Years Of Alfalfa Research Articles

Denitrification, leaching and immobilisation of applied 15N following legume and grass pastures in a semi-arid climate in Australia

Four consecutive 15N mass balance experiments lasting 18 months from February 1993 to August 1994 were carried out to assess the fate of applied 15N at 3 sites after 4 years of lucerne or snail medic and 20 years of Mitchell grass/naturalised medic pastures respectively in the Roma district of Queensland, Australia. 15N loss via denitrification was estimated from the difference between the recovery of applied Br(100kg Br/ha) and that of applied 15N(40kg N/ha) in the top 250mm at the end of each mass balance experiment. From February to August 1993, denitrification losses were 12–38% of applied 15N. N losses increased to 36–51% during August to November 1993, responding to the higher rainfall during this period. With even more rainfall during the period between November 1993 and March 1994, N losses were estimated to be 16–23%while displacement of 15N below 250 mm was 74–81%. When rainfall was much less between March 1994 and August 1994, N losses of only 15–19% of the applied 15N occurred at the 3 sites. It was found that although rainfall was the dominant factor controlling denitrification of the applied 15N, soil available carbon (C) (measured as water-soluble C) and the quantity of nitrate available were also important for soils already containing a considerable quantity of organic matter and N from residues of pasture legumes.

Comparative soil water, pasture production, and crop yields in phase farming systems with lucerne and annual pasture in Western Australia

Two field experiments in the Great Southern region of Western Australia compared the soil water content under lucerne (Medicago sativa) with subterranean clover (Trifolium subterranean) and annual medic (Medicago polymorpha) over a 2-year period. Lucerne depleted soil water (10–150 cm) between 40 and 100 mm at Borden and 20 and 60 mm at Pingrup compared with annual pasture. There was also less stored soil water after wheat (Triticum aestivum) and canola (Brassica napus) phases which followed the lucerne and annual pasture treatments, 30 and 48 mm after wheat, 49 and 29 mm after canola at Borden and Pingrup, respectively. Lucerne plant densities declined over 2 seasons from 35 to 25 plants/m2 (Borden) and from 56 to 42 plants/m2 (Pingrup), although it produced herbage quantities similar to or greater than clover/medic pastures. The lucerne pasture also had a reduced weed component. Wheat yield at Borden was higher after lucerne (4.7 t/ha) than after annual pasture (4.0 t/ha), whereas at Pingrup yields were similar (2 t/ha) but grain protein was higher (13.7% compared with 12.6%) . There was no yield response to applied nitrogen after lucerne or annual pasture at either site, but it increased grain protein at both sites. There was no pasture treatment effect on canola yield or oil content at Borden (2 t/ha, 46% oil). However, at Pingrup yield was higher (1.5 t/ha compared to 1.3 t/ha) and oil content was similar (41%) following lucerne–wheat. The results show that lucerne provides an opportunity to develop farming systems with greater water-use in the wheatbelt of Western Australia, and that at least 2 crops can be grown after 3 years of lucerne before soil water returns to the level found after annual pasture.

The nitrogen dynamics of 1-, 2- and 3-year stands of alfalfa in a cropping system

Alfalfa ( Medicago sativa L.) has long been recognized as a source of N for the subsequent crops in a rotation. However, the relationship between symbiotically fixed N and soil mineral N sources, and the way they are partitioned into harvested hay or incorporated biomass, is not well understood. Calculating N budgets (i.e. estimating N input and output in a system) is useful for increasing our understanding of N dynamics in agro-ecosystems. Field experiments were initiated to develop a basic N budget for 1–3-year-old stands of alfalfa in a crop rotation. Changes in total soil N were monitored and N 2 fixation was measured using the 15N isotope dilution technique. The total seasonal amount of N 2 fixed generally increased with each additional year of alfalfa, ranging from 174 kg N ha −1 for first year alfalfa to 466 kg N ha −1 for third year alfalfa. Alfalfa was also very effective at accessing deep-leached NO − 3 (i.e. soil NO − 3 greater than 1 m below the soil surface). The net soil N balance indicated that an average of 84, 148 and 137 kg N ha −1 was added to the soil system for 1-, 2- and 3-year-old alfalfa stands. The results of the budgeting process sugges that alfalfa stands as short as 2 years have the potential of making significant benefits to soil N status.

