Changes in infiltration under alfalfa as influenced by time and wheel traffic

Infiltration rates were measured for alfalfa, (Medicago saliva L., cv. WL514) subjected to treatments where wheel traffic was varied in terms of area covered and time of application on a Wasco sandy loam (coarse-loamy, mixed, nonacid thermic Xeric Torriorthent). Traffic treatments were (i) No-traffic, (ii) Preplant, (iii) Repeated, and (iv) traffic similar to what a grower would apply. Infiltration rates increased for all treatments, with increases being 240% for treatments without harvest traffic and 140% for treatments with harvest traffic Increases in infiltration were related to decreases in stand density. Slight packing (traffic) applied before the soil was flood-irrigated in 1983 increased infiltration rates 20% compared to flooding loosened soil (no traffic). Harvest traffic resulted in slower water movement in the soil

Bulk density of a sandy loam: traffic, tillage, and irrigation method effects

Modern crop production creates a cycle between soil compaction caused by traffic and alleviation of this condition by tillage or natural processes such as freezing and thawing. The objective of this study was to evaluate important management practices as they relate to changes in bulk density of a tilled sandy loam soil. Practices evaluated were irrigation method, time between tillage and traffic, tire pressure and wheel load of applied traffic, and controlled traffic. Relationships among bulk density, penetration resistance, and infiltration rate were determined. Experiments were conducted in the San Joaquin Valley of California, on a sandy loam soil (Entisol) with an organic-matter content of <1%. After tillage, settling and trafficking of a soil resulted in rapid changes in its bulk density until a new equilibrium was reached. Tire pressure of 408 kPa and wheel weight of 2724 kg applied at moisture contents near field capacity resulted in a bulk density of 1.92 Mg m-3 , compared with a value of 1.67 for no traffic. The time interval between tillage and traffic did not affect final bulk density. Drip irrigation, which did not saturate the soil, resulted in a bulk density of ?0.1 Mg m-3 lower than flood irrigation, which saturated the soil surface. Wheel traffic in the furrow resulted in only small changes in the bulk density within the row. When tillage did not occur between cropping seasons, traffic caused high bulk densities in the furrow but only small changes in the row. An increase in bulk density from 1.7 to 1.89 Mg m-3 decreased the infiltration rate by four times and increased resistance to penetration at the end of the season by three times. Knowledge of how management practices affect bulk density can aid growers in reducing recompaction following tillage

Fine root development of alfalfa as affected by wheel traffic

Root development in alfalfa (Medicago satire L.) is dependent of many factors including the soil environment which is influenced by crop management procedures. Soil compaction, which is unavoidable under current management procedures, can have a detrimental effect on root development. The purpose of this field experiment was to compare the effects of controlled and conventional traffic management on alfalfa fine root growth in a Wasco sandy loam (coarse-loamy, mixed, nonacid thermic Typic Torriorthent). No wheel traffic and traffic only before planting were compared to two conventional systems that varied in the amount of traffic applied during crop production. Twenty months after planting, there was a significant decrease in fine root density (FRD) from single passes of traffic after each harvest down to a 0.45-m depth while several passes after each harvest significantly decreased FRD down to 1.8-m depth. Regardless of treatment, root density was greatest in the upper 0.1 m of soil decreasing to 1.8 m in the first summer. By the second summer FRD showed bimodal distribution with significantly fewer roots at 0.3 to 0.6 m compared to layers above and below this depth. Seasonally there was a significantly higher root density during the winter than the summer in the upper 0.3 m of soil. The results of this study shows that alfalfa fine roots more thoroughly exploit the soil volume in the absence of wheel traffic and that compaction from traffic diminished root growth to different depths depending on its intensity

Alfalfa (Medicago sativa L.) water use efficiency as affected by harvest traffic and soil compaction in a sandy loam soil

Traffic during alfalfa harvest operations can cause soil compaction and damage to newly growing stems. Root exploration for soil water and nutrients, forage growth dynamics, and final yield can all be affected. The objectives of this study were to determine the long-term effects of harvest traffic and soil compaction on water-use efficiency (WUE) of alfalfa grown in a Wasco sandy loam (coarse-loamy, mixed, nonacid, thermic Typic Torriorthents). Alfalfa was planted into tilled soil and managed with or without harvest traffic. Plants subjected to traffic during harvest had a significantly lower WUE two out of the three years studied compared to plants that were never subject to traffic. The second experiment examined whether planting alfalfa into compacted soil and managed with or without harvest traffic altered WUE. Soil compaction had no affect on alfalfa WUE. It was significantly lower when grown in compacted soil and subjected to harvest traffic. It is suggested that the decrease in WUE caused by harvest traffic may be explained by plants allocating carbohydrates to damaged shoots and crowns instead of to above ground forage production. The area of the field affected by harvest traffic, which damages newly growing stems, should be minimized to increase crop water use efficiency

Alfalfa yield as affected by harvest traffic and soil compaction in a sandy loam soil

