Above-ground Dry Matter Accumulation Research Articles

Effect of bentonite as a soil amendment on field water-holding capacity, and millet photosynthesis and grain quality

A field experiment was conducted in a semi-arid region in northern China to evaluate the effects of bentonite soil amendment on field water-holding capacity, plant available water, and crop photosynthesis and grain quality parameters for millet [Setaria italic (L.) Beauv.] production over a 5-year period. Treatments included six rates of bentonite amendments (0, 6, 12, 18, 24 and 30 Mg ha−1) applied only once in 2011. The application of bentonite significantly (P < 0.05) increased field water-holding capacity and plant available water in the 0–40 cm layer. Bentonite also significantly (P < 0.05) increased the emergence rate, above-ground dry matter accumulation (AGDM), net photosynthesis rate (Pr), transpiration rate (Tr), soil and plant analysis development (SPAD) and leaf water use efficiency (WUE). It also increased grain quality parameters including grain protein, fat and fiber content. Averaged over all the years, the optimum rate of bentonite was 24 Mg ha−1 for all plant growth and photosynthesis parameters except for grain quality where 18 Mg ha−1 bentonite had the greatest effect. This study suggests that bentonite application in semi-arid regions would have beneficial effects on crop growth and soil water-holding properties.

Effects of chemical fertilizer reduction with organic fertilizer application under water deficit on photosynthetic characteristics and yield of cotton

<p indent=0mm>Fixed position experiments were conducted in 2017 and 2018, and split plot arrangement with the main treatment for full irrigation (W₁) with irrigation amount was 4800 cubic meters per hectare and deficit irrigation (W₂) was 2400 cubic meters per hectare, and the secondary treatment including treatments without fertilization (CK), single application of chemical fertilizer (CF), 75% chemical fertilizer with 25% organic fertilizer (M₁), 50% chemical fertilizer with 50% organic fertilizer (M₂), and 25% chemical fertilizer with 75% organic fertilizer (M₃). The effects of chemical fertilizer reduction and organic fertilizer application on photosynthetic characteristics and yield of cotton were studied to provide theoretical basis for rational utilization of organic fertilizer and reduction of chemical fertilizer input under water deficit. Under deficit irrigation, leaf area index (LAI), net photosynthetic rate (<italic>P</italic>_n), stomatal conductance (<italic>G</italic>_s), above-ground dry matter accumulation and seed yield of cotton were all lower than that under full irrigation, while irrigation water productivity (IWP) and intercellular CO₂ concentration (<italic>C</italic>_i) were higher. The chemical fertilizer reduction combined with application of organic fertilizer could effectively improve the LAI after the full squaring stage, improve <italic>P</italic>_n and <italic>G</italic>_s of cotton in all stage, promote the accumulation of vegetative and reproductive organs dry matter, improve its transfer to the reproductive organs, improve the IWP and seed yield, and also increase the moisture content of soil surface in the period of full boll stage and boll opening stage. The effects among different organic fertilizer treatments on LAI, <italic>P</italic>_n and seed yield were all presented as M₁ > M₂ > M₃, and under the treatment of M₁, the average seed cotton yield of two years increased compared with CF and CK by 6.9% and 62.1% respectively. Whereas, the effects under deficit irrigation were presented as M₂ > M₁ > M₃, and the two years’ average seed yield increased by 19.9% and 79.3% respectively compared with CF and CK under M₂. Chemical fertilizer reduction and organic fertilizer application were beneficial to increase the yield of seed cotton under water deficit, and alleviate the influence of water deficit on cotton growth and development, M₂ (50% fertilizer +50% organic fertilizer) was the best treatment.

Insufficient nitrogen supply from symbiotic fixation reduces seasonal crop growth and nitrogen mobilization to seed in highly productive soybean crops.

