Stubble Cover Research Articles

Factors influencing shorebird use of post‐harvest flooded rice fields in California's Sacramento Valley

AbstractBecause of the importance of the Central Valley of California, USA, to shorebirds along the Pacific Flyway, conservation investments have been made in the area's agricultural fields and managed wetlands. Increasingly, landowner incentive programs are being used to deliver shorebird habitat, presenting opportunities to answer remaining questions about which implementation strategies and field management practices are most effective at attracting birds. To provide management guidance for these investments, we collected and analyzed 5 years of data (2014–2018) on shorebird abundance in flooded rice fields enrolled in a dynamic habitat incentive program. The program incentivized flooding in fallow and post‐harvest rice fields in seasons when habitat is relatively sparse, specifically the early fall and late spring. Across nearly 9,000 field observations over 5 years, we explored the relationship between abundance and density (birds/ha) of shorebirds and vegetation cover, soil clay, landscape‐level flooding, and local flood timing, duration, and depth. We observed more shorebirds in fields that were approximately 50% flooded, had water depths of 5–10 cm, and had minimal rice straw or stubble cover, with strong or very strong evidence for each of these relationships. We found that the timing of habitat provisioning was important, with moderate evidence that earlier fall flooding and strong evidence that the duration of fall flooding was associated with higher shorebird density. We observed lower shorebird densities in locations with ample flooded rice habitat in surrounding areas, potentially because shorebirds spread out across the landscape. We found very strong evidence that flooding consistency, either at a site that was continually flooded over many months or a site that had been flooded in previous years, was associated with higher shorebird density. Soil clay content was associated with decreased observed shorebird density, potentially through its influence on the ability of shorebirds to forage for invertebrate prey. These results suggest best practices for shorebird habitat creation in agricultural landscapes, providing important information for conservation and population recovery.

Research Progress on the Effects of Different Soil Methods in Orchards on Soil Nutrients and Fruit Trees

With the continuous expansion of the area of orchards, there are many ways of soil management among orchards. Orchard main line used at home and abroad are covered with grass cultivation, stubble cover, natural grass, fruit intercropping. Different management methods have a great influence on soil nutrient status, root distribution of fruit trees, leaf nutrient yield and fruit quality. In this paper, the main 4 management methods of orchards at home and abroad are summarized: different soil management methods have different effects on soil Nutrients, fruit trees have different effects. This paper analyzes some problems existing in these four kinds of soil management methods and puts forward the problems that need to be solved in the future so as to provide a theoretical basis for exploring suitable soil management methods in orchard of our country.

Does residue cover lead to greater frost damage in barley under conservation agriculture?

Abstract Farmers reported increased frost damage in barley ( Hordeum vulgare ) sown in conservation agriculture in the Mexican Bajío region during the autumn-winter season. To determine whether this effect is real and whether it reduced crop yield under conservation agriculture, we performed two field experiments and gathered observational data from other experiments and farmers' fields. Although more frost damage can sometimes indeed be observed in wheat and barley sown in permanent beds with stubble cover, the data indicate that the plants recover from this damage and that it does not affect yield. Frost damage should not be considered an impediment to adoption of conservation agriculture in the crops grown in the autumn-winter season in the Mexican Bajío.

Effects of harvesting and stubble management on abundance of pest rodents (Mus musculus) in a conservation agriculture system.

The shift to more environmentally sensitive agricultural practices over the last several decades has changed farmland landscapes worldwide. Changes including no-till and retaining high biomass mulch has been coincident increases in rodent pests in South Africa, India, South America and Europe, indicating a possible conflict between conservation agriculture (CA) and rodent pest management. Research on effects of various crop management practices associated with conservation agriculture on pest rodent population dynamics is needed to anticipate and develop CA-relevant management strategies. During the Australian 2020-2021 mouse plague, farmers used post-harvest stubble management practices, including flattening and/or cutting, to reduce stubble cover in paddocks to lessen habitat suitability for pest house mice. We used this opportunity to assess the effects of both harvest and stubble management on the movement and abundance of mice in paddocks using mouse trapping and radio tracking. We found that most tracked mice remained resident in paddocks throughout harvest, and that mouse population abundance was generally unaffected by stubble management. Recent conversions to conservation agriculture practices have changed how pest house mice use cropped land. Management practices that reduce post-harvest habitat complexity do not appear to reduce the attractiveness of paddocks to mice, and further research into new management strategies in addition to toxic bait use is required as part of an integrated pest management approach. This article is protected by copyright. All rights reserved.

