Influence of pea cultivars on soil N balance and sequent crop production

Non-Peer ReviewedThree field experiments were conducted in northwestern Alberta to determine the influence of pea cultivars on the N economy and the performance of the sequent wheat crop: four pea cultivars were tested with barley as the check. All but one experimental year had below average growing season rainfall. Dinitrogen fixation decreased in the following order among the peacultivars: Grande > Carerra > Eiffel > Swing, the same order as net productivity. Only Grande pea resulted in balanced soil N; soil N deficit, in kg N ha-1, was 7-38 for Carrera, 20-37 for Swing, and 18-37 for Eiffel. Grain N uptake by the sequent wheat was well-correlated with N fixed by pea (r =0.843**). Even where the soil N balance was negative, wheat following pea mostly had higher seed protein content and yield than wheat following barley. The greater N availability after pea is attributed to higher net N mineralization from pea root and rhizodeposits than barley roots and rhizodeposits. It is concluded that selection of a high net productivity pea cultivar should typically result in greater N and yield benefits to the sequent cereal crop than a low net productivity cultivar

Microbial biomass and diversity in roundup-ready corn rhizosphere

Non-Peer ReviewedThe effects of Roundup-Ready (RR) corn, grown in monoculture or in rotation with canola, on microbial biomass and diversity in corn rhizosphere were investigated at Lethbridge from 2002 to 2004. In monoculture, weeds in RR corn or conventional corn were controlled by applying either Roundup or other herbicides. In rotations, RR corn rotated with RR canola or Liberty-Link (LL) canola was compared with conventional corn rotated with conventional canola. Microbiological properties in corn rhizosphere were measured at tasseling stage. In monoculture, RR corn affected microbial biomass only in 2003, when application of Roundup increased microbial biomass in RR corn rhizosphere, but not in conventional corn rhizosphere. The diversity of bacteria in RR corn rhizosphere was greater than that in conventional corn rhizosphere, regardless of Roundup application, only in 2002. RR corn in rotation did not affect microbial biomass or bacterial diversity. Therefore, RR corn affected microbial biomass or diversity in only one of three years when it was grown in monoculture, but there were no effects when corn was grown in rotation with canola. When effects were significant, the rhizosphere of RR corn had greater microbial biomass or diversity that that of conventional corn

Agronomic effectiveness of unacidulated and partially acidulated Minjingu rockphosphates on Stylosanthes guianensis

The majority of soils in Africa are P-deficient, but the high cost of conventional, water-soluble P fertilisers limits their use by resource-poor farmers. Rockphosphates are a low-cost alternative. The relative agronomic effectiveness of unacidulated (RP), 25 percent partially acidulated (PARP25), 50 percent partially acidulated (PARP50) Minjingu rockphosphate and triple superphosphate (TSP) was evalauted at rates of 0-80 kg/ha P on stylo (Stylosanthes guianensis) on an Ultisol in the Ethiopian highlands. The fertilisers were applied once and their effects were followed for 4 consecutive harvests. Stylo dry matter (DM) yields were below 3 t/ha at each cut without applied P and reached as high as 4.8 t/ha when P was applied. Over all 4 cuts, RP was 100 percent, PARP25 was 89 percent and PARP50 was 103 percent as effective as TSP in increasing stylo herbage yields. The corresponding relative responses in P uptake were 103, 79 and 92 percent for RP, PARP25 and PARP50, respectively. The substitution rates for herbage yields were 100 percent for RP, 79 percent for PARPP25 and 106 percent for PARP50 while those for P uptake were 106 percent for RP, 62 percent for PARP25 and 85 percent for PARP50. Significant (P<0.05) effects of P on stylo DM and P uptake were observed at all harvests. It is concluded that raw Minjingu rockphosphate is highly effective on stylo in these soils. This rockphosphate could be used to increase forage production for increased and sustainable crop-livestock productivity on the P-deficient Ultisols

Soil microorganisms and crop yields after cattle manure, hog manure, or fertilizer application

Non-Peer ReviewedSoil biological properties can be significantly impacted by land management. Cattle manure, hog manure or inorganic fertilizers were applied annually or triennially to a Gray Wooded soil at Falher, Alberta, over three years. A control treatment without manure or fertilizer was also included. Canola (Brassica napus) was grown in Year 1, hulless barley (Hordeum vulgare) in Year 2, and wheat (Triticum aestivum) in Year 3. Where effects were significant, cattle manure increased soil microbial biomass C (MBC) by 26-86%, hog manure by 31%, and inorganic fertilizers reduced MBC by 20%. Similar effects, except the reduction by inorganic fertilizers, were observed for functional diversity of soil bacteria (Shannon index, H’). Crop N uptake from hog manure was higher than that in other treatments in Year 1, when hog manure increased grain yields by 75%, cattle manure by 49%, and inorganic fertilizers had no significant effect. However, cattle manure out-yielded other treatments in Years 2 and 3 (25-50% increase over the control) even though N uptake from inorganic fertilizers was the highest in Year 2. This implies that factors other than nutrient uptake also influenced crop yields. Frequency of application usually had no effects on MBC or H’, but the triennial application rate of inorganic fertilizers reduced crop yields relative to annual applications in Year 1

How much phosphorus do crop residues release under conventional and zero tillage systems?

