Semiarid Dryland Research Articles

Dryland Grain Sorghum Tillering: Clumps vs. Uniform Planting Geometries

When plant populations are reduced to 5.0 to 7.0 plants m−2to conserve soil water, sorghum (Sorghum bicolorL. Moench) forms two to three tillers, but these often produce little grain. We hypothesized that under dryland conditions manipulating planting geometry into clumps spaced 0.75 m apart might result in greater yield by reducing the number of tillers and increasing the percentage of tillers that produce panicles compared with uniform spacing. A field study was conducted during 2007 at Bushland, Texas, with two planting geometries (clump vs. equidistant), two irrigation methods (LEPA vs. LESA) at three irrigation levels (dryland, 50 mm and 100 mm). Clump plants had only 0.6 tillers compared with 1.5 tillers per plant for rows. Tillers accounted for 33% of stover for the equidistant plants but only 23% of the grain under dryland. Our results suggest that growing sorghum in clumps may be a useful strategy in semiarid dryland areas.

Changes in soil physico-chemical properties and microbial functional diversity due to 14 years of conversion of grassland to organic agriculture in semi-arid agroecosystem

Soil physico-chemical properties, microbial biomass, and functional microbial diversity were investigated in two adjacent fields located in a semi-arid dryland farming region of Maharashtra state, India. In organically cultivated field (OCF) large annual inputs of composted cow manure, no tillage and no removal of crop residues is being practiced for the past 14 years. The neighboring plot which was not cultivated for the same period remained as fallow grassland (FGL) served as check for comparison. Soil samples collected from OCF had higher pH, moisture, total organic carbon and nitrogen, microbial biomass, C and N, and enzymatic activities compared to FGL soil. Microbial community structure in the two soils was assessed, using Biolog Eco and GN2 plates. OCF soil showed significant ( P = 0.01) increase of microbial diversity and evenness, suggesting an improvement of functional microbial diversity. Principal component analysis (PCA) separates the two soil samples based on 10 most discriminating carbon sources for each with the maximum positive and negative scores. To the best of our knowledge this is the first study on soil quality and microbial functional diversity of soil in a semi-arid region indicating that conversion from FGL to OCF led to significant soil quality improvement due to the enhanced microbial functional diversity.

Desert knowledge: integrating knowledge and development in arid and semi-arid drylands

Globalisation presents particular challenges for deserts given that their sparse populations, which are amongst the world’s poorest in an absolute economic sense, tend to be remote from major markets and have only a distant, marginal voice in political and policy decision making. Here we are defining deserts as the arid and semi-arid drylands that encompass 70% of Australia and 25% of the world’s land surfaces. The value of the knowledge that local traditions and science have generated about living sustainably in deserts is being promoted and extended through the ‘desert knowledge’ movement in Australia. The Australian research reported here, together with a contribution from Niger that offers a contrast and some lessons for Australia, is largely underpinned by a neopopulist paradigm of development stressing respect for local knowledge, participatory practice and empowerment. Research in partnership with desert Aboriginal groups is contributing to their engagement with new livelihood opportunities. The local knowledge of livestock graziers is also being engaged to support sustainable management of desert water sources and landscapes for multiple values. The research reported here also addresses opportunities and challenges for local norms, identities, knowledge systems, governance and livelihoods from broader scale processes and institutions. In doing so it contributes to a ‘neo-ideographic approach’ wherein desert people might better harness their locality, knowledge and diversity in adaptations that shape their encounters with globalisation. It also points to considerable scope to mature such an approach.

Soil erosion from dryland winter wheat-fallow in a long-term residue and nutrient management experiment in north-central Oregon