Effects of land use-land cover on soil water and salinity contents

Soil salinization due to inadequate land management is considered one of the main threats to the sustainable development of agroecosystems in arid and semiarid regions. Approximately 20% of irrigated areas in the word are threatened by secondary soil salinization. To explore the influence of land use-land cover (LULC) on soil water and salinity in those regions, farmland areas planted with spring-sown wheat (Triticum aestivum L.) or alfalfa (Medicago sativa L.), and bare land (CK) in the Qinwangchuan irrigated region of Gansu Province in China were selected as the research objects. The characteristics of surface vegetation (coverage, height, biomass), surface micro-environmental factors (light intensity, soil temperature) and soil physicochemical properties (moisture and salinity) were measured successively for four years, and their changes and quantitative relationships were analyzed. The results showed that the coverage, height, and biomass of surface vegetation (or stubble) under different LULCs in spring and autumn were significantly different (p < 0.05) and ranked as follows: alfalfa field > wheat field > bare land. With the increasing surface vegetation, the surface light intensity and topsoil temperature at a depth of 5 cm indicated decreasing trends; the water content in the 0–5-cm soil layer showed an increasing trend, while that in the 0–40-cm layers displayed the opposite trend; the salinity at depths of 0–5 and 0–40 cm indicated a decreasing trend. Correlation analysis showed that there was a significant negative correlation between the vegetation characteristics and the salinity in the 0–5- and 0–40-cm soil layers (p < 0.01), while opposite correlations were observed between the vegetation characteristics and the water content in the 0–5- and 0–40-cm soil layers. Regression analysis showed that a 1% increase in vegetation coverage would decrease the salinity at depths of 0–5 and 0–40 cm by 2.5 and 1.0 uS.cm−1, respectively. In summary, farmland planted with spring-sown crops with short growth periods or abandoned in semiarid and arid irrigated regions would gradually experience an increase in soil salinity, whereas the planting of perennial alfalfa could inhibit and lessen soil salt accumulation at depths of 0–5 and 0–40 cm, which is beneficial to improve the soil quality. In addition, this study also revealed the change rule of soil salts under different LULCs in semiarid regions, the fastest increasing stage of topsoil salts, and the importance of surface vegetation and stubble cover in controlling soil salinization.

Hexagonal disc working bodies for working soils subject to wind erosion

Necessary quality of soil cultivation is not always achieved by disk plough-harrows. To solve this problem the improved working unit - flat hexagonal disk was proposed. The aim of the investigation was to determine the dependence of the functional efficiency of the soil tilling implement with flat hexagonal working bodies on its mechanical and technological parameters. The technological process of interaction of the flat hexagonal disk working unit with soil and plant residues was a subject of investigation. To assess the quality of the tillage depending on the approach angle (θ = 15, 25, 35°), machine speed (V = 6, 8, 10 km/h) and processing depth (h = 60, 80, 100 cm) the laboratory tests in the soil channel and field researches at Siberian zonal machine-testing station were carried out. On the surface of the soil channel the stubble cover with weeds was simulated. The ratio of stubble conservation in the soil after the experiment to the weight of stubble used for imitation of the stubble cover served as a criterion of evaluation of the safety of stubble on the surface of the field. The relation of a difference in the weight of mulch, scattered over the soil surface before the test, and that, gathered after the passage of the machine, to the initial weight of mulch was used as a criterion of embedding of vegetative mass in soil. The prototypes of flat hexagonal disc carried out quality tillage with ridgeness no more than 4 cm, the stubble conservation 86…94 %, the chopped straw mass integrity 60 %. Reduction in the presence in soil of erosion-dangerous particles to 1 % allows using flat hexagonal discs in areas exposed to wind erosion