Interrupting Yield Depression in Monoculture Corn: Comparative Effectiveness of Grasses and Dicots

AbstractIt has been well documented that monoculture corn (Zea mays L.) yields less than corn grown in certain rotations. This field study conducted from 1992 through 1995 investigated several agronomic crops, rotated with corn, for their relative effectiveness in interrupting the yield depression associated with corn monoculture. The study was conducted on a Webster clay loam (fine‐loamy, mixed, mesic Typic Endoaquolls) near Lamberton, MN. Corn grain yields were increased by a single‐year interruption with either alfalfa (Medicago sativa L.) or sunflower (Helianthus annuus L.) for each of 4 yr, with the exception of sunflower in 1992. Averaged cross 4 yr, corn yields were increased from 7.81 Mg ha−4 for continuous corn by 19 and 17% following a single year of alfalfa and sunflower, respectively. A single year of sorghum [Sorghum bicolor (L.) Moench], sorghum × sudangrass (intraspecific S. bicolor hybrid), or fallow did not improve corn yields compared with corn monoculture. This was true for each year, and when averaged across 4 yr, with the exception of the corn‐fallow rotation in 1995. Averaged across 4 yr, a 2‐yr interruption with sunflower followed by alfalfa increased corn yield by 22%. A 2‐yr interruption of sorghum followed by sorghum × sudangrass increased corn yield by 6% over that of monoculture. We conclude that the closely related grasses were relatively ineffective rotation crops for corn. Leguminous alfalfa and nonleguminous sunflower were equally effective in alleviating the corn monoculture yield depression.

Residual nitrogen effects on wheat following legumes in the southern plains

Increasing nitrogen (N) fertilizer prices give rise to the question of N benefits from legumes in cropping systems in the Southern Great Plains. This study quantified wheat (Triticum aestivium L.) hay production and N uptake over seven years following six years of alfalfa (Medicago sativa L.), cicer milkvetch (Astragalus cicer L.), or grass (Old World bluestem, Bothriochloa ischaemum L.) production in western Oklahoma. Precipitation over the seven years averaged 550 mm·yr‐1. The major residual N effects were measured within the first five years. On a fine sandy loam soil, wheat hay yields averaged 3,070 kg·ha‐1·yr‐1 over five years following alfalfa, 2,580 kg·ha‐1·yr‐1 following milkvetch, and 950 kg·ha‐1·yr‐1 following grass with N uptake attributed to the residual effect from legumes (calculated by the difference method) averaged 34 kg N ha‐1·yr‐1 from alfalfa and 25 kg·ha‐1·yr‐1 from milkvetch. On a deep loamy sand soil, wheat hay yields averaged 1,290 kg·ha‐1·yr‐1 over five years following alfalfa and 710 kg·ha‐1·yr‐1 following grass with N uptake attributed to the residual effect from alfalfa averaged 8 kg N ha‐1·yr‐1. Thus, the residual N effect attributed to legumes was substantial on the fine sandy loam soil and relatively small on the deep loamy sand soil.

Fine root demography in alfalfa (Medicago sativa L.)