Nitrogen (N) supply can limit the yields of soybean [Glycine max (L.) Merr.] in highly productive environments. To explore the physiological mechanisms underlying this limitation, seasonal changes in N dynamics, aboveground dry matter (ADM) accumulation, leaf area index (LAI) and fraction of absorbed radiation (fAPAR) were compared in crops relying only on biological N2 fixation and available soil N (zero‐N treatment) versus crops receiving N fertilizer (full‐N treatment). Experiments were conducted in seven high‐yield environments without water limitation, where crops received optimal management. In the zero‐N treatment, biological N2 fixation was not sufficient to meet the N demand of the growing crop from early in the season up to beginning of seed filling. As a result, crop LAI, growth, N accumulation, radiation‐use efficiency and fAPAR were consistently higher in the full‐N than in the zero‐N treatment, leading to improved seed set and yield. Similarly, plants in the full‐N treatment had heavier seeds with higher N concentration because of greater N mobilization from vegetative organs to seeds. Future yield gains in high‐yield soybean production systems will require an increase in biological N2 fixation, greater supply of N from soil or fertilizer, or alleviation of the trade‐off between these two sources of N in order to meet the plant demand.

Conservation tillage increases yield and precipitation use efficiency of wheat on the semi-arid Loess Plateau of China

Drought is a major limiting factor for rainfed spring wheat production on the semiarid Loess Plateau of China. Suitable tillage practices are important for improving precipitation use efficiency (PUE), which is the ratio of grain yield to annual precipitation. To obtain a better understanding of the effects of conservation tillage practices on PUE on the semiarid Loess Plateau, PUE was divided into five steps: precipitation storage efficiency, farmland water consumption rate, ratio of transpiration to evapotranspiration, crop transpiration efficiency, and harvest index. Six tillage practices were assessed in this paper, including conventional tillage with no straw (T), no-till with straw cover (NTS), no-till with no straw (NT), conventional tillage with straw incorporated (TS), conventional tillage with plastic mulch (TP), and no-till with plastic mulch (NTP), based on a long-term experiment initiated in 2001. The impact of tillage practices on soil quality, soil water storage, soil evaporation, biomass yield, and grain yield of spring wheat were monitored in 2015 and 2016. The results show that NTS improved soil quality and soil water storage before sowing. No-till with plastic mulch and NTS increased evapotranspiration but decreased evaporation, thus optimizing precipitation storage efficiency, the farmland water consumption rate, the ratio of transpiration to evapotranspiration, and crop transpiration efficiency, which gave rise to greater aboveground dry matter accumulation and more dry matter accumulation in grain. As a result, grain yield under NTS and NTP was significantly increased by 45 and 41 % compare to T, respectively, with corresponding improvements in PUE of 43 and 39 %. Therefore, both NTS and NTP have potential to substantially increase grain yield of spring wheat and PUE. However, for sustainable intensification in the long-run, NTS is the best combination of tillage and soil surface management for spring wheat production on the semi-arid Loess Plateau of China.

Root characteristics of individual tillers and the relationships with above-ground growth and dry matter accumulation in sugarcane

Root characteristics of individual tillers and the relationships with above-ground growth and dry matter accumulation in sugarcane

Effects of combined application of pig manure with urea on grain yield and nitrogen utilization efficiency in rice-wheat rotation system

To examine the effects of pig manure application on dry matter production, nitrogen accumulation and distribution, grain yield and nitrogen use efficiency of rice and wheat, the field trial was conducted with wheat 863 and rice 498. Fertilization treatments consisted of seven rates of organic manure supply: control (CK, no chemical nitrogen fertilizer, no pig manure), conventional fertilizing (T1, no pig manure), 2500 kg·hm-2 pig manure with 75% conventional fertilizing (T2), 5000 kg·hm-2 pig manure with 50% conventional fertilizing (T3), 10000 kg·hm-2 pig manure (T4), 15000 kg·hm-2 pig manure (T5) and 20000 kg·hm-2 pig manure (T6). Combined application of pig manure with chemical fertilizer promoted dry matter accumulation of rice and wheat throughout the growing season. At the maturity stage of rice and wheat, the highest aboveground dry matter accumulation presented under highest pig manure input (T6). The dry matter accumulation and nitrogen distribution were enriched in stem or leaf. The dry matter accumulation and nitrogen distribution rate in grain at T6 was significantly lower than T2 treatment. The high-est nitrogen fertilizer partial productivity, fertilizer agronomic efficiency and grain yield of rice pre-sented at T3 treatment, which increased by 11.4%, 55.4%, 11.4% than that of conventional chemical fertilizer treatment, respectively. These vaules for wheat were at T2, which was 14.0%, 29.1%, 14.0% higher than that of conventional fertilizer treatment, respectively. The combined application of pig manure with appropriate rates of chemical fertilizer (T2 and T3) could promote dry matter accumulation, the migration of nitrogen to grains, the increase of yield and the nitrogen use efficiency. Too much pig manure input (15000-20000 kg·hm-2) could lead to excessive supply of nitrogen for crops. In this case, the transportation of dry matter to economic organs would be blocked and the nitrogen enriched to stem. The late-maturing phenomenon occurred, resulting in significant decrease of grain yield.