Short-term subsoiling effects with different wing mounting heights before winter wheat on soil properties and wheat growth in Northwest China

The amount of disturbed soil at various depths resulting from subsoilers with different parameters has an important effect on soil properties (e.g. bulk density and moisture content) and crop performance (e.g. crop root and yield). In this study, effects of wing mounting height (h) (from 75 to 155 mm) of the subsoiler under two straw treatments on soil disturbance areas of both hardpan and top layer, soil properties and winter wheat performance were investigated using field experiments. The results showed that reducing h gave a larger soil disturbance area ratio. Based on the ANOVA outputs, soil moisture content, soil bulk density, grain yield in stubble cover (WOS) region and straw yield in both stubble and straw cover region (WS) and WOS region were significantly affected by h at p < 0.05. Reducing h in subsoiling process gave a larger number of winter wheat roots, reduced soil bulk density and increased soil moisture content and grain yield in WOS region, and improved straw yield in both WS and WOS regions. Mean soil moisture contents of the top 40 cm soil (D40) and the top 100 cm (D100) from surface in WS were higher than those of WOS in different stages, except for these with higher soil moisture content with h of 75 mm. Addition of maize straw cover increased straw yield of winter wheat by 8.23% to 25.27% while it had various effects on wheat grain yield under different treatments (h). This study provided critical information for the design of winged subsoilers under two straw treatments in terms of field soil properties and crop performance.

Effects of Cover Crop and Tillage Method Combinations on the Microbiological Traits of Spring Wheat (Triticum aestivum L.)

We carried out multivariate characterisation of phenotypic variability in 27 treatments that were combinations of cover crop, tillage method, and year. Canonical variate analysis was employed to observe nine microbiological traits in an experiment established in a split-plot design. Between 2011–2013, a field experiment was conducted on soils classified as Albic Luvisols. The first-order factor was analysis of the effect of sowing a stubble cover crop: (Control: No cover crop sown; cover crop sown after skimming; no tillage: Cover crop sown directly). The second experimental factor involved evaluating the effects of three tillage methods (direct sowing; simplified tillage to a depth of 12–15 cm with a combined cultivator; spring ploughing to a depth of 25 cm) on nine microbiological traits. The year of research was used as a factor to differentiate between the count and activity of soil microorganisms. The traits (moulds and copiotrophic bacteria, and oligotrophic bacteria and actinobacteria) were significantly correlated (positively or negatively) at all five terms. Pearson’s test confirmed the relationships between the physiological groups of soil microorganisms after the application of organic matter, and captured the positive correlation between moulds and copiotrophs at all terms of the study.