In perennial forages like alfalfa (Medicago sativa L.), repeated herbage removal may alter root production and mortality which, in turn, could affect deposition of fixed N in soil. Our objective was to determine the extent and patterns of fine-diameter root production and loss during the year of alfalfa stand establishment. The experiment was conducted on a loamy sand soil (Udorthentic Haploboroll) in Minnesota, USA, using horizontally installed minirhizotrons placed directly under the seeded rows at 10, 20, and 40 cm depths in four replicate blocks. We seeded four alfalfa germplasms that differed in N2 fixation capacity and root system architecture: Agate alfalfa, a winter hardy commercially-available cultivar; Ineffective Agate, which is a non-N2-fixing near isoline of Agate; a new germplasm that has few fibrous roots and strong tap-rooted traits; and a new germplasm that has many fibrous roots and a strongly branched root system architecture. Video images collected biweekly throughout the initial growing season were processed using C-MAP-ROOTS software. More than one-half of all fine roots in the upper 20 cm were produced during the first 7 weeks of growth. Root production was similar among germplasms, except that the highly fibrous, branch-rooted germplasm produced 29% more fine roots at 20 cm than other germplasms. In all germplasms, about 7% of the fine roots at each depth developed into secondarily thickened roots. By the end of the first growing season, greatest fine root mortality had occurred in the uppermost depth (48%), and least occurred at 40 cm (36%). Survival of contemporaneous root cohorts was not related to soil depth in a simple fashion, although all survivorship curves could be described using only five rates of exponential decline. There was a significant reduction in fine root mortality before the first herbage harvest, followed by a pronounced loss (average 22%) of fine roots at the 10- and 20-cm depths in the 2-week period following herbage removal. Median life spans of these early-season cohorts ranged from 58 to 131 days, based on fitted exponential equations. At all depths, fine roots produced in the 4 weeks before harvest (early- to mid-August) tended to have shorter median life spans than early-season cohorts. Similar patterns of fine root mortality did not occur at the second harvest. Germplasms differed in the pattern, but not the ultimate extent, of fine root mortality. Fine root turnover during the first year of alfalfa establishment in this experiment released an estimated 830 kg C ha−1 and 60 kg N ha−1, with no differences due to N2 fixation capacity or root system architecture.

The effect of C 360 tractor traffic over the soil in the third year of alfalfa ( Medicago varia Martin) cultivation

Passes of tractors and agricultural machines during the growing season take place not only over the loose soils but also over the untilled soils in the cultivation of perennial plants. The aim of the investigation, carried out at a depth of 0–30 cm on two soils (Orthic Luvisol developed from loess and Calcic Cambisol developed from chalk formations) was to determine the effect of one pass of a C 360 tractor of 2700 kg over the soil in the third year of alfalfa ( Medicago varia Martin) cultivation. The soil physical properties, e.g. bulk density, total porosity, air capacity and air permeability and morphological characteristics were evaluated. The passage of a tractor 3 t in weight did not cause any significant changes in the structure or air-water properties of the soils.

A Probability Method for Comparing Varieties against Checks

Combining results of tests conducted over a period of years is desirable when the tests are conducted at a single location or across locations known not to exhibit large nonrandom, predictable genotype ✕ location interactions. But when cumulative reports across tests are attempted, complications arise because of unbalanced structure. The objective of this work was to derive a method to compare varieties against checks using accumulated data in the usual situation, where varieties are changing over the years the accumulated tests are conducted. The resultant probability method is easy to use, easy to present in an extension publication, and easy to interpret by the extension audience. It tests the null hypothesis that a variety equals a check in performance and permits calculation of the probability that the variety equals a check in performance when the null hypothesis is rejected (type 1 error). Calculations are simplified data are coded and standardized for each test year. The method was used on an unbalanced data set yield of 23 varieties and 35 test years of alfalfa (Medicago sativa L.) grown near Ames, IA. Probability of one‐tailed Type I error anged from 0.47 to near 0.00 when data were coded on a test‐year mean basis, and from 0.86 to near 0.00 when data were coded on the basis of the mean of ‘Saranac’ and ‘Vernal’. The probability method determined that no more than seven test years were necessary to evaluate these varieties.

Manure and Mineral Fertilizer Effects in Continuous and Rotational Crop Sequences in Central New York1

