Dynamic analysis of competition and complementarity for light and N use to understand the yield and the protein content of a durum wheat-winter pea intercrop

In a previous paper (Bedoussac and Justes 2009, Plant and Soil DOI: 10.1007/s11104-009-0082-2), we showed that intercropping of durum wheat and winter pea increased the yield and protein concentration of durum wheat when early N availability was less than 120 kg N.ha-1. The aim of the present work was to understand these results by analysing intercrop species dynamics for growth, light and N acquisition. A 2-year field experiment was carried out in SW France with different fertilizer-N levels in order to compare wheat (Triticum turgidum L.) and pea (Pisum sativum L.) grown as sole crops and as an intercrop in a row substitutive design. The advantages of intercropping in low N conditions were mainly due to: i) better light use (up to 10%) thanks to species dynamic complementarity for leaf area index and height, ii) growth complementarity over time (higher growth rate of wheat until pea flowering and then of pea until wheat flowering), and iii) dynamic complementary N acquisition associated with better wheat N status throughout growth. Disadvantages, underlining poorer complementarity within the intercrop stand, were observed with ample available N in early growth. This induced higher cereal growth during winter which led to increase interspecies competition by reducing pea light absorption and consequently its biomass production

Durum wheat – winter pea intercropping is efficient to improve the use of environmental resources in low input farming in the French southern conditions

Nitrogen acquisition and grain protein concentration (GPC) of durum wheat is often a major concern, particularly in low input systems where mineral N is a limited resource. In this present paper we assessed the hypothesis that the performance of durum wheat and winter pea, grown in intercrop (IC) is better than in sole crops (SC) for their ability to improve the use of N resources. Field experiment was carried out in SW France in 2005-2006 with three fertiliser-N supply: no fertilizer (N0), 100 kg N ha-1 (N100), and 180 kg N ha-1 (N180). For all treatments, N uptake of durum wheat was significantly greater in SC than in IC but was always lower than the whole IC cover. The nitrogen status (NNI) and the GPC of wheat were higher in IC than SC and obviously increased with N availability. The greatest NNI and GPC of wheat in IC was mainly due to a greater N uptake of soil mineral N per plant. Moreover, the complementary use of soil and symbiotic N2 fixation sources allowed a better N acquisition by the whole IC compared to wheat SC. This advantage was not observed for N180 because fertilizer-N increased wheat growth and induced a reduction of pea growth due to light competition

The efficiency of durum wheat and winter pea intercropping to increase wheat grain protein content depends on nitrogen availability and wheat cultivar

Grain protein concentration (GPC) of durum wheat is often a major concern particularly in low input systems where nitrogen acquisition is low due to limited resource of soil mineral N. By consequence, intercropping (IC) which can improve the use of light, nutrients and water resources (Willey, 1979) could be an alternative to the use of mineral fertilizer (Hauggaard-Nielsen, 2003 and Corre-Hellou, 2006). In this paper, we assessed the hypothesis that the performances of durum wheat and winter pea grown in intercrop (IC) to valorise natural resources are better than in sole crops (SC) in low-input systems. Besides, they would however depend on both nitrogen availability and wheat cultivar

Is durum wheat-winter pea intercropping efficient to improve the use of N in low input farming ?

Nitrogen acquisition and grain protein concentration (GPC) of durum wheat is often a major concern, particularly in low input systems where mineral N is a limited resource. In this present paper we assessed the hypothesis that the performance of durum wheat and winter pea, grown in intercrop (IC) is better than in sole crops (SC) for their ability to improve the use of N resources. Field experiment was carried out in SW France in 2005-2006 with three fertiliser-N supply: no fertilizer (N0), 100 kg N ha-1 (N100), and 180 kg N ha-1 (N180). For all treatments, N uptake of durum wheat was significantly greater in SC than in IC but was always lower than the whole IC cover. The nitrogen status (NNI) and the GPC of wheat were higher in IC than SC and obviously increased with N availability. The greatest NNI and GPC of wheat in IC was mainly due to a greater N uptake of soil mineral N per plant. Moreover, the complementary use of soil and symbiotic N2 fixation sources allowed a better N acquisition by the whole IC compared to wheat SC. This advantage was not observed for N180 because fertilizer-N increased wheat growth and induced a reduction of pea growth due to light competition

The efficiency of a durum wheat-winter pea intercrop to improve yield and wheat grain protein concentration depends on N availability during early growth

Grain protein concentration of durum wheat is often too low, particularly in low-N-input systems. The aim of our study was to test whether a durum wheat - winter pea intercrop can improve relative yield and durum wheat grain protein concentration in low-N-input systems. A 2-year field experiment was carried out in SW France with different fertilizer-N levels to compare wheat (Triticum turgidum L., cv. Nefer) and pea (winter pea, Pisum sativum L., cv. Lucy) grown as sole crops or intercrops in a row-substitutive design. Without N fertilization or when N was applied late (N available until pea flowering less than about 120 kg N ha-1), intercrops were up to 19% more efficient than sole crops for yield and up to 32% for accumulated N, but were less efficient with large fertilizer N applications. Wheat grain protein concentration was significantly higher in intercrops than in sole crops (14% on average) because more N was remobilized into wheat grain due to: i) fewer ears per square metre in intercrops and ii) a similar amount of available soil N as in sole crops due to the high pea N2 fixation rate in intercrops (88% compared to 58% in sole crops)

Thermal exchange effects on steel thixoforming processes

Steel thixoforging is an innovative semi-solid forming process. It allows the manufacturing of complex parts and minimises the forming load. This work aims to identify and characterise the main feature zones of a thixoforging part. The material flow and the forging load are dependent on the thixoforging speed, the tool temperature and the initial temperature of the slug. The data are obtained for C38 thixoforging steel. A specific extrusion tool was designed that integrates the heating of the tool and the slug. This tool was set up on a high-speed hydraulic press. This work highlights the effects of heat exchange on the microstructure, the internal flow and the mechanical characteristics of thixoforging material. These heat exchanges depend primarily on the working speed and tool temperature. The internal flow is composed of three distinct zones. Among them, only semisolid zone is observed during working. The microstructures of thixoforming C38 steel consist of ferrite, pearlite and bainite