Effects of standing stubble on the interception of soil erosion particles

AbstractCrop residues, particularly standing stubble, can reduce soil erosion by wind in conservation tillage. To determine the optimum architecture of standing stubble for effective reduction of wind speeds near the soil surface, we quantitatively analyzed the interception effect of standing stubbles on soil erosion particles through pure wind experiments and sand‐bearing wind experiments. The relationship between stubble height, row number, and interception rate was also revealed. The study was conducted in a wheat field under conservation tillage. Three representative heights of standing stubble were tested: 10, 20, and 30 cm. All had an average plant density of 400 plants m−2, row spacing of 20 cm, and an average stubble cover of 52%. A wind‐tunnel was placed over the stubble, and the central wind speeds were selected at 6, 9, 12, 15, and 18 m s−1. During the experiments, the blowing time was set for 10 min, and 1,404 g of local soil from the experimental area was fed into the wind‐tunnel. A sand collector was placed at the 16th, 19th, 23rd, 27th, and 31st stubble row away from the air inlet of the wind‐tunnel to measure the amount of soil eroded by wind at different stubble heights under conditions of blank and sand‐bearing winds. The concept of ‘interception rate’ and its corresponding formula were proposed. The interception rates of 10‐cm and 20‐cm high stubbles were lower than those of 30‐cm stubble and decreased sharply, particularly at wind speeds &gt;12 m s−1. Even at the wind speed of 18 m s−1, the interception of wind erosion particles with 30‐cm high stubble at 16th, 19th, 23rd, 27th, and 31st rows were 20.85%, 41.55%, 60.46%, 80.59%, and 85.96%, but only 5.75%, 24.76%, 39.32%, 62.39%, and 76.04% with 10‐cm high stubble at the same positions. The interception effect was similar at the 27th and 31st rows. However, more than 31 rows would be required of the 10‐cm stubble and 20‐cm stubble to intercept the same amount of wind erosion particles as with 27 rows of the 30‐cm stubble. The soil particle interception rate increased with an increase in the number of rows of standing stubble and decreased with an increase in wind speed. As expected, with additional rows of stubble, the amount of soil intercepted increased. Therefore, for a farmland that uses 400 plants m−2, leaves of 30‐cm high stubble with 52% cover, and has row spacing of ≤20 cm, the effective amount of standing stubble should be more than 27 rows.

Soil and Water Conservation Practices in District Swabi, KP, Pakistan

This study is based on survey of the conservation practices adopted by the farmers in various regions of District Swabi (34°10'23" N, 72°34'80" E), (Pakistan). The surveyed area comprised of 86 zones of the District to assemble farmer’s practices for conservation of water and soil. A few reviews demonstrated that over 70% of the world rural areas face direct decline. Water is likewise turning into a rare resource by sedimentation, contaminating with various chemicals. The adoption of a particular conservation practice in any zone seems to have relation with the region’s climatic conditions and land relief. For instance, the practices in Baja (with a relatively smaller slope gradient) were different to that adopted in Utla (with higher slope gradient) where stone walled terracing was the most common practice. Additionally, use of conservation practices were also dependent upon the extent of precipitation and wind, and the regions where precipitation was high, conservation practices were for the most part stubble mulching, cover crops, grass strips, field borders and filter strips that can diminish overflow by improving infiltration. Whilst the areas with higher level of wind erosion were, generally, proliferated with wind breaks and trees plantations. From the results it is obvious that farmers adoptive conservation practices in District Swabi were more focused on decreasing the soil loss, ensuring a safe habitat for natural biodiversity, improving soil fertility and increasing bioenergy production which should help increase financial gains of the farming community living in the area.

Design and experimental validation of sliding knife notch-type disc opener for a no-till combine harvester cum seed drill

One major constraint in developing a combine harvester cum seed drill (CHCSD) is the limited space available for the attachment of no-till furrow openers. Investigating the straw stubble cutting and furrow opening performance of small-sized disc furrow openers is critically important for the development and the optimization of the no-till seeding assemblies. A set of down-scaled sliding knife notch-type disc opener (SKO), modified notch-type disc opener (MNO) and smooth-type disc opener (SDO), with upper size limit of 160 mm, were designed and fabricated for field testing. Experimental results show that for small-sized disc furrow openers of the same type, a larger disc diameter yields a greater furrow depth and width. For small-sized disc furrow openers with an identical diameter, SKOs yield a greater furrow depth and width than MNOs, with SDOs yielding the lowest values. The measured furrow depth and width for an SKO with diameter of 160 mm are 3.52 cm and 3.56 cm, respectively, meeting the no-tillage furrowing requirements for a CHCSD. The highest stubble cover rate of 62.5% is obtained for the SKO with diameter of 160 mm. Therefore, this opener has greater ability to remove stubble from the furrow and seeding band than the other designs. Finally, experimental results of the stubble cutting rates confirm that, for irregularly placed straw and residue, the stubble cutting rate of the SKO with diameter of 160 mm is the highest at 61.7%. Keywords: no-tillage, small-sized, disc furrow opener, furrow type, stubble removal DOI: 10.25165/j.ijabe.20181104.3498 Citation: Qin K, Ding W M, Ahmad F, Fang Z C. Design and experimental validation of sliding knife notch-type disc opener for a no-till combine harvester cum seed drill. Int J Agric & Biol Eng, 2018; 11(4): 96–103.