AbstractEstimates of the effects of mineral fertilizer, manure, and legumes on crop yields and soil fertility in various technologies and environments are important for maintaining efficient crop production and reducing energy use in agriculture. Estimates of these effects were made in a long‐term study (1955 to 1968) at Aurora, N.Y. on soils of the Honeoye‐Lima and Kendaia series (Glossoboric Hapludalf and Aeric Haplaquept; fine loamy, mixed mesics; respectively). The crop sequences included continuous corn (Zea mays L.), wheat (Triticum aestivum L.), and grass and legume forage species, as well as several five‐phase rotations. The management treatments were manure (13.5 metric tons wet weight/ha/year averaged over the crop sequence), no manure, and different rates of N‐P‐K. The phases of each crop sequence were assigned to whole plots (0.0254 ha) in a randomized, complete‐block design (with six blocks or replicates), and the management treatments were assigned to the four sub‐plots.Two years of alfalfa (Medicago sativa L.) apparently contributed 135 kg N/ha to subsequent crops. Manure apparently supplied 5‐1‐4 kg N‐P‐K per metric ton (wet weight). The amounts of N available from manure, alfalfa, and mineral fertilizer were additive, at least on corn. A common N response curve over all cropping systems fit the corn data well, which suggests that manure and crop rotation only affected corn yields through their plant nutrient contributions. Soil organic matter and pH were maintained and extractable soil P and K were increased over the 14 years of the study in both continuous and rotational cropping systems (with or without manure). The results suggest that on these soils, the plant nutrient requirements of field crops can be completely supplied by legumes and manure, by mineral fertilizer, or by some combination of them without leading to decreases in soil fertility.

Effects of duration of grazed lucerne on long-term yields and nitrogen uptake of subsequent wheat

The long-term effects of varying durations of lucerne Icy, extended fallowing, and continuous wheat growing on the growth, yield, and nitrogen uptake of subsequent wheat crops were determined on two contrasting soils in northern New South Wales. Durations of lucerne ley were 3+, 2+ and 1+ years on a black earth and 5+, 3+ and 1+ years on a red-brown earth. With the exception of the first wheat crop, wheat production for several years following lucerne exceeded that following extended fallow or continuous wheat growing, whether measured as vegetative yield at anthesis, grain yield, nitrogen uptake, or grain protein. The beneficial effects of lucerne on vegetative yield, nitrogen uptake, and grain protein reached a maximum in the second crop after lucerne, and the effects of 2+ or more years of lucerne remained significant for the next five crops on the black earth and the next two crops on the red-brown earth. Grain yields fluctuated widely with season, the magnitude of the lucerne effect being much more dependent on rainfall, but the duration of the effect was similar for grain and vegetative parameters. The shorter duration of the lucerne effect on the red-brown earth appeared to be associated with its more freely draining nature and consequent loss of accumulated nitrogen. The optimum duration of lucerne for maintaining nitrogen-dependent wheat yields was 3+ years on both soil types. It eliminated the need for nitrogen fertilizer for the following five wheat crops on the black earth and three wheat crops on the red-brown earth. Extended fallowing also had a beneficial effect on all parameters, particularly in the first and second crops after the fallow ended. Its effect was generally significantly smaller than the lucerne effect except in the first crop after fallow.

Infiltration and Erosion as Affected by Minimum Tillage for Corn (Zea mays L.)

AbstractMinimum tillage for corn substantially increased infiltration and reduced soil erosion during a 5‐year study on a sloping, silt loam soil in Indiana. These results were obtained under high‐intensity, simulated rainfall with rows and tillage parallel to the slope. Infiltration averaged 24% greater and soil loss averaged 34% less from minimum tillage treatments than from conventional treatments. The different forms of minimum tillage tested, including plow‐plant (with and without a trailing harrow) and wheel‐track plant, resulted in about the same amount of erosion control. Erosion comparisons were made on first, third, and fifth year of corn following several years of alfalfa (medicago sativa) orchardgrass (dactylis glomerata) meadow. The relative erosion‐reducing effectiveness of minimum tillage as compared with conventional tillage declined from 44% to 34% to 27% during this period. Destruction of surface crusts by cultivation greatly reduced both soil and water losses throughout the remainder of the crop year. Soil aggregation, organic matter content, and porosity were slightly higher on minimum tillage plots than on conventional plots after 5 years of treatment. Three tons per acre of dry hay used as surface mulch applied after the first cultivation essentially eliminated soil and water losses during the remainder of the crop season. The mulch also effected major reductions in soil and water losses in the succeeding year.