Soil Matric Potential-Based Irrigation Scheduling to Potato in the Northwestern Indian Plains

A field investigation was conducted in sandy loam soil for two potato (Solanum tuberosum L.) growing seasons (October–January) to standardize the appropriate soil matric potential along with its depth of measurement during 2011–12 and 2012–13. The investigation was conducted under furrow-ridge irrigation system. The treatments comprised three soil matric potential (20, 35, 50 Kpa: (denoted as) S20, S35, S50) and three soil measured depth (20, 30, 40 cm: (denoted as) D20, D30 and D40) and a control (traditional practice) were replicated four times in randomized complete block design (RCBD). Analysis of pooled data for marketable and graded tuber yield, average tuber weight, discarded percent of tubers, root dry weight, plant height and above-ground dry matter accumulation 30, 60 days after planting (DAP) and at harvest favored under S35D20 and S20D20 treatments. Similarly pooled data of Water Use Efficiency (WUI) and Irrigation Water Use Efficiency (WUEi) for S35D20 treatment were more than double that of control treatment along with higher marketable tuber yield, beside 49% irrigation water savings. Our results revealed S35D20 was the best treatment for irrigation scheduling in potato. Conclusively, adopting this threshold corresponded to applying single irrigation two weeks after the complete emergence of crop and remaining 2–3 irrigations at 17 days interval, depending on the effective rainfall and potato growing season in the region.

Effects of tillage practices and microbial agent applications on dry matter accumulation, yield and the soil microbial index of winter wheat in North China

Using microbial agents combined with chemical fertilizers is a promising approach to maintain the soil microbiota balance in continuous wheat–crop rotation fields. Most previous studies focused on microbial agents applied in the topsoil, with limited studies investigating the effects microbial agents under different tillage practices on soil quality and crops growth. In this study, a field experiment was conducted using a two-factor randomized block design (tillage practices and fertilizer applications) with three replicates, the effects of conventional rotary tillage and deep plowing when applying two different types of microbial agents (ETS and JS) on the dry matter accumulation, yield, soil microbial index and soil respiration of winter wheat (Triticum aestivum L.) in north China. The results indicated that wheat grain yield was not decreased after the application of different microbial agents plus 70% of the normal amount of chemical fertilizer and that the straw yield was decreased by 19.1% and 16.4% when ETS and JS, respectively, were individually applied. Additionally, there were no differences in grain and straw yields between the different tillage practices. The aboveground dry matter accumulation increased by 47.5% with ETS application under conventional rotary tillage compared with applications of chemical fertilizer. Under conventional rotary tillage, applications of different microbial agents decreased the microbial biomass C (MBC) concentration by 35.2–42.3% compared with applications of chemical fertilizer, while, the microbial biomass N (MBN) concentration increased by 10.0–18.5% in the 0–20-cm soil layer. With deep plowing, the soil respiration rate was greater than under conventional rotary tillage. In addition, the soil respiration rate after the application of the ETS plus JS combination with deep plowing was greater than after the microbial agents were individually applied during wheat’s growth period.

