Eiko Touno

Evaluation of feeding value of forage soybean silage as a substitute for wheat bran in sheep

Twelve sheep were used in a 3 × 3 Latin square design to evaluate the effect of substituting wheat bran with forage soybean silage in the diet on apparent digestibility and nitrogen balance. Forage soybean (Glycine max (L.) Merrill) was cultivated in a no-till, no-herbicide cropping system with Italian ryegrass (Lolium multiflorum Lam.) as a living mulch. Forage soybean and Italian ryegrass were wilted and ensiled in round bales without additives, respectively. The experimental diets were based on corn silage supplemented with protein sources (tow silages or wheat bran). The crude protein and the acid detergent insoluble protein contents of forage soybean silage were the highest among the protein sources. The apparent digestibility of crude protein and the nitrogen balance did not significantly differ among the diets. In addition, the phytoestrogen content of forage soybean silage was below the level at which animal reproductive performance would be negatively affected. These results suggest that forage soybean silage has comparable feeding value to wheat bran, and can be given at an inclusion level of 17% (dry matter basis) as an alternative protein source to wheat bran without adverse effects on digestion or nitrogen balance in sheep fed a corn silage-based diet.

Arbuscular mycorrhizal colonization increases phosphorus uptake and growth of corn in a white clover living mulch system

White clover (Trifolium repens L.) living mulch, a cover crop cultivation system, has been shown to improve phosphorus (P) nutrition and increase the yield and arbuscular mycorrhizal colonization rate of the main crop without inoculation of fungi. However, it remains unclear whether the P uptake of corn (Zea mays L.) in living mulch is promoted directly by arbuscular mycorrhizal colonization. We performed a pot experiment to test the hypothesis that living mulch increases the P uptake of corn by promoting arbuscular mycorrhizal colonization. The experimental design was a 2 × 2 factorial arrangement using fungicide treatment (fungicide application or no fungicide application) and cropping system (living mulch or no mulch). The fungicide dazomet was used to inhibit arbuscular mycorrhizal colonization. Without fungicide application, the P concentration and dry weight of the corn shoots were greater in the living mulch than in the no mulch treatment, indicating that living mulch improved the P nutrition and growth of corn. Fungicide application in living mulch, however, decreased the P concentration, dry weight of corn shoots, and arbuscular mycorrhizal colonization compared with no fungicide application. These results suggest that living mulch increases the P uptake of the main crop by promoting arbuscular mycorrhizal colonization by indigenous fungi.

White clover living mulch controlled only by mowing supplies nitrogen to corn

Abstract A field experiment was conducted to investigate the effects of white clover (Trifolium repens L.) living mulch controlled only by mowing on the nitrogen (N) nutrition and yield of silage corn (Zea mays L.). Eight treatments were tested: one living mulch treatment without N application and seven conventional cultivation treatments with different N applications (0–200 kg ha−1). White clover was sown in the living mulch treatment in August. The next May, white clover shoots in the living mulch treatment were clipped and left in the field. After tilling the conventional cultivation treatments, corn was sown. At the time when the corn was sown, the N uptake of the white clover shoots was 173 kg ha−1. Measurements at 40 days after the sowing of corn (40 DAS) revealed that the N concentration of corn shoots grown in the living mulch treatment was lower than that in the conventional cultivation treatment without N application. At harvest (123 DAS), compared with that in the conventional cultivation treatment without N application, the N uptake of corn shoots in the living mulch treatment increased by 31.8 kg ha−1. Based on the N uptake and the yield of corn, the fertilizer N equivalencies of living mulch were 62 and 70 kg ha−1 at harvest, respectively. These results indicate that living mulch controlled only by mowing increases the N uptake of corn and may reduce the N application required for corn production.

Potassium nutrient status of corn declined in white clover living mulch.

Abstract We conducted a field experiment to investigate the effects of white clover living mulch on potassium (K) nutrition and the yield of silage corn. We used a randomized block design with a 2 × 3 factorial arrangement of cropping system and K application treatments. The cropping system treatments were: (1) a white clover living mulch (LM) that had been established 10 months earlier, (2) conventional cultivation with no cover crop (CC). The K application treatments were: (1) no K application (K−), (2) K application at sowing of white clover (Kclover), (3) K application at sowing of corn (Kcorn). In the LM treatments, white clover was sown in August 2006. Corn was sown in June 2007. Before the corn was sown, the white clover shoots in the LM treatments were clipped. The three conventional cultivation treatments were then tilled and corn was sown in all treatments using a minimum tillage seeder. In the LM K) treatment, we observed symptoms of K deficiency in corn leaves on 23 July. At the silking stage of corn, the K and N contents of ear leaves in the LM treatments were significantly lower than those in the conventional cultivation treatments. In the LM K− treatment the K content of ear leaves was <1% and the yield of corn shoots was less than that recorded in the other treatments. Multiple regression analyses revealed that K was the nutrient most strongly related to corn yield. These results suggested that white clover LM declined the K nutrient status of corn and as a result decreased the yield of corn.