Effects of wheat stubble on runoff, infiltration, and erosion of farmland on the Loess Plateau, China, subjected to simulated rainfall

Abstract. Soil and water losses in agriculture are major environmental problems worldwide, especially on the Loess Plateau, China. Summer fallow management may help to control soil erosion and conserve water. This study investigated the effects of wheat stubble on runoff, infiltration, and soil loss in laboratory plots under simulated rainfall. The treatments comprised wheat stubble cover (WS) and traditional plowing (TP) in runoff plots (4.0 m × 1.0 m) with three slope gradients (5, 10, and 15°) under simulated rainfall at 80 mm h−1 for 1 h. The runoff volume from WS plots was significantly less than that from TP. The runoff reduction with WS ranged from 91.92 to 92.83 % compared with TP. The runoff rates varied with the runoff volume in the same manner. The infiltration amount was higher with WS (94.8–96.2 % of rainwater infiltrated) than TP (35.4–57.1 %). The sediment concentration was significantly lower with WS than TP. Compared with TP (304.31–731.23 g m−2), the sediment losses were reduced dramatically in WS (2.41–3.78 g m−2) and the sediment loss slightly increased with slope; however, it was greatly increased as slope increased in TP. These results revealed that the stubble cover was the main factor reducing runoff and sediment losses and improving infiltration and that stubble showed a great potential to control erosion and conserve soil and water resources during the summer fallow period in the Loess Plateau region.

Fallow management increases soil water and nitrogen storage

In regions where rainfall during the cropping season is low and variable, such as most parts of Australia, stored soil moisture determines the yield and sowing time of the following crop. A long-season fallow experiment was conducted in south-eastern Australia, and a biophysical simulation model, APSIM, was evaluated and applied. Stubble cover did not significantly affect fallow soil water storage; once the soil profile was filled during the winter fallow, the presence or absence of stubble cover during the summer fallow made little difference. However, weed growth during the summer period significantly affected the soil water storage. By the time of winter crop sowing, the plant available water (PAW) was depleted by 11% (18mm) in weed free – stubble covered treatment, 14% (23mm) in weed free – stubble free treatments, 34% (52mm) in the weedy – stubble covered treatment, and 42% (64mm) in weedy – stubble free treatment. The weedy (39kgha−1) and weed free (98kgha−1) treatments differed significantly in the amount of soil mineral nitrogen at the end of the fallow period. APSIM was able to simulate the change in soil water storage under the weedy treatment accurately (R2=0.93, NRMSE=4%). Long term simulation showed that there was an 88% probability of accumulating 140mm PAW by the time of sowing, compared with only 13% probability when weeds were present. If the summer fallow period was not properly managed, the water stored during the winter season could be lost to weeds. While soil water and nitrogen storage may vary with soil type, rainfall amount, rainfall distribution, and weed pressure, fallow weeds must be controlled to ensure accumulation of fallow soil water and nitrogen for a subsequent crop.

Productivity and the Survival Rate after Winter Management of Seven Tropical Forage Accessions in Subtropical Region of China