Artificial warming-mediated soil freezing and thawing processes can regulate soybean production in Northeast China

Northeast China with seasonally frozen soil is quite sensitive to global warming. The changes in soil freezing and thawing processes initiated by global warming could alter the hydrological cycle of agricultural fields. A paired-plot experiment was conducted in frozen agricultural soils in Northeast China to examine the impacts of simulated warming on soil freezing and thawing processes and on soybean production. Infrared radiators were used to simulate global warming, rising surface soil temperature (5 cm depth) by 2.86 °C. We showed that, artificial warming caused the freeze duration shortened by 22 days, and the thaw duration shortened by 17 days resulting in the mean duration of soil freezing-thawing significantly shortened by 39 days and the maximum frost depth reduced by about 40 cm. Simulated warming had no significant effect on the average annual freeze-thaw cycle frequency. Warming induced a larger water accumulation in the 0–100 cm soil layer during 2014–2015 soil freezing period. In the dry year of 2015, warming did not significantly affect surface soil moisture during period from sowing date to VC (soybean cotyledon) date. Thus, warming-induced an increase in soybean yield in the dry year may be attributable to the positive effect of enhanced soil temperature on soybean growth (aboveground dry matter accumulation) and consequent on soybean production. In the wet year of 2014, warming decreased surface soil moisture from sowing date to the date of VC stage because warming advanced the soil thaw-end date in 20–60 cm layer by 15 days. This decline in surface soil water availability may potentially offset the positive effects of increased soil temperature on soybean yield, thus warming effects on soybean production was neutral in the wet year. Our findings highlight the potential role of seasonally soil freezing and thawing dynamics in regulating soybean to global warming and suggested that warming effects on soil water dynamics during soil freezing and thawing periods, and subsequent on the surface soil water availability at the early vegetative stage and soybean production were associated with the hydrological year. We conclude that under current precipitation patterns, the no response of soil surface water availability to warming during early vegetative growth, coupled with warming-mediated increases in soil temperature, might improve soybean production during dry years in Northeast China.

Grain number responses to pre-anthesis dry matter and nitrogen in improving wheat yield in the Huang-Huai Plain

Wheat yield components vary between different ecological regions and yield levels. Grain number responses to pre-anthesis dry matter (DM) and nitrogen (N) in increasing yield were always investigated in spike organs, neglecting the effect of non-spike organ nutrition or overall distribution. This paper determined the relationships between grain number and pre-anthesis DM and N in spike and non-spike organs under different yield levels, with using two sorts of field experiments (different water-nitrogen modes and cultivation management patterns) from 2012–2015 in Huang-Huai plain. The results indicated that improving yield under yield of <7500 kg ha−1 depends on increasing grain number per spike (GNs) or spike number (SN) or both, increased yield under higher yield of >7500 kg ha−1 mainly depends on GNs. GNs showed significant positive relationships with above-ground DM accumulation from jointing to anthesis under high or low yield levels. Rapid DM growth in spring achieves higher GNs. Spike and non-spike DM and N contents both demonstrated strong positive relationships with GNs, spike DM distribution also shows a positive correlation, but spike N distribution ratio show negatively correlation with GNs. Improved N distribution in non-spike organs and DM partition in spike organs conduce to increasing GNs.

Effects of Biochar Application on CO2 Emissions from a Cultivated Soil under Semiarid Climate Conditions in Northwest China

Biochar amendments to soil have potential as a climate change mitigation strategy. However, their effect on carbon exchange in different ecosystems has not been well evaluated. Understanding how biochar affects carbon exchange from agricultural soil is essential for clarifying the contribution of biochar management to the carbon budget. We performed a laboratory and a two-year field experiment to investigate the short- and medium-term effects of biochar application on CO2 emissions from semiarid farmland. There was no statistically significant alteration in the cumulative CO2 emissions from the mixture of soil with biochar alone, while the emissions increased significantly with additional nitrogen amendment over the 46-day experimental period. Over the two-year experimental period, the cumulative CO2 emissions from the field experiment decreased in the biochar-amended treatment, and the effects were significant at high application rates (20 and 30 t·ha−1) relative to the control in the MS. The seasonal CO2 dynamics were strongly dependent on soil temperature, with a higher correlation with the temperature at a depth of 10cm than with the temperature at a depth of 0cm. Soil temperature, rather than soil water content, was the major environmental factor controlling the soil carbon exchange in the semiarid farmland of the Loess Plateau. In general, biochar additions enhanced aboveground dry matter accumulation in both the early and late stages of maize growth. The results suggested that biochar amendment was a preferable management practice to help maintain or increase carbon sequestration for this region with lower CO2 emissions and higher dry matter production over a longer period.