Soil property changes resulting from crop production practices are not often readily apparent after a few years or decades. The objective of the research reported here was to evaluate soil erodibility in treatments representing past and current cultural practices in a winter wheat-fallow field experiment established in 1931 near Pendleton, Oregon. Five treatments were evaluated: (1) fall burned residue, 0 kg N ha^-1 crop^-1 (no fertilizer); (2) spring burned residue, 0 kg N ha^-1 crop^-1 (no fertilizer); (3) spring burned residue, 90 kg N ha^-1 crop^-1 (80 lb N ac^-1 crop^-1) commercial fertilizer; (4) residue not burned, 90 kg N ha^-1 crop^-1 commercial fertilizer; and (5) residue not burned, 111 kg N ha^-1 crop^-1 (99 lb N ac^-1 crop^-1) from manure. All treatments were moldboard plowed with multiple subsequent passes with secondary tillage equipment. Weirs, stage recorders, and sediment samplers were used to collect data from January through March of 1998, 1999, and 2000. Grab samples (1 L [0.25 gal]) were collected to confirm digital stage data. Measured soil erosion progressively increased from plots with standing stubble (0.08 Mg ha^-1 y^-1 [10.04 t ac^-1 yr^-1]) to plots in crop with manure and commercial fertilizer amendments with and without the crop residue burned (0.85 Mg ha^-1 y^-1 [0.38 t ac^-1 yr^-1]), to plots in crop with crop residue burned and no fertilizer (3.30 Mg ha^-1 y^-1 [1.47 t ac^-1 yr^-1]). These results provide direct evidence of the relationship between depleted soil quality and increasing erodibility and demonstrate the importance of maintaining nutrient levels in semiarid dryland soils.

Soil erosion from dryland winter wheat-fallow in a long-term residue and nutrient management experiment in north-central Oregon

Soil property changes resulting from crop production practices are not often readily apparent after a few years or decades. The objective of the research reported here was to evaluate soil erodibility in treatments representing past and current cultural practices in a winter wheat-fallow field experiment established in 1931 near Pendleton, Oregon. Five treatments were evaluated: (1) fall burned residue, 0 kg N ha^-1 crop^-1 (no fertilizer); (2) spring burned residue, 0 kg N ha^-1 crop^-1 (no fertilizer); (3) spring burned residue, 90 kg N ha^-1 crop^-1 (80 lb N ac^-1 crop^-1) commercial fertilizer; (4) residue not burned, 90 kg N ha^-1 crop^-1 commercial fertilizer; and (5) residue not burned, 111 kg N ha^-1 crop^-1 (99 lb N ac^-1 crop^-1) from manure. All treatments were moldboard plowed with multiple subsequent passes with secondary tillage equipment. Weirs, stage recorders, and sediment samplers were used to collect data from January through March of 1998, 1999, and 2000. Grab samples (1 L [0.25 gal]) were collected to confirm digital stage data. Measured soil erosion progressively increased from plots with standing stubble (0.08 Mg ha^-1 y^-1 [10.04 t ac^-1 yr^-1]) to plots in crop with manure and commercial fertilizer amendments with and without the crop residue burned (0.85 Mg ha^-1 y^-1 [0.38 t ac^-1 yr^-1]), to plots in crop with crop residue burned and no fertilizer (3.30 Mg ha^-1 y^-1 [1.47 t ac^-1 yr^-1]). These results provide direct evidence of the relationship between depleted soil quality and increasing erodibility and demonstrate the importance of maintaining nutrient levels in semiarid dryland soils.

Winter barley performance under different cropping and tillage systems in semiarid Aragon (NE Spain)

Winter barley is the major crop on semiarid drylands in central Aragon (NE Spain). In this study we compared, under both continuous cropping (BC) (5–6-month fallow) and a crop–fallow rotation (BF) (16–18-month fallow), the effects of three fallow management treatments (conventional tillage, CT; reduced tillage, RT; no-tillage, NT) on the growth, yield and water use efficiency (WUE) of winter barley during three consecutive growing seasons in the 1999–2002 period. Daily precipitation measurements and monthly measurements of soil water storage to a depth of 0.7 m were used to calculate crop water use (ET) and its components. The average growing season precipitation was 195 mm. Above-ground dry matter (DM) and corresponding WUE were high in years with high effective rainfalls (>10 mm day −1) either in autumn or spring. However, the highest values of WUE for grain yield were mainly produced by effective rainfalls during the time from stem elongation to harvest. Despite the similarity in ET for the three tillage treatments, NT provided the lowest DM production, corresponding to a higher soil water loss by evaporation and lower crop transpiration ( T), indicated by the lowest T/ET ratio values found under this treatment. No clear differences in crop yield were observed among the tillage treatments in the study period. On average, and regardless of the type of tillage, BF provided the highest values of DM and WUE and yielded 49% more grain than BC. These differences between cropping systems increased when water-limiting conditions occurred in the early stages of crop growth, probably due to the additional soil water storage under BF at sowing. Although no significant differences in precipitation use efficiency (PUE) were observed between BC and BF, PUE was higher under the BC system, which yielded 34% more grain than the BF rotation when yields were adjusted to an annual basis including the length of the fallow. The crop yield under BF was not dependent on the increase in soil water storage at the end of the long fallow. In conclusion, this study has shown that, although conventional tillage can be substituted by reduced or no-tillage systems for fallow management in semiarid dryland cereal production areas in central Aragon, the practice of long-fallowing to increase the cereal crop yields is not longer sustainable.