Harvesting alfalfa (Medicago saliva L.) results in plants being subjected to traffic at different times during the growth cycle with equipment having different wheel sizes and loads. The affect of this traffic could have important ramifications on yield. The objectives of this study were to determine the long-term effects of harvest traffic and soil compaction on alfalfa yield. In the first experiment, two conventional traffic systems were compared to alfalfa production with no traffic. A single traffic event, that covered 100% of the plot area 3 to 5 d after each swathing, compared to no traffic significantly decreased yield by 20% in the 1st yr, 16.5% in the 2nd yr, 14% in the 3rd yr, with no significant difference the 4th yr. There was no difference in total yield between nontrafficked and a typical grower's traffic pattern the 1st yr, but in the succeeding 3 yr there was a 5 to 17% reduction. The effects of soil compaction and harvest traffic on yield were separated in the second experiment. Alfalfa grown in moderately and heavily compacted soil had a 12 and 26% decrease respectively in seasonal total yield compared to the yield from plants grown in noncompacted soil the 1st yr. Annual yields were the same regardless of the degree of soil compaction in the 3rd yr. When harvest traffic was applied to alfalfa grown in extremely compacted soil there was an additional decrease in yield. It was not statistically significant the 1st yr, but in the following 2 yr, 1987 and 1988, yield was significantly reduced by 17.8 and 19.1%, respectively. Alfalfa yields were significantly reduced both by harvest traffic and compacted soil. To achieve optimum long-term alfalfa yields compacted soil must be tilled before planting and operations that reduce the area of the field subjected to traffic must be implemented

Infiltration rate of a sandy loam soil: effects of traffic, tillage, and plant roots

Settling and trafficking of a soil after tillage causes rapid changes in the soil physical condition until a new equilibrium is reached. In the soil studied, a Wasco (coarse-loamy, mixed, nonacid, thermic Typic Torriorthent) sandy loam, soil compaction reduces infiltration rates, which under grower conditions could result in inadequate infiltration of irrigation water to supply crop requirements. Our objective was to evaluate important management practices as they relate to changes in the infiltration rate of a sandy loam soil. Factors evaluated were traffic, tillage between crops, and the formation of channels by roots of perennial crops. Tillage between crops increased the infiltration rate during the first part of the season in trafficked soils but decreased or had no effect on nontrafficked soil. Alfalfa (Medicago sativa L.) increased the infiltration rate fourfold during a 2-yr period in a heavily compacted soil. An increase in bulk density from 1.6 to 1.8 Mg m-3 decreased infiltration rate 54% in the field. Hydraulic conductivity of undisturbed cores was at least seven times larger than that measured in columns of disturbed soil (same bulk density). This difference is believed to be the result of natural channels in the undisturbed soil that are destroyed when the soil is disturbed. Under controlled traffic, when surface seal is not a problem, tillage will not be necessary to obtain adequate infiltration rates except in the wheel paths

Infiltration rate as affected by an alfalfa and no-till cotton cropping system

Previous studies measured a long-term increase in infiltration rate in a sandy loam soil with time when alfalfa (Medicago saliva L., cv. WL514) was grown. Cotton (Gossypium hirsutum L.) was direct-planted into alfalfa to determine if the high infiltration rates measured under alfalfa culture could be maintained in cotton under either a till or no-till system. Treatments were no-till or tillage to the 0.15 - m depth just before the cotton was planted. Prior compaction levels created by harvest traffic applied to the alfalfa made the soil loose or compacted. Cotton was planted flat and irrigated as a basin. Infiltration rates measured 2 h after water was applied and averaged for the season were 101 (no-till, loose), 56 (till, loose), 82 (no-till, compacted), and 42 mm/h (till, compacted). All the infiltration rates were much higher than normally measured for cotton in these soils. Water flow in the 5-yr-old alfalfa was determined to be mainly through the soil macropore system. High infiltration rates measured in the no-till cotton were also probably the result of flow through the macropores

Crop coefficients and water use for cowpea in the San Joaquin Valley of California

To improve irrigation planning and management, a modified soil water balance method was used to determine the crop coefficients and water use for cowpea (Vigna unguiculata (L.) Walp.) in an area with a semi-arid climate. A sandy 0.8-ha field was irrigated with a subsurface drip irrigation system, and the soil moisture was closely monitored for two full seasons. The procedure used was one developed for cotton by DeTar [DeTar, W.R., 2004. Using a subsurface drip irrigation system to measure crop water use. Irrig. Sci. 23, 111-122]. Using a test and validate procedure, we first developed a double sigmoidal model to fit the data from the first season, and then we determined how well the data from the second season fit this model. One of the results of this procedure was that during the early part of the season, the crop coefficients were more closely related to days-after-planting (DAP) than to growing-degree-days (GDDs). For the full season, there was little difference in correlations for the various models using DAP and GDD. When the data from the two seasons were merged, the average value for the crop coefficient during the mid-season plateau was 0.986 for the coefficient used with pan evaporation, and it was 1.211 for the coefficient used with a modified Penman equation for ET0 from the California Irrigation Management and Information System (CIMIS). For the Penman-Monteith (P-M) equation, the coefficient was 1.223. These coefficients are about 11% higher than for cotton in the same field with the same irrigation system. A model was developed for the merged data, and when it was combined with the normal weather data for this area, it was possible to predict normal water use on a weekly, monthly and seasonal basis. The normal seasonal water use for cowpea in this area was 669 mm. One of the main findings was that the water use by the cowpea was more closely correlated with pan evaporation than it was with the reference ET from CIMIS or P-M.Cowpea Black-eyed peas Crop coefficients Evapotranspiration Irrigation Subsurface drip irrigation Crop water use