Converting bahiagrass pasture land to elephantgrass bioenergy production enhances biomass yield and water quality

Abstract Changing pasture land to the production of bioenergy crops will affect regional water dynamics. Returning by-products of industrial conversion of bioenergy crops like fermentation residual or biochar back to the field could be used to improve sustainable nutrient management, but could also impact water quantity and quality in ways that are poorly understood. The objective of this study was to assess the effects of land-use conversion from low-input bahiagrass (Paspalum notatum Flugge) pastures to elephantgrass [Pennisetum purpureum (L.) Schum.] for bioenergy production under different nutrient management practices on biomass yield, crop water dynamics and nitrate-nitrogen (NO3-N) leaching during growing and dormant seasons. Treatments evaluated were 1) bahiagrass + 50 kg N ha−1; 2) elephantgrass + 50 kg N ha−1; 3) elephantgrass + 50 kg N ha−1 + fermentation residual; 4) elephantgrass + 50 kg N ha−1 + biochar; and 5) elephantgrass + 250 kg N ha−1. Data were collected on crop evapotranspiration (ET), water use efficiency, drainage, NO3-N leaching, and aboveground dry matter accumulation. Dry matter yield of elephantgrass was 4- to 7-fold greater than bahiagrass after the first growing season, but was similar among elephantgrass treatments. Elephantgrass produced with no residual amendments reduced drainage (approx. 43% across all growing seasons) compared to bahiagrass, and this reduction was exacerbated in the residual treatments. Reduced drainage was associated with increased ET. Elephantgrass, regardless of treatment, reduced the amount of NO3-N lost through drainage compared to bahiagrass. Therefore, replacing bahiagrass with elephantgrass will increase cropping system water use and diminish the rate of groundwater replenishment during the growing season, which could have detrimental effects for other ecosystem processes that rely on this water resource. However, elephantgrass increased the efficiency with which water was used to produce biomass and reduced NO3-N leaching to groundwater.

Regulation of proline biosynthesis and resistance to drought stress in two barley (Hordeum vulgare L.) genotypes of different origin

Drought is considered the main abiotic stress factor that inhibits growth of crop plants (including barley), limiting yield in many regions worldwide. Predicted climate changes show that in future the frequency and intensity of drought events will rise, so crops that are resistant to this stress are in demand. One of the adaptive metabolic responses to drought is the accumulation of proline. The aim of this study was to examine the effect of 10-day drought on tissue dehydration and proline biosynthesis in leaves as well as in roots of barley genotypes of different origin: the Syrian breeding line Cam/B1/CI and the German cultivar Maresi. The involvement of Δ1 pyrroline-5-carboxylate synthetase (P5CS), the expression of the P5CS gene and ABA in proline synthesis under drought were also studied. Finally, we examined the resistance of tested genotypes to applied drought using chlorophyll fluorescence parameters and above-ground dry matter accumulation. Drought caused a gradual decrease of water content and an increase of proline and ABA content in roots and leaves of both genotypes. A statistically significant positive correlation between proline accumulation and activity of P5CS was also revealed. The skyrocketing increase of P5CS activity and proline accumulation was proceeded by transcriptional up-regulation of P5CS. The relationships between changes in P5CS expression, P5CS activity and ABA content show that the latter compound is involved in drought-induced proline synthesis at the transcription and enzyme activity level. The examined barley genotypes were equally resistant to applied moderate drought stress regardless of the differences in the level of proline accumulated.

Compensation effect of winter wheat grain yield reduction under straw mulching in wide-precision planting in the North China Plain

Climate change and the growing demand for food security force growers to identify ways both to improve food production and to reduce agricultural carbon emissions. Although straw mulching is known to decrease CO2 emissions, winter wheat grain yield in the North China Plain was declined under straw mulching. In an effort to determine the most effective way to increase winter wheat yield under straw mulching, a field experiment was conducted using two planting patterns (wide-precision planting and conventional-cultivation planting) and two straw mulching rates (0 and 0.6 kg/m2). The results showed the wide-precision planting/non-mulching treatment significantly increased the leaf area index more than the other three treatments at the early growth stage. This treatment improved aboveground dry matter accumulation and was conducive to increased spike weight in the late growth stage. By contrast, straw mulching significantly reduced winter wheat grain yields by lowering both spike number and 1000-grain weight at the mature plant stage. In the wide-precision planting/mulching treatment, a significantly increased spike number compensated for grain yield losses. The results support the idea that wide-precision planting combined with straw mulching has the potential to decrease the winter wheat grain yield reduction previously observed with straw mulching in the North China Plain.