Growing Dryland Grain Sorghum in Clumps to Reduce Vegetative Growth and Increase Yield

Stored soil water and growing season precipitation generally support early season growth of grain sorghum (Sorghum bicolor L. Moench) in dryland areas but are insufficient to prevent water stress during critical latter growth stages. The objective of this study was to determine if growing plants in clumps affected early season growth and subsequent grain yield compared to uniformly spaced plants. We hypothesized that growing grain sorghum plants in clumps would result in fewer tillers and less vegetative growth so that more soil water would be available during the grain‐filling period. Results from 3 yr at Bushland, TX, and 1 yr at Tribune, KS, showed that planting grain sorghum in clumps of three to six plants reduced tiller formation to about one per plant compared to about three for uniformly spaced plants. Grain yields were increased by clump planting by as much as 100% when yields were in the 1000 kg ha−1 range and 25 to 50% in the 2000 to 3000 kg ha−1 range, but there was no increase or even a small decrease at yields above 5000 kg ha−1. Our results suggest that planting grain sorghum in clumps rather than spaced uniformly conserves soil water use until later in the season and may enhance grain yield in semiarid dryland environments.

Soil microbial communities of no-till dryland agroecosystems across an evapotranspiration gradient

In degraded agricultural soils, organic C levels can be increased and conserved by adopting alternative management strategies such as no-tillage and increased cropping intensity. However, soil microbial community responses to increased soil organic C (SOC) may be constrained due to water limitations in semi-arid dryland agroecosystems. The purpose of this study was to assess SOC, microbial biomass C (MBC) and community ester-linked fatty acid methyl ester (EL-FAME) composition under winter wheat (Triticum aestivum L.) in no-till systems of wheat–corn (Zea mays L.)–fallow (WCF), wheat–wheat–corn–millet (Panicum miliaceum L.) (WWCM), wheat–corn–millet (WCM), opportunity cropping (OPP), and perennial grass across a potential evapotranspiration gradient in eastern Colorado. Rotations of WWCM and OPP, in which crops are chosen based on available soil water at the time of planting rather than according to a predetermined rotation schedule, increased levels of SOC to those measured under perennial grass. However, MBC under OPP cropping accounted for the smallest fraction (2.0–3.6%) of SOC compared to other systems, in which MBC ranged from 2.4 to 6.3% of SOC. Microbial community structure was most divergent between OPP-cropped and perennial grass soils, whereas few differences were observed among microbial communities of the WCF, WCM, and WWCM rotations. Compared to perennial grass and other cropping systems, microbial biomass in OPP-cropped soil was low and contained less of the arbuscular mycorrhizal fungal biomarker 16:1ω5c. Microbial stress, as indicated by the ratio of 17:0 cy to 16:1ω7c, was greatest under OPP and WCF cropping. In contrast, soils under perennial grass contained lower ratios of bacterial:fungal EL-FAMEs and higher levels of MBC, ratios of MBC:SOC, and relative abundances of 16:1ω5c. Across locations, SOC and moisture content increased as soil texture became finer, whereas trends in MBC and community structure followed the potential evapotranspiration gradient. Soil from the high potential evapotranspiration site contained the lowest level of MBC but greater relative amounts of 16:1ω5c and lower ratios of stress indicator and bacterial:fungal EL-FAMEs compared to soil located at the moderate and low potential evapotranspiration sites. Indistinct microbial communities under WCF, WCM, and WWCM could be explained by EL-FAME limitations to detecting slight differences in microbial community structure or to the overwhelming response of microbial communities to environmental rather than management conditions. Further research is needed to assess potential legacy effects of long-term agricultural management that may mask microbial responses to recent management change, as well as to identify conditions that lead to high microbial community resiliency in response to management so that communities are similar under a given crop despite different preceding crops.