Forage production and quality of five tropical grass accessions (Guimu-1 hybrid elephant grass (PG1), Mulato II (M II), Ubon paspalum (PU), hybrid elephant grass (PH) and Reyan 11 paspalum (PR11)) and two tropical legume accessions (Reyan 5 stylo (SR5) and Ubon stylo (SU)) were evaluated in a field experiment in a subtropical area with hot summers and cold winters in Guangxi, China. Three forage stubble cover managements: no cover (CK), dry mass cover (MC) and plastic cover (PC) were applied at the end of the summer period to evaluate cold tolerance and accession survival over the winter. Photosynthesis measurements were taken from the forages in mid-summer. The results showed that PG1 accession produced significantly higher dry matter yields (67.0 t·ha-1) than the other grass and legume accessions. Legume accessions SU and SR5 produced much less dry matter (6.4 - 7.2 t·ha-1) compared to the grasses. M II, PU and PR11 contained the largest proportion of leaf. PG1 and PH showed good cold tolerance (survival rate >85%) under -1°C conditions without any cover management. PR11 had better cold tolerance than PU. M II exhibited very poor winter survival under no cover and with massive cover, and only survived well under plastic cover. The two stylo accessions died completely under all winter cover management treatments. In the growing season, under a given photosynthesis photon flux density (PPFD) = 1500 μmol m-2 s-1, the net photosynthesis rate Pn of all the seven accessions was above 28 μmol m-2 s-1, of which hybrid elephant grass and M II were above 42 μmol m-2 s-1. Though these 7 tropical accessions yielded high production in the grow season, stylo and M II are sensitive to cold in subtropical region of Guangxi. The result suggests that PG1 and PU are good accessions and can be used as productive perennial pasture, while stylo and M II are simply considered as annual one. Additionally, if paspalum was trained in cool region before being introduced to subtropical region, it may present both productivity and enhancive cold tolerance.

The Role of Stubble Type and Spilled Seed Biomass on the Abundance of Seed-Eating Birds in Agroecosystems

Croplands are habitats with high availability of food resources for seed-eating birds. The use of particular fields by birds may vary considerably depending on crop type. Some crop stubbles hold high amounts of spilled grain after harvest, which may support seed-eating bird populations throughout the year. We examined the role of crop stubble type and biomass of spilled grain on species richness and abundance of seed-eating birds in the Pampas of central Argentina. During 2011–13 we sampled 166 stubble fields: 77 fields during the austral spring-summer of 2011–12 and 2012–13 (44 wheat and 33 barley stubbles); and 89 fields during the austral autumn of 2012 and 2013 (49 soybean, 27 corn and 13 sunflower stubbles fields). We recorded birds on a 700 × 100 m transect and estimated spilled grain on 1 m2 of stubble cover in each field. Comparisons among species accumulation curves showed that wheat and barley stubbles had similar bird species richness in spring-summer, whereas in autumn, sunflower stubbles supported higher bird richness than soybean stubbles. Generalized linear mixed models revealed that the abundance of some seed-eating birds had significant associations with crop stubble types. Some species were positively associated with spilled grain biomass on particular stubble types. In general, these associations varied seasonally, being more evident in autumn than in spring-summer. Knowledge of bird species populations and their specific association with given food resources during periods when crops remain only as stubble could be a key tool to help plan management strategies designed to reduce bird impacts on agricultural crops prior to harvest, when they are most susceptible to significant levels of damage.

Sheep grazing on crop residues do not reduce crop yields in no-till, controlled traffic farming systems in an equi-seasonal rainfall environment

In southern Australia, the majority of farms combine a sheep enterprise with a cropping enterprise to form a mixed farming business. Crops are grown in sequence with pastures, and sheep graze vegetative juvenile crops and crop stubble residues after harvest. Recently, growers practicing no-till, controlled traffic cropping became concerned that grazing livestock would damage soil and reduce soil water capture, crop yield and profitability. Sheep grazing on stubbles remove residue cover and compact surface soil, but there is little published research on potential impacts on subsequent crop performance.Two experiments were conducted in high (Temora) and low (Condobolin) rainfall environments from 2009 to 2013 to determine whether sheep grazing crops during the vegetative phase and/or stubbles after harvest damaged soil, reduced soil water capture and storage or affected the performance of subsequent crops. Sheep grazing on stubbles did not reduce crop yields provided summer weeds were controlled with herbicides and at least 70% stubble cover (2–3t/ha cereal stubble) was maintained on the soil surface. Sheep grazing on stubble increased soil strength and bulk density and reduced water infiltration rates, but rarely to levels that were detrimental to soil water capture, crop growth or grain yield. Where reduced infiltration rates did reduce soil water capture, it was due to removal of cover by grazing rather than compaction.Grazing of vegetative crops in winter when soils were generally wet further increased soil strength compared to grazing stubbles alone, but not to an extent that was detrimental to plant growth. Yield effects from grazing crops in winter were not due to soil physical effects, but to differences in plant growth in response to defoliation.Grazing of both stubbles and crops increased the availability of soil mineral N to subsequent crops which increased grain yield and protein in some seasons.The results from these experiments provide strong evidence that livestock can be retained within modern conservation cropping systems without compromising crop performance, and continue to provide the production and business risk benefits for which they have been historically valued.