Non-Peer ReviewedIn a field experiment conducted at Fort Vermilion in north-western Alberta, we used the litter bag method to quantify phosphorus (P) release from red clover green manure, field pea, canola and wheat residues under conventional tillage and zero tillage. Wheat residues added significantly less P (1.7 kg ha-1) to the soil than the other residues (5.6-8.5 kg P ha-1). Tillage had no significant effect on residue P applied, but the trend was for slightly greater amounts under ZT than under CT. Clover released the most P (3.8 kg ha-1 under CT and 2.8 kg ha-1 under ZT, compared with 1.4 kg ha-1 or less from the other residues). There were no significant tillage effects on the amounts released by clover, pea and canola residues, but wheat immobilized 0.2 kg P ha-1 under ZT compared with 0.4 kg P ha-1 released under CT. Soil phosphate contents were not significantly different between tillage systems. Phosphate contents decreased with soil depth, especially under ZT. However, there was no tillage by soil depth interaction with canola residues, where soil phosphate was greater (although not significantly) under ZT than under CT at all depths. Uptake of P by wheat was significantly greater where pea and, to a lesser extent, canola residues had been applied than where clover and wheat residues had been applied, and tillage had no significant effects on P uptake

The microbial ecology of a sustainable, long-term lentil-wheat rotation

Non-Peer Reviewe

Decomposition and nutrient release of leguminous plants in coffee agroforestry systems.

Leguminous plants used as green manure are an important nutrient source for coffee plantations, especially for soils with low nutrient levels. Field experiments were conducted in the Zona da Mata of Minas Gerais State, Brazil to evaluate the decomposition and nutrient release rates of four leguminous species used as green manures (Arachis pintoi, Calopogonium mucunoides, Stizolobium aterrimum and Stylosanthes guianensis) in a coffee agroforestry system under two different climate conditions. The initial N contents in plant residues varied from 25.7 to 37.0 g kg-1 and P from 2.4 to 3.0 g kg-1. The lignin/N, lignin/polyphenol and(lignin+polyphenol)/N ratios were low in all residues studied. Mass loss rates were highest in the first 15 days, when 25 % of the residues were decomposed. From 15 to 30 days, the decomposition rate decreased on both farms. On the farm in Pedra Dourada (PD), the decomposition constant k increased in the order C. mucunoides < S. aterrimum < S. guianensis < A. pintoi. On the farm in Araponga (ARA), there was no difference in the decomposition rate among leguminous plants. The N release rates varied from 0.0036 to 0.0096 d-1. Around 32 % of the total N content in the plant material was released in the first 15 days. In ARA, the N concentration in the S. aterrimum residues was always significantly higher than in the other residues. At the end of 360 days, the N released was 78 % in ARA and 89 % in PD of the initial content. Phosphorus was the most rapidly released nutrient (k values from 0.0165 to 0.0394 d-1). Residue decomposition and nutrient release did not correlate with initial residue chemistry and biochemistry, but differences in climatic conditions between the two study sites modified the decomposition rate constants

Rotational diversity effects in a triticale-based cropping system

Research indicates that not all crops respond similarly to cropping diversity and the response of triticale (× Triticosecale ssp.) has not been documented. We investigated the effects of rotational diversity on cereals in cropping sequences with canola (Brassica napus L.), field pea (Pisum sativum L.), or an intercrop (triticale:field pea). Six crop rotations were established consisting of two, 2-yr low diversity rotations (LDR) (continuous triticale (T-T_LDR) and triticale-wheat (Triticum aestivum L.) (T-W_LDR)); three, 2-yr moderate diversity rotations (MDR) (triticale-field pea (T-P_MDR), triticale-canola (T-C_MDR), and a triticale: field pea intercrop (T- in P_MDR)); and one, 3-yr high diversity rotation (HDR) (canola-triticale-field pea (C-T-P_HDR)). The study was established in Lethbridge, Alberta (irrigated and rainfed); Swift Current (rainfed) and Canora (rainfed), Saskatchewan, Canada; and carried out from 2008 to 2014. Triticale grain yield for the 3-yr HDR was superior over the LDR rotations and the MDR triticale-field pea system; however, results were similar for triticale-canola, and removal of canola from the system caused a yield drag in triticale. Triticale biomass was superior for the 3-yr HDR. Moreover, along with improved triticale grain yield, the 3-yr HDR provided greater yield stability across environments. High rotational diversity (C-T-P_HDR) resulted in the highest soil microbial community and soil carbon concentration, whereas continuous triticale provided the lowest. Net economic returns were also superior for C-T-P_HDR ($670 ha–1) and the lowest for T-W_LDR ($458 ha–1). Overall, triticale responded positively to increased rotational diversity and displayed greater stability with the inclusion of field pea, leading to improved profitability and sustainability of the system

Economics of preceding crops and nitrogen application rates for canola and barley production in western Canada

Non-Peer ReviewedThe objective of this study was to evaluate the economic effects of a range of legume and non-legume preceding crops and N rates on costs and net revenue (NR) of canola (Brassica napus L.), barley (Hordeum vulgare L.) and canola-barley rotation under various environmental conditions. Legumes such as field pea (Pisum sativum L.) and lentil (Lens culinaris Medik.) as preceding crop generated higher net revenues for the following crops canola and barley than when wheat (Triticum aestivum L.) and canola were the preceding crops. Although faba bean (Vicia faba L.) grown as a green manure produced the highest annual net revenues for the following crops canola and barley, this contribution was not enough to compensate for the loss of income during the green manure production year. Therefore, growing faba bean as a green manure was not economical. Response of net revenue to N rates was mainly linear or quadratic, and N was optimal at 60 to 90 kg ha-1 at most sites. The results indicate that growing legumes for seed prior to canola can increase net revenues of canola and subsequent barley