Influence of fallowing practices on soil water and precipitation storage efficiency in semiarid Aragon (NE Spain)

The use of long fallowing (16–18 months) for soil water conservation has been questioned in semiarid drylands of Central Aragon. We quantify the soil water loss, soil water storage (SWS) and precipitation storage efficiency (PSE) of long fallow under three management systems (conventional tillage; reduced tillage; no-tillage). The precipitation storage efficiency of long fallow relative to short fallow (5–6 months) was also evaluated. Over 4 experimental years (1999–2002), the soil water balance was calculated from fallow seasonal precipitation and volumetric soil water content (0–70 cm depth). During long fallowing, primary tillage implemented in conventional tillage and reduced tillage plots induced significant soil water losses from the plough layer (0–40 cm depth) for the first 24 h after tillage. However, secondary tillage appeared to have a positive effect on soil water conservation at the end of fallow. The division of long fallow into three sub-periods showed that the early phase (July to November) was the most efficient in terms of soil water storage. Both for the individual fallow phases and the entire fallow period, the precipitation storage efficiency increased when most of the seasonal effective rainfalls (≥10 mm day −1) were received in the last 2 months of each period. Long fallow precipitation storage efficiency was low (11% on average). Neither soil water storage nor precipitation storage efficiency was significantly affected by the tillage system. The average additional soil water at sowing after long fallow compared with short fallow was 20 mm. Accordingly, the average gain in precipitation storage efficiency of long fallow relative to short fallow was only 5.3%. We conclude that long fallowing might not be suitable for enhancing soil water storage in Aragon.

Study of spatial distribution of sandy desertification in North China in recent 10 years

Sandy desertification is a land degradation characterized by wind erosion, mainly resulted from the excessive human activities in arid, semiarid and part of sub-humid regions in North China. It is one of main kinds of desertification/land degradation as well as water-soil erosion and salinization in China. Rapid and continuous spread of sandy desertification during last 50 years has created a major environmental and socio-economic problem in North China. Remote sensing monitored results in 2000 showed that the sandy desertified land area has been 38.57 × 104 km2. The area of potential to slightly sandy desertified land is 13.93 × 104 km2, moderately land 9.977 ×104 km2, severely land 7.909 × 104 k2 and very severely land 6.756 × 104 km2. Sandy desertification mainly occurs in the semi-arid mixed farming-grazing zone and its northern rangeland zone, semi-arid dryland rainfed cropping zone and arid oasis-desert margin zone. The average annually developmental rate of sandy desertified land increased from 2,100 km2 · a-1 in 1976–1988 to 3,600 km2 · a-1 in 1988–2000. The basic status of sandy desertification in North China is “overall deterioration, while local rehabilitation”. Already achieved rehabilitation results and monitoring assessment show that about 60% of desertified land in North China can be restored under the conditions of rational land-use ways and intensity.

Aggregation of Soil Cropped to Dryland Wheat and Grain Sorghum

AbstractSuccessful and sustainable semiarid dryland cropping depends on effective soil water storage and erosion control, which are influenced by surface soil aggregate size and stability. We hypothesized long‐term tillage and cropping system treatments affect water‐stable aggregate size distribution, aggregate water stability, and dry soil aggregation. A study on a Torrertic Paleustoll from 1982 to 1994 at Bushland, TX, involved tillage methods (no‐tillage, NT; stubble mulch tillage, SMT) and cropping systems for dryland winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] production. In 1994, mean percentages of >4‐mm water‐stable aggregates at 0 to 2 cm were 3.5 with NT and 1.0 with SMT in wheat, sorghum, fallow, rotation phase, or crop comparison plots. Mean percentages of <0.25‐mm aggregates were 49.0 with NT and 37.8 with SMT. More small aggregates with NT help explain why infiltration was 90% greater with SMT than with NT during fallow after sorghum and 26% greater with SMT during fallow after wheat in a similar study on the same soil when surface coverage by residues was limited (25% with SMT, 57% with NT for sorghum; 73% with SMT, 86% with NT for wheat). Aggregate sizes differed due to cropping system, rotation phase, and crop, but aggregate water stability and dry aggregation differences generally were nonsignificant. Both NT and SMT are deemed suitable for dryland crops under conditions as in this study because neither resulted in unfavorable soil conditions or major yield differences.

