Influence of “Pop‐up” Fertilizers on Soybean Stands and Yield1

Both liquid and granular fertilizers containing nitrogen, phosphorus, and potassium were applied directly in the seed zone of soybeans (Glycine max (L.) Merrill) at planting. An application of 35.5 liters/ha (3.8 gallons/’ acre) of a liquid 5.0-8.8-4.2 (N-P-K) “popup” fertilizer reduced stands by 57.8y0 and yields by 20.3y0. Plant standr: were reduced when only 11.2 kg/ha (10 lb/acre) of a granular 10-15-5 (N-P-K) “popup” fertilizer was applied in the seed zone at planting. Additional index words: Popup fertilizers, Glycine max (L.) Merrill. ’HE placement of fertilizers in relation to the seed 3 of agronomic crops has been studied for many years. Recently, interest has developed in placing a sniall amount of fertilizer in the seed zone at planting as a possible means of stimulating rapid seed gerinination and early seedling growth. Fertilizers which argenerally higher in phosphorus than nitrogen or pcltassium and applied with the seed have become ki own as “pop-up” materials. Previous work has generally been confined to corn ( Z w m a y s L.) with rates of less than 168 kg of material being applied per hectare (150 lb/acre). Both success and failure with “pop-up” materials on corn have been obtained by previous research work and farmer experience (1, 2, 5, 8). Many workers agree that 11.2 kg/ha (10 lb/acre) of nitrogen + potassium (as potassium oxide) is enough for use as a “pop-up” material focorn (7). Limited information is available conce-ning the use of small amounts of fertilizer applied di-ectly in the seed zone for soybeans (Glycine mnx (L.) Merrill). The study reported in this paper was designed to evduate the use of small amounts of liquid and gr mular fertilizers applied directly in the soybean s e d zone at planting. MATERIALS AND METHODS I‘ield experiments were conducted during 1967 and 1968 at several lcications in eastern North Carolina. Table 1 shows the location and soil type for each of the experiments. At each location phosphorus and potassium were applied broadcast according to soil test suggestions, and disked into the toF 15 cni of soil prior to planting. A liquid material (Supplied by Na-Churs Plant Food Compaiiy, Marion, Ohio) containing N, P, and K (5.0-8.8-4.2) was apl’lied at a uniform rate of 35.5 liters/ha (3.8 gallons/acre) at three locations in 1967 and at two locations in 1968. A tworovr tractor-mounted planter was adapted to apply the liquid material through a number 29 Delavan metering orifice at a corstant pressure of 20 psi on top of the seed after they had fallen to the seed furrow but before covering. A second experiment using a granular material (Supplied by International Minerals and Chemical Corp. Skokie, Ill.) containing N-P-K (10-15-5) was conducted at one location in 1967 and at another location in 1968. This material was applied IPaper number 119 of the Journal Series of the North Cai olina State University Agricultural Extension Service, Raleigh, N. C. Received Apr. 30, 1970. Assistant Professor and formerly Assistant Professor of Crop Science, respectively, North Carolina State University, Raleigh, N. C. 27607. I J Y uso oC a granular insecticide applicator that was mounted on a two-row planter. The material was applied directly in the furrow with the seed at rates of 11.2, 28.0, 56.9, and 84.0 kg/ha (10, 25, 50, and 75 lb/acre). A randomized block design with four replications was used at each location. Individual plots consisted of four rows :. paced 96.5 cni (38 inches) apart and 12.2 m (40 feet) long. Plant stand counts were determined in 1.5 m (5 feet) oE ron selectcd at random from each of the two center rows. Seed yields were obtained by harvesting 11.6 m (38 feet) eof the two center rows of each plot with a self-propelled combine. Yield data are based on 14% moisture. RESULTS AND DISCUSSION The use of 35.5 liters/ha of a liquid 5.0-8.8-4.2 (NP-K) fertilizer applied in the seed zone at planting reduced soybean stands by 57.8% as compared to the check treatment during 1967 (Table 2). A similar reduction in plant stand also occurred during; the 1968 season when only visual observations were inade at the two test locations. T h e 57.8% reduction in plant stand which occurred in 1967 resulted in reducing the average yield at the three locations by 63:! kg/ ha. T h e use of the liquid “pop-up” fertilizer resulted in reducing yields by 20.3% when averaged for the five locations during 1967 and 1968. These results indicate that germinating soybean seeds are severely affected by very low rates of liquid fertilizers when placed in the seed zone at planting. The 35.5 liters/ha fertilizer rate used in this experiment contained 5.0, 8.8, and 4.2% of N, P, and K, respectively. Using a weight oE 1.82 kg/liter for the liquid fertilizer, the amounts of N, P, and K applied per hectare were 2.34, 5.00, and 1.97 kg, respectively. The combined nitrogen and potassium rate of 4.31 kg/ha used in this experiment is considerably less than the rate found to be beneficial for corn prciduction (7). The data in Table 3 show the influence of a granular “pop-up” fertilizer on soybean stands and yields when applied at rates of 11.2, 28.0, 56.0, and 84.0 kg/ha. A reduction in plant stand was obtained when Table 1. Location, soil type, and form of “pop-up” fertilizer used on soybeans in eastern North Carolina (1967-68). Ferti l izer form Year county soil type Edgecombe’ Wagram fine sandy loam liquid 1967 Liquid 1967 Edgecomhe Dunbar fine sandy l m m Pender Lynchburg fine sand] loam Idquid 1967 1iquid 1968 Wake* liquid 1968 Pender Lynchburg fine sandy loam Granular 1967 Edgecombe h i b a r fine sandy h i m Granular 1968 washington * Tost located on individual fa rms with leading soybean producers, other tests located on Agricultural Experiment Stations. Appling sandy loan1