Contributions of long-term tillage systems on crop production and soil properties in the semi-arid Loess Plateau of China.

This study determined the long-term effect of tillage systems on soil properties and crop yields in a semi-arid environment. Field pea (Pisum sativum L.) and spring wheat (Triticum aestivum L.) were alternately grown in six tillage systems at Dingxi (35° 28' N, 104° 44' E), north-west China starting in 2001. After the first 6 years of experiments, conventional tillage with stubble incorporating (TS) and no-till with stubble cover (NTS) increased soil organic matter by 9.9% and 13.0%, respectively, compared to the conventional tillage with stubble removed (T); both TS and NTS also increased soil microbial counts, available K and P, and total N. No-till with stubble removed (NT), NTS and NTP (no-till with plastic mulching) had 20.7%, 62.6% and 43.7% greater alkaline phosphatase activity compared to the T treatment. Soil catalase, urease and invertase activities were all greater in the no-till treatments than in the T treatment. Averaged across 6 years, both wheat and pea achieved highest grain yields under NTS treatment. No-till with stubble retention is the most promising system for improving soil physical, biological and chemical properties, and increasing crop yields, and thus, this system can be adopted in areas with conditions similar to the semi-arid north-west China. © 2015 Society of Chemical Industry.

Study of sediment movement in an irrigated maize–cotton system combining rainfall simulations, sediment tracers and soil erosion models

Summary Although soil erosion is one of the main threats to agriculture sustainability in many areas of the world, its processes are difficult to measure and still need a better characterization. The use of iron oxides as sediment tracers, combined with erosion and mixing models opens up a pathway for improving the knowledge of the erosion and redistribution of soil, determining sediment sources and sinks. In this study, magnetite and a multivariate mixing model were used in rainfall simulations at the micro-plot scale to determine the source of the sediment at different stages of a furrow–ridge system both with (+T) and without (–T) wheel tracks. At a plot scale, magnetite, hematite and goethite combined with two soil erosion models based on the kinematic wave approach were used in a sprinkler irrigation test to study trends in sediment transport and tracer dynamics along furrow lengths under a wide range of scenarios. In the absence of any stubble cover, sediment contribution from the ridges was larger than the furrow bed one, almost 90%, while an opposite trend was observed with stubble, with a smaller contribution from the ridge (32%) than that of the bed, at the micro-plot trials. Furthermore, at a plot scale, the tracer concentration analysis showed an exponentially decreasing trend with the downstream distance both for sediment detachment along furrows and soil source contribution from tagged segments. The parameters of the distributed model KINEROS2 have been estimated using the PEST Model to obtain a more accurate evaluation. Afterwards, this model was used to simulate a broad range of common scenarios of topography and rainfall from commercial farms in southern Spain. Higher slopes had a significant influence on sediment yields while long furrow distances allowed a more efficient water use. For the control of runoff, and therefore soil loss, an equilibrium between irrigation design (intensity, duration, water pattern) and hydric needs of the crops should be defined in order to establish a sustainable management strategy.