Root growth of triticale and barley grown for grain or for forage-plus-grain in a Mediterranean climate

Root systems of one triticale (x triticosecale Witt.) and one barley (Hordeum vulgare L.) cultivar grown for grain or for the dual purpose of winter forage-plus-grain were studied in a Mediterranean climate (Granada, Spain). The aim was to assess the effect of winter forage removal on root systems and to improve the knowledge of cereal root systems under Mediterranean conditions in relation to soil water use. After the forage was removed by clipping at the end of the winter period, cereal roots were shallower and lower in length densities, compared to the unclipped treatment. The largest differences occurred during the clipping-anthesis period and in the upper soil layers. At the end of the life cycle, the differences between the two systems regarding depth, density and dry matter of roots were small or nil. Moreover, there were no differences in total water use between clipped and unclipped cereals. Under both production systems (grain and forage plus grain), cereals demonstrated variable downward root extension (0.9 to 1.8 m) as a response to the wetting depth. Triticale roots continued growing after anthesis, especially in the deeper soil layers. In spite of that, root systems were not able to extract a notable amount of residual water (25 to 50 mm) apparently available from the subsoil. In semi-arid Mediterranean drylands, cereal root systems with greater phenotypic plasticity (deeper or larger in the subsoil) in response to subsoil water should be of interest in wetter areas or seasons. This does not necessarily imply a larger root system, but rather a root growth pattern with greater root growth in the subsoil.

Nitrate Leaching in Continuous Winter Wheat: Use of a Soil-Plant Buffering Concept to Account for Fertilizer Nitrogen

Food and fiber production depends heavily on fertilizer N inputs to sustain high yields. Various biological processes in soils and plants have generally restricted grain crops from obtaining N use efficiencies in excess of 70%. Nitrogen that could not be accounted for in N balance studies has often been assumed to have been lost to the atmosphere by denitrification or leached from the system. We evaluated wheat (Triticum aestivum L.) grain yield and soil profile inorganic N (ammonium N + nitrate N) accumulation in four long-term Oklahoma experiments where fertilizer N was applied annually (at a wide range of N rates) for more than 23 yr. Results showed that soil profile (0-8 ft) inorganic N accumulation did not increase until N rates exceeded that required for maximum yield. We suggest that the soil-plant system is able to buffer against soil accumulation of inorganic N. Major buffering mechanisms include increased plant protein, increased plant N volatilization, and denitrification in soil when N rates exceed those required for maximum yield. Annual N fertilization rates that increased soil profile inorganic N accumulation exceeded those required for maximum yields by more than 20 lb N/acre in all experiments. This suggests the presence of a fertilization safety zone with regard to fertilizer N recommendations. Applying more fertilizer N than that required for maximum grain yield did not immediately pose a risk to groundwater quality. The same processes that prevent 100% use of fertilizer N by crops also prevent effective soil accumulation of inorganic N and risk of subsequent leaching to groundwater.

Agronomy of Dryland Corn Production at the Northern Fringe of the Great Plains

The farming systems of the semi-arid northern Great Plains, including the Canadian Prairies, suffer from overdependence on a narrow range of crops, particularly wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). Diversification of economically competitive cropping would greatly enhance the long-term viability and sustainability of agriculture in this large and important region of North America. The expansion of corn (Zea mays L.) production into the coolest and driest fringe of the northern Great Plains (e.g., southern Alberta) represents one attempt at diversification. This expansion has largely been on irrigated land, but semi-arid dryland production of corn appears promising. Eight years of research on dryland corn in southern Alberta focused on hybrid evaluation, irrigated and dryland comparisons, genotypic responses to drought and density stress, optimum plant density, paired row studies, weed control trials, and a 3-yr farm-scale study of three corn-based rotations. Grain yields of 35 bu/acre on summerfallow were obtained with currently available hybrids for the 2840 growing-degree-day (GDD) area around Medicine Hat in southern Alberta. Hybrids that yielded well on irrigation tended to yield well on dryland, and the hybrid most tolerant of stress on dryland had a short anthesis-to-silking interval. Optimum plant densities on dryland are about 12 000 plants/acre, compared with 24 000 on irrigation (annual rainfall of 14 to 16 in.). Dryland yields were more variable than irrigated yields; the lowest yields on dryland were 31 bu/acre (37% of the highest yields), whereas with irrigation the lowest yields were 81 bu/acre (66% of the highest yields). Averaged over five location-year combinations, paired rows (two rows 8 in. apart on 30-in. centers) resulted in a 10 bu/acre advantage over conventional 30-in. rows. The low crop density on dryland allowed late flushes of Russian thistle (Salsola iberica Sennen and Pau) and kochia, [Kochia scoparia (L.) Schrad.] to flourish. A herbicide combination to control this was identified: pre-plant atrazine combined with postemergence 2,4-D. Rotation results indicated that corn after corn yielded 18 bu/acre vs. 35 bu/acre for corn after fallow (similar to cereal yields). Corn shows potential as an alternative dryland crop on the fringes of the northern Great Plains, and may find its place either in a corn-fallow rotation or in a winter wheat-corn-fallow rotation.