Comparison of composted biosolid substrate for containerized turfgrass production

Composts produced from composting municipal sewage sludge with bulking agent, namely hazelnut husk (HH), pine litter (PL), corn straw (CS) and sawdust (SW), were seeded with turfgrass mix and cultivated in a container to compare the suitability of composted substrates to produce turfgrass in greenhouse conditions. The performance of substrate was determined by both substrate properties compared to standard peat and by measuring plant growth parameters on each substrate during turfgrass sod establishment. In general, the physico-chemical properties of all substrates were satisfactory for container substrates, but HH and PL substrates performed better in plant growth parameters than in SW and CS composts. The comprehensive growth index values obtained for plants growing in peat, HH and PL were 0.94, 0.87 and 0.84, respectively, which were higher than those in the CS and SW. Plant growth showed linear above-ground dry matter accumulation in all substrates, but was slower in SW and CS. HH and PL substrates appeared to be suitable for containerized sod production for natural soil and peat substitution. Biosolid proved to be an efficient component as a nutrient source ingredient of composted substrates for turfgrass.

Physiological Factors Underpinning Grain Yield Improvements of Synthetic‐Derived Wheat in Southwestern China

ABSTRACTSynthetic hexaploid wheat (SHW) is a valuable source of genetic diversity for germplasm enrichment in wheat breeding. In China, SHW‐derived material has shown significant yield increases. A 3‐yr field experiment at Guanghan and Jiangyou in the Sichuan Basin of China was conducted to characterize the potential of three SHW‐derived cultivars (SDCs) with five local elite nonsynthetic‐derived cultivars as checks (NSCs). On average, SDCs showed an 11.5% or 951 kg ha−1 yield increase compared with NSCs. This yield gain was mainly attributed to increases in both grain number m−2 (5.7%) and thousand kernel weight (5.9%). A higher rate of aboveground dry matter accumulation, especially in the early growth stages, was observed in the SDCs. The SDCs also had better partitioning to the grain, as evidenced through an increased harvest index (HI). The SDCs had a relatively compact and erect plant type with medium and upper leaves having a mean extinction coefficient at 45° (EC45°) increase of 8.4% above the NSCs at 20‐d after flowering. Correlations between grain yield components and physiological traits were analyzed. We concluded that the use of SHW has the potential to significantly increase wheat yield grown under rain‐fed environments with low photosynthetically active radiation.

Relationships among soil respiration, soil temperature and dry matter accumulation for wheat-maize intercropping in an arid environment

Liu, S. B., Chai, Q. and Huang, G. B. 2013. Relationships among soil respiration, soil temperature and dry matter accumulation for wheat-maize intercropping in an arid environment. Can. J. Plant Sci. 93: 715-724. Spring wheat (Triticum aestivum L.) intercropped with maize (Zea mays L.) offers an opportunity to boost grain production in short-season areas, but little is known about the sustainability of the intercropping system. This study, conducted at an arid irrigation site in 2009 and 2010, determined water consumption and soil respiration (Rs) characteristics and their relationships to soil temperature (Ts) and above-ground dry matter (DM) accumulation for wheat/maize (W/M) intercropping compared with sole wheat and sole maize. The W/M intercropping had a co-growth period of 70-80 d, allowing the two intercropped species to complete their life cycles. Maximum DM rate for the wheat in the W/M system was significantly greater than that for sole wheat (57 vs. 51 g d-1), which occurred at around 72 to 77 ...

