Description of the experimental site

The experiment was carried out in the summer cycle of 2017 in lot 13 of the Experimental Field of La Laguna (CELALA) belonging to the National Institute of Forestry, Agricultural and Livestock Research (INIFAP) located in Matamoros, Coahuila, Mexico. The municipality of Matamoros Coahuila, is located in the southwest of the state, at coordinates 103° 13’ 4” west longitude and 25° 31’ 41’’ north latitude, its height is 1 110 meters above sea level, it has an average annual rainfall of 258 mm

Prior to planting a sampling was carried out to characterize the soil physically and chemically. 6 random samples were taken at a depth of 0.30 m, these sub samples were mixed to form a composite sample which was sent to the soil laboratory of the Experimental Field (CELALA) for further analysis. The physical and chemical characteristics of the soil of the experimental site are shown in Table 1.

It is a free soil with a tendency to sandy soil (47%), alkaline, non-saline pH, low in organic matter, low in phosphorus and available nitrogen.

Treatments and experimental design

A completely randomized block design was used, six treatments were evaluated with four repetitions per treatment. The experimental plots had an area of 60.8 m² (10 m long and 6.08 m wide). Within each plot, eight rows were formed at a distance of 0.76 m between each one, Table 2 refers.

Variables evaluated

Five variables were evaluated: green forage (FV), dry forage (FS) and grain yield. Foliar nutrient concentration (CNF) and forage quality (bromatological).

Statistical analysis of the data

Statistical analysis of the data was performed using the InfoStat^® student version software (vIS 11-09-017). When there was a significant difference between treatments, a test of comparison of means by minimum significant difference (DMS) was performed.

Soil preparation

Prior to the experiment in the total experimental area, an unfertilized forage oat crop was established with the objective of ‘bleaching’ the soil. The land was leveled with Laser Plane^® equipment to make irrigation more efficient. The plotting of plots, borders and roads was made. The land was fallow with vertical plow, two cross-barking steps were made to later form the plots of the plots and the support edges for the multi-port irrigation system.

Sowing and fertilization

The sowing was done dry on June 28, 2017 with a Gaspardo^® precision pneumatic seeder. The seeded hybrid was Pioneer^® P3966W which is a white grain corn, double purpose and resistant to finishing. One day before sowing, the seed was treated with 500 ml of Tiamethoxam (350 g l^-1 of ia) per 100 kg of seed to avoid damage to the seed by the attack of soil pests. The planting density was 105 000 ha^-1 plants (8 seeds per meter and 0.76 cm distance between rows).

Nitrogen fertilization of all treatments was divided into two, 50% at the time of planting and 50% prior to the first aid irrigation. Phosphorus fertilization (P) was the same in all treatments, consisting of 90 kg ha^-1 of P₂O₅ using phosphoric acid (H₃PO₄, 52% P₂O₅) as a source of P. At 28 days after sowing (dds) carried out a crop or flush with landfills in order to break the ‘crust’ of the soil prior to the second fertilization (50% remaining) and the first aid irrigation.

Watering

The total irrigation sheet (LR) was 89 cm. Immediately after sowing and fertilization, the sowing irrigation was applied through the multi-port irrigation system, an irrigation envelope was made at 7 dds to help the seed to emerge and five irrigation risks as shown in Table 3.

Pest and weed control

Periodic inspections and monitoring of plots in the plots were carried out periodically, especially during critical periods (emergency, flowering and grain filling). The plague that presented with greater incidence was the cogollero worm (Spodoptera frugiperda), observing presence and damage from the emergence of the plants. A ‘salereada’ application of granulated Permethrin (0.4% GR) applied directly to the bud when the crop was 13 dds was made, then three applications of 44.5% Ethyl Chlorpyrifos CE were made. For the control of the same pest at 21, 31 and 59 days, the applications were carried out with backpack sprinkler and the applied dose was 500 mL ha^-1.

With a lower incidence it was presented: eloterous worm (Helicoverpa Zea), red spider (Tetranychus urticae) and diabrotic (Diabrotic spp.). An application of Betacyflutrim (8.4%) + Imidacloprid (19.60%) was performed at a dose of 500 mL ha^-1 for the control of eloterous and diabrotic worm at 50 dds. For the control of the red spider, an application of Abamectin (18 g ia L^-1) was carried out at a dose of 1 000 mL ha^-1 with a backpack spray gun.

Weed management and control was mainly manual with hoes. However, two herbicide applications were made. The first application was made at 34 dds, the product used was Dimethyl amine (2,4 D 49.4% S) for the control of broad leaves at a dose of 1 L of the product in solution in 100 L of water. The second application was made at 51 dds, the product used was nicosulfuron (4.21%) for the control of narrow leaves especially Johnson grass (Sorghum halepense) and wide leaves, mainly quelite (Amaranthus hybridus).