EFFECTS OF HOST AND SPATIAL FACTORS ON A HAEMOPROTEID COMMUNITY IN MOURNING DOVES FROM WESTERN TEXAS

Two species of hematozoa, Haemoproteus columbae and H. sacharovi, were observed on thin blood smears from populations of mourning doves (Zenaida macroura) in the Rolling Plains (RP, a semiarid dryland farming and grazing area) and Southern High Plains (SHP, an intensively cultivated and irrigated agricultural region with playa lakes) of western Texas (USA). Prevalences of H. columbae and H. sacharovi were 91 and 18% in doves from the RP (n = 44 doves examined) and 81 and 36% in those from thte SHP (n = 84), respectively. Although the prevalences of these species were not significantly different between the RP and SHP, the prevalence of H. sacharovi was significantly greater in juvenile versus adult doves from both localities. Mixed infections of both haemoproteid species occurred in 11 and 24% of the doves from the RP and SHP, respectively. The frequency distributions of the relative density values (numbers of parasites/2,000 erythrocytes counted) of H. columbae and H. sacharovi were overdispersed in hosts from both localities. Relative densities of H. columbae were significantly higher in mourning doves from the RP versus the SHP; likewise those of H. sacharovi were significantly greater in juvenile versus adult doves and between localities. Observed differences in prevalence and relative density of the two species in the haemoproteid community across spatial and host variables may reflect differences in vector transmission and in the physiological and immunological status of the host. This study emphasizes the importance of using adequately quantified density data versus only prevalence data when examining microparasite communities at the component community level.

Changes in Alfalfa Cultivars Grown in a Semiarid Environment1

Eight alfalfa (Medicago falcata L. and M. sativa L.) cultivars were seeded on a semiarid dryland site in 1954. In 1979 open‐pollination seeds were harvested, plants were excavated to produce synthetics, and seeds of old stocks were obtained for use as check populations to determine if significant changes in adaptive traits had occurred over the 25 years since establishment. Flower color, emergence of seedlings with limited water and from excessively deep plantings, seedling root length, and the recovery and survival of seedlings following a laboratory drought exposure test were evaluated. No significant changes in flower color were found between the checks and the open‐pollination or synthetic populations although a slight tendency for a higher frequency of blue to purple flowers occurred. Seedling emergence with limited water, seedling emergence from excessively deep plantings, and seedling root length were all greater for open‐pollination and synthetic populations than for the check populations. Surprisingly, however, recovery and survival of seedlings following laboratory drought tests were lower for the open pollination and synthetic populations. Thus, although genetic changes have definitely occurred over the 25‐year life of this stand, it is not certain whether these changes were due to natural selection pressures or to the relative reproductive capacities of M. falcata and M. sativa.

Wheat Straw Composition and Placement Effects on Decomposition in Dryland Agriculture of the Pacific Northwest

AbstractField‐measured characteristics of cereal residue decomposition under semiarid dryland agriculture are needed for systematic management of residue in reduced tillage systems. Straw placement, loading rate, and nutrients are all important characteristics. Straw composition and placement, at a moderate loading rate, were evaluated for their effects on decomposition. Wheat straw with three different N and S contents was contained in fiberglass cloth bags which were placed above, on, and below the soil surface to simulate, respectively, standing stubble, straw matted on the surface, and straw plowed under. Weight loss and changes in N and S content were measured during a 26‐month period in a winter wheat (Triticum aestivum L.)‐pea (Pisum sativum L.) rotation. After 26 months exposure residue losses were 25, 31, and 85% for placements above, on, and in the soil, respectively. Above‐surface and on‐surface straw showed a nearly constant decomposition rate with little response to weather variables; decomposition rate of buried straws responded to both soil moisture and temperature. Mineralization or immobilization of N and S were sensitive to placement and initial nutrient content of the straws. Net N mineralization in buried straw varied from 17 to 2 kg N/ha as straw composition varied from 0.78 to 0.20% N. When placed above or on the surface net N mineralizations ranged from 6 to −4 kg N/ha as straw varied from 0.78 to 0.20% N. Net S mineralization paralleled N mineralization, however, magnitudes were smaller. First‐order rate constants for weight loss successfully characterized the placement and straw composition effects.