Planting Cotton in a Crop Residue in a Semiarid Climate: Water Balance and Lint Yield

Cotton (Gossypium hirsutum L.) is planted on more land area than any other crop on the Texas High Plains. Much of this area is considered highly erodible and requires a conservation compliance program to participate in government farm programs. Because this region is semiarid and because irrigation water is increasingly limited, water conservation and efficient use of water are necessary to maximize cotton lint yields. One popular conservation compliance practice used is to plant cotton into a chemically terminated small grain crop, i.e., residue that provides wind protection to the cotton seedlings. Our hypothesis was that in a semiarid region the use of a small grain cover crop under irrigated conditions would use more water than it conserves compared to conventional tilled cotton, thus reducing cotton lint yields. To test the hypothesis separate field studies over two growing seasons and on two soil textures, a loamy fine sand and a clay loam, were conducted. The main treatments were tillage systems (conventional and conservation using terminated wheat residue). The two split plot treatments were water supply based on replacement of calculated grass reference evapotranspiration (ETo). Tillage did not affect the amount of water used by the cotton crop at either location ( 0.05) except for an 80% ETo irrigation treatment at a single location where the bare soil treatment used 10% more water than the residue treatments for both years. The residue treatment decreased (P < 0.05) cotton lint yields at both locations by 12% except for the 50% ETo single irrigation treatment in which the residue treatment yielded 14% more lint than the bare soil treatment. The use of terminated wheat residue had no impact on soil water storage during any part of the year. During a 5-month period associated with wheat growth, the wheat evapotranspiration was 20 to 40 mm more water (P < 0.05) than that lost through soil water evaporation from the conventional treatments. The use of terminated wheat residue did not benefit the water balance of the cotton crop, and was associated with decreased cotton lint yields. The results were consistent with our working hypothesis, and disproved the idea that planting cotton into wheat stubble cover increases water use efficiency.

Corrigendum to: Crop-available water and agronomic management, rather than nitrogen supply, primarily determine grain yield of commercial chickpea in northern New South Wales

Chickpea (Cicer arietinum L.) is considered an effective rotation crop in Australia's northern grains region; however, concerns exist that grain yields of commercial crops are reduced because of nitrogen (N) deficiency related to inadequate nodulation and N2 fixation. As part of a program to address these issues, we report on the monitoring of 22 commercial fields around Moree, northern NSW, during 2005–07 that were designated for chickpea, and an associated farmer survey (81 respondents). Our objectives were to determine whether the monitored crops were limited by N and to develop recommendations that would optimise productivity for farmers growing chickpeas. In 2005, only soil water and nitrate data were collected from the six fields designated for chickpea. In 2006 and 2007, almost complete datasets were assembled from the 16 chickpea fields or crops, including soil water and nitrate at sowing, row spacing, plant density, plant height, stubble cover, weed density and composition, shoot biomass, grain yield, nodulation and N2 fixation (%N derived from the atmosphere (%Ndfa) and total crop N fixed). The associated survey provided insights into farmer knowledge of, and practices related to, inoculation. Field monitoring indicated moderate–high levels of soil nitrate at sowing (averages 114, 126 and 110kg N ha–1 to 1.2m depth for 2005, 2006 and 2007, respectively) and generally low plant nodulation (0.11–1.16g fresh wt plant–1) and N2 fixation (0–62%Ndfa and 0–87kg N ha–1). Grain yield varied between 0.53 and 2.91tha–1 across the 14 monitored crops, with averages of 1.89tha–1 in 2006 and 1.02tha–1 in 2007. Although total crop N and grain yields were highly correlated with total (i.e. soil+fixed) N supply, there was no evidence that the monitored chickpea crops were N-limited. Rather, we conclude that soil N and biologically fixed N were complementary in supplying N to the crops, the grain yields of which were primarily determined by the supply of plant-available water (PAW) and water-use efficiency (WUE). Simple and multivariate regression analyses showed that stubble cover during the fallow (positively correlated with sowing PAW) and sowing date (positively correlated with crop WUE) were significant determinants of grain yield. We conclude that farmers could improve inoculation practice by ensuring the time between seed inoculation and sowing is always