Soil sampling

A soil sampling was carried out prior to planting. Sampling was carried out by means of a box auger. Five random samples were made inside the experimental site at 30 cm depth to obtain a composite sample, the sample was spread over the cardboard bag and allowed to dry in the environment. Subsequently, the sample was ground until it passed through a 2 mm opening sieve. In the soil laboratory of the Experimental Field of La Laguna it was determined: texture, electrical conductivity, pH and the concentration of nitric nitrogen, ammonia and total inorganic nitrogen in extract obtained from 1M KCl and distilled by steam entrainment with MgO and Devarda alloy (^{Cueto et al., 2018}).

Foliar sampling

At 65 days (September 1) when the crop was in the flowering stage, leaf sampling was carried out. 20 plants were taken randomly within each useful plot, two opposite leaves were taken from the cob of each plant which by convention is used for the assessment of the nutritional status of corn. The samples were dried in a forced air oven at a temperature of 65 °C until constant weight was reached. The N was analyzed by the Kjeldahl method. P by the molybdate-vanadate method in visible range spectrophotometer. K, Mg, Fe, Cu, Mn and Zn were analyzed by atomic absorption. The total samples were analyzed in 2018 at the National Soil Fertility and Plant Nutrition Laboratory of the Bajio Experimental Field.

Harvest

When the crop had 104 dds (October 11, 2017), a dry matter content of approximately 33% and the grain was in a phenological state known as a third of the milk line, the experiment was harvested. In each of the plots the four central grooves were harvested, a linear meter was left in each header to eliminate the edge effect such that the useful plot had an area of 24.32 m².

After harvesting the scale and weighing the harvested plants on the useful plot, the total plants, normal plants and hour plants were counted. Five plants were taken from each plot which were labeled and weighed at the time. Subsequently, the plants were sent to the laboratory of the experimental field of La Laguna where they were dried in an oven at 65 ºC until a constant weight was achieved, with this information the percentage of dry matter was calculated. dry matter (%)= dry weight/fresh weight x 100.

Green forage and dry matter yield

The results of the statistical analyzes in the evaluated treatments showed differences only with respect to the treatment of 120 kg N ha^-1 with conventional urea without IN DMPP. The treatment that received 240 kg N ha^-1 in the form of conventional urea without IN DMPP (regional control), was the one that produced the highest yield of green fodder (41.5 t ha^-1) and dry matter (13.88 t ha^-1). However, it was statistically equal to the treatment that only received 120 kg N ha^-1 + IN DMPP. The effect of 3, 4-dimethylpyrazole phosphate (DMPP) on the efficiency of ammonia fertilization in sweet orange and found that the treatment supplemented with IN DMPP improved the efficiency of nitrogen fertilization for the yield and foliar nitrogen concentration variables.

^{Nelson and Huber (2001)} indicate that the potential benefit of the application of IN depends on specific site factors such as soil type, climate, cultural practices and N management programs and that the highest probability of yield response occurs in excessively or poorly drained soils due to losses of N from leaching and denitrification respectively. The results and comparison of means by significant minimum difference are shown in Table 4.

Dry forage yield (FS)

Because the calculation of the FS yield is obtained by multiplying the green forage yield by the dry matter by 100, the results are similar to those of PV. The performance of FS was statistically equal between the regional control (240 kg N ha^-1 UC) and the treatments with the dose of (240 kg N ha^-1 + IN DMPP) and high (360 kg of N ha^-1 UC and + DMPP). These results agree with the data obtained by ^{Cueto et al. (2006)} who in 1998 in a research on forage maize on the effect of population density and nitrogen fertilization found that the best yields of FS were achieved with the dose of 250 and 375 kg of N ha^-1.

It should be noted that there is only a difference of 1.89 t ha^-1 DM between the regional control (240 kg N ha^-1) and the treatment with DMPP IN of 120 kg ha^-1. ^{Barrientos (2016)} conducted an investigation on the effect of the DMPP nitrification inhibitor on N dynamics, yield and quality of forage corn, finding that the best yield was obtained with the dose of 244 kg of N ha^-1 with the IN DMPP and foliar applications of micronutrients and biological compounds.

It should be noted that there was a difference of 2.2 t ha^-1 between the treatment with the lowest dose of N (120 kg ha^-1) with the DMPP IN compared to the treatment with the same dose of N, but without the IN DMPP. The results of the statistical analysis and the means comparison test are shown in Table 5.

Grain yield

The treatment based on 240 kg N ha^-1 + IN DMPP was the one that obtained the highest yield (6.05 t ha^-1) surpassing the regional control (240 kg N ha^-1 without IN DMPP) by 550 kg ha^-1. The increase in grain yield when using fertilizers with the IN DMPP is consistent with the results obtained by ^{Pasda et al. (2001)} who evaluated the effect of IN DMPP on the quality and yield of wheat, corn, potatoes and sugar beets. These authors point out that by using the IN DMPP and dividing it into two applications in the cultivation of winter wheat they managed to increase the yield of grain up to 250 kg ha^-1.

Similar results were obtained by ^{Linares et al. (2012)} who evaluated the effect of fertilization with conventional urea treated with IN in the state of Carabobo in Venezuela. They found that in the treatments where IN DMPP was added they obtained differences of up to 1.2 t ha^-1 with respect to the others, observed in Table 6.

Foliar nutrient concentration

Foliar nutrient concentration

Forage quality