Relationships among soil respiration, soil temperature and dry matter accumulation for wheat-maize intercropping in an arid environment

Liu, S. B., Chai, Q. and Huang, G. B. 2013. Relationships among soil respiration, soil temperature and dry matter accumulation for wheat-maize intercropping in an arid environment. Can. J. Plant Sci. 93: 715–724. Spring wheat (Triticum aestivum L.) intercropped with maize (Zea mays L.) offers an opportunity to boost grain production in short-season areas, but little is known about the sustainability of the intercropping system. This study, conducted at an arid irrigation site in 2009 and 2010, determined water consumption and soil respiration (Rs) characteristics and their relationships to soil temperature (Ts) and above-ground dry matter (DM) accumulation for wheat/maize (W/M) intercropping compared with sole wheat and sole maize. The W/M intercropping had a co-growth period of 70-80 d, allowing the two intercropped species to complete their life cycles. Maximum DM rate for the wheat in the W/M system was significantly greater than that for sole wheat (57 vs. 51 g d−1), which occurred at around 72 to 77 d after sowing (DAS), whereas the maximum DM rate for the maize in the W/M system was between 31.6 and 44.9 g m−2 d−1, or 30 to 43% lower than that of sole maize. The ercroppedhe umulation of a thetime to reach maximum DM was 96 DAS in 2009 and 80 DAS in 2010 for sole maize, and the corresponding time for the intercropped maize was delayed by 6 to 10 d. Soil respiration and DM was a curvilinear relationship; with the increase in DM accumulation, Rs increased, reached a peak at the early flowering stage for wheat and at the silking stage for maize, and then declined. Soil respiration increased linearly with increases in soil temperature during the growth period for both sole and intercropping, suggesting that farming practices aimed at reducing soil temperature will be effective in reducing carbon emissions. Evapotranspiration during the co-growth period averaged 44.1 mm for sole wheat and 48.5 mm for the intercropped wheat and 57.0 mm for sole maize and 48.0 mm for the intercropped maize, but soil water status had little or no effect on Rs. Wheat/maize intercropping had greater grain yield with lower soil respiration over the corresponding sole plantings, and it can serve as a sustainable cropping system for arid irrigation areas.

Modeling Biological Dinitrogen Fixation of Field Pea with a Process‐Based Simulation Model

Improved prediction of biological N2 fixation by grain and forage legume crops will help the design of more efficient, sustainable agricultural systems. We used field pea (Pisum sativum L.) as an example and focused during model development on inputs that are relatively easy to measure. We propose a new algorithm, which uses the aboveground biomass of legume crops to estimate the N2 fixation rate and have incorporated it into the SPACSYS model. The model was parameterized for field pea and validated against published data from two northern European sites in Dijon, France, and Copenhagen, Denmark. The model simulated the dynamic processes of N2 fixation, N accumulation, and aboveground dry matter accumulation of field pea. Sensitivity analysis showed that N2 fixation at Dijon was very sensitive to low temperature and photosynthetic rate and that a larger green leaf area and faster establishment in young pea plants coupled with a high photosynthetic rate would enhance N2 fixation. We suggest that cultivar breeding aimed at cold resistance and a higher photosynthetic rate could increase N2 fixation under a similar climate.

Crop residue grazing and tillage systems effects on soil physical properties and corn (Zea mays L.) performance

Abstract Crop-livestock systems under no till (NT) could negatively affect soil physical prop-erties and crop performance, due to the additive effects of reduced soil cover and cattle trampling due to livestock grazing, and the absence of tillage. We evaluated the effects of four grazing strategies and of a shallow tillage (ST) on soil physical properties and corn (Zea mays L.) performance for a mollisol after 15 years under crop-livestock systems under NT in Argentina. Grazing strategies evaluated were: closure (C), one grazing (OG), high stocking rate (HR) and farmer’s management (FM), and the tillage systems were: NT and ST. Bulk density (BD), penetration re-sistance (PR), hydraulic conductivity ( k s ), plant population, surface root distribution, aboveground dry matter accumulation, aboveground total N (TN) accumulation and corn yield were evaluated. High stocking rate and FM increased RP. On the other hand, ST decreased PR and BD and increased k s . Corn yield was higher under ST than under NT, and under HR than under the other grazing strategies. Total N ac-cumulation was higher under HR than under the rest of grazing strategies. Rational grazing management and use of tillage systems on resilient soils could have pre-vented soil physical properties be affected beyond critical thresholds.