EFFECT OF IRRIGATED CROP ROTATIONS ON YIELD AND SOIL FERTILITY

Crop yields and soil analyses were compared from three 4-year, two 5-year, and two 7-year rotations. The yields of potatoes from the seven rotations were not significantly different. Barley was grown in six rotations and the yields from these were not significantly different. The yield of sugar beets from the one rotation that did not receive any manure was significantly lower than those from the other six rotations. In the rotation in which sweet corn followed sweet clover green manure the yields were significantly lower than those from the other six rotations, where the corn followed sugar beets. This presumably was a result of the phytotoxicity of the decomposing clover. Good husbandry practices such as manure and fertilizer application evidently overshadow the effect of rotations on the yields of irrigated crops. The organic matter and nitrogen of the surface 6 in. of soil were maintained in the rotations that included 3 years of alfalfa or alfalfa–brome mixture. These soil constituents were not maintained with a single year of alfalfa or with a partial green manure crop.

Influence of Past Soil Treatment on Yield, Composition, and Fertilizer Phosphorus Utilization by Alfalfa1

Phosphorus fertilizer was used at five rates on established stands of alfalfa on irrigated Tripp very fine sandy loam in western Nebraska. One rate of phosphorus fertilizer was tagged with P32. Two 6-year rotations which included 3 years of alfalfa were used, one of which had received 12 tons of barnyard manure per acre per rotation cycle since 1912. Total phosphorus, Nitrogen, and cation concentrations; fertilizer phosphorus concentration for the tagged treatment; and yields of alfalfa were measured for 2 years. Residual effects of first-year fertilizer applications were measured through the use of second applications of tagged phosphorus fertilizer. All rates of phosphorus fertilizer increased the yield of alfalfa on the non-manured rotation while only the 160-pound P2O5 per acre rate caused a significant increase in yield on the manured rotation. The long-time use of manure increased the yield and phosphorus concentration of alfalfa. Phosphorus concentration in the alfalfa increased with increasing rates of phosphorus fertilization and decreased with plant maturity. The long-time use of manure and the prior use of phosphorus fertilizer decreased the relative uptake of applied fertilizer phosphorus. Application of phosphorus fertilizer had little effect on concentration of either nitrogen or cations in alfalfa.

Water‐Stability of Aggregates from Potato Plots as Affected by Different Rotation Systems Under Irrigation in Western Nebraska

AbstractA series of crop rotation plots under irrigation were established in 1912 on Tripp very fine sandy loam. From the series of rotations the following potato plots were selected for the study of water‐stability of aggregates: (i) continuous cropping of potatoes, (ii) 3‐year rotation (potatoes, oats or barley, sugar beets), and (iii) 6‐year rotation (3 years of alfalfa, potatoes, oats or barley, sugar beets). Neither manure nor fertilizer was added to these irrigated plots during the 39 years of the experiment.The soil from the surface 2 inches of the potato plots was sampled and separated into 13 size fractions by means of rotary sieves. The resistance of aggregates in each size fraction to dispersion in water was obtained by shaking the aggregates in water for 2 and 2,000 minutes. The size distribution of aggregates in water was determined by means of sieves, elutriators, gravity and centrifugal sedimentation. The degree of aggregation of soil particles is expressed by the ratio: urn:x-wiley:03615995:saj2sssaj195403615995001800030004x:equation:saj2sssaj195403615995001800030004x-math-0001 The size distribution of aggregates in water prior to any dispersion treatment is taken as that obtained by dry aggregate analysis, providing the aggregates are wetted either under partial vacuum or by capillarity. The ratios of geometric mean diameter for aggregates in water prior to shaking were 16, 10 and 31 for the continuous cropping, 3‐year rotation, and 6‐year rotation, respectively. Shaking the aggregates in water for 2 minutes produced a marked decrease in the ratios for the three plots: 1.79, 1.97, and 3.21. The marked decrease in the ratios in the 2‐minute shaking period indicates the instability of large‐diameter aggregates in water. The plot with alfalfa in the rotation showed a pronounced effect on the aggregation of soil particles as compared to the plots without alfalfa. Even after 2,000 minutes of shaking the aggregates in water, the plot with alfalfa showed a high degree of aggregation of soil particles. Highly significant regression coefficients were obtained with aggregation and clay content or total nitrogen content or apparent density of air‐dried aggregate or 15‐atmosphere tension values.