number ha−1, and morphological symptoms of dicamba injury were useful in assessing yield reduction. Except for Elf soybean treated at the midbloom stage, there was no yield reduction without height reduction, regardless of foliar symptoms. Seed number ha−1 decreased with increasing rates of dicamba and was closely correlated with yield. Yield reductions greater than 10% were indicated by severe morphological symptoms of injury, such as terminal bud kill, splitting of the stem, swollen petioles, and curled, malformed pods. Other foliar symptoms, such as distinctive crinkling and cupping of the terminal leaves, occurred at rates much lower than those required to cause yield reductions.
Glyphosate (N‐[phosphonomethyl]glycine)3 formulated as Round‐up® herbicide,4 was applied on 0.3‐ to 3.1‐ha watersheds at rates of 1.10‐, 3.36‐, and 8.96‐kg/ha as a preseeding herbicide in the no‐tillage establishment of rescue (Festuca arundinacea L.) and corn (Zea mays L.). Runoff from natural rainfall following early springtime treatments was measured and analyzed to define concentration and transport of glyphosate under these conditions.The highest concentration of glyphosate (5.2 mg/liter) was found in runoff occurring 1 day after treatment at the highest rate. Glyphosate (2 µg/liter) was detected in runoff from this watershed up to 4 months after treatment. For the lower application rates, maximum concentration of the herbicide in runoff was < 100 µg/liter for events occurring 9–10 days after application and decreased to <2 µg/liter within 2 months of treatment. The maximum amount of glyphosate transport by runoff was 1.85% of the amount applied, most of which occurred during a single storm on the day after application. In each of the three study years, herbicide transport in the first runoff event following treatment accounted for 99% of the total runoff transport on one watershed. Glyphosate residues in the upper 2.5 cm of treated soil decreased logarithmically with the logarithm of time; they persisted several weeks longer than in the runoff water.
Corn (Zea mays L.) was grown continuously without tillage (no-tillage) and with conventional tillage for 7 years to evaluate several herbicides for use in both crop culture systems. The only consistently satisfactory herbicide combinations for the no-tillage corn were 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) and 1,1′-dimethyl-4,4′bipyridinium ion (paraquat) or 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), simazine, and paraquat. Annual weed population shifted rapidly with different herbicide systems; fall panicum (Panicum dichotomiflorum Michx.) was the major annual weed where triazines were used as the residual herbicide. After several years of corn grown with no-tillage, hempdogbane (Apocynum cannabinum L.) became a significant problem in some plots. Corn yields with no-tillage were equal to yields in tilled areas provided weed control